92 hard to start when hot

Here sometime back I had trouble out of my EGR Valve. 1st time it got to where it was had to start.

The EGR was stuck, so I cleaned it and put it back on, worked for a while, finally I had to replace it.

Now I'm once again having trouble, thought at 1st that maybe it had stuck open again, but it wasn't.

When cold it starts great, but when its hot it will not. I've noticed if I will hold the throttle wide open before trying to start it when its hot it will start, but runs rough for a few minutes.

But if you don't hold the throttle open, it will just crank and crank not even trying to start.

Any ideas would be appreciated.

Oh, its had 2 fuel pumps put on it.

Sounds like its flooding. Holding the pedal to the floor puts the truck's PCM/ECM into flood clear mode, and stops the injector from firing and throwing gas in the engine. With it running rough after it starts, it sounds like its just buring the extra fuel. When its cold it needs the richer mixture, plus it sits for awhile so some gas evaporates and it starts without problem.

I would pull the upper intake and look for leaks. With key on engine off, let it prime and see whats there. If you see no leaks at this point, fire the injector manually by jumpering the injector from the battery, and see if you have leaks at the nozzles, and/or the little tubes.
Good Luck!

I agree with Blazes,
After removing the top, it's supposed to be grungy inside. Any bright, clean areas are where fuel is leaking or spraying. Clean passenger side area is a fuel regulator problem. Clean drivers side area is a supply or return fuel supply problem.
Here's some pressure regulator replacement pics.
http://www.automotiveforums.com/vbulletin/showthread.php?t=518850&highlight=cpi+regulator

I thank both of you for your replies. I meant to get back sooner then this got thank you for the information.

In the old days I did quite a bit of work on Chevy's, back when they had points and Rochester Quadrajet Carburetors. But the modern day computer and fuel injected engines are foreign to me.

But I have seen the inside workings, had to replace the gas line to the spider about 30,000 to 40,000 miles back. At that time I did have a friend who run codes on it 1st, but there were none, he suggested what y'all have, take the cover off and check the lines and such.

I did go look at your fuel regulator replacement pictures.

Yesterday I talked to a person, who gave me basically the same information as you 2 have, but he did say, I would run codes before talking off the cover and checking the spider.

Last night I was going to call my friend and ask him if he could run code on it this weekend, but he has since divorced and has no telephone and now works out of town, so that may not work out.

I might add, when 1st started it idles fairly well. But after I drive it to town the idle is a bit rough. And as I previously said, if you kill it and come back in a short time the only way it will start is to hold the accelerator to the floor. When it starts you can smell much gas from the exhaust.

The for a few seconds you have to hold it above idle or it will die, especially if you put it in gear.

My gut feeling was that it is the spider.

I did order a top gasket set yesterday, for here in rural Arkansas usually its not in stock and has to be ordered.

From what I gather yesterday talking to my parts man, the spider and fuel pressure regulator comes as one unit, the price was a bit over $350.00. I had been told a few years back that they were around $550.00 to $600.00.

Out of curiosity, do you know how many years models used this spider set up like the 92 S 10 Blazer?

The spider unit used in these trucks was used from approximatley '92 to '95. They were used in the s-10's, astro/safari vans, and of course blazer/jimmy's that had the W engine code.

For sure get it scanned, you have to see whats going on there. From there take a look at the spider unit, if all that checks out it could be a 02 sensor, or even the ECM itslfe that starting to go out.

Good Luck!

Double check all basics.
For checking codes.
http://www.troublecodes.net/GM/
If you get any codes post back code no.
A fuel pressure check and test will help pinpoint a leak in the injector system.
Watch for a fast leak off on fuel pressure.
If it is leaking in there when you get the cover off prime up fuel pressure and look for the leak.
They can leak at the fuel pressure regulator or the plastic fuel feed and return lines called a fuel line nut kit.
MT

Right on the fuel nut kit, replaced it a few miles back, the one coming in was split and spraying gas everywhere.

Went to my friends house, had his old computer at home. Guess what, it pointed to the spider.

Did not have his fuel gage at home, it was 30 miles away where he works. His old computer doesn't show fuel pressure.

Probably early next week I will put the cover. He told me if I did not see a leak to call him at the shop and he would bring some equipment and come out here to check it further.

Thanks again for the help. When I find more out I will post it, maybe it might help someone.

I pulled the top intake yesterday. It was leaking real bad from around the regulator.

Which I had started it and moved it to another location, as soon and I took the breather loose I could smell gas fumes real strong. If someone has a similar problem in the future, if they will unhook the flexible rubber tube on the intake they can probably smell the excess gas that's under the intake. The fumes from mine would nearly knock up down.

I'm going to replace the injector, having more than 146,000 mile on it and planning on keeping it for a few more years, I feel that is the smart thing to do while I've got it opened up.

I'm going to go ahead and replace the fuel lines, I believe y'all have said GM calls it a nut kit, that hooks to the injector, I believe that when my friend replaced the incoming line, it split about 50,000 miles back, that he only replace the fuel incoming line, not the return line, seems silly to me not to replace both of them while I've got it opened up.

I bought it new in 92, I'm still not ready to get rid of it, its been a very good ride, drives and rides like new and I feel it drives better than our 2002 Jeep Grand Cherokee.

About the only thing rightly wrong with it is in the last 3 to 4 years the white paint has been turning loose, which I suppose I'm fortunate, for I know many of the white ones did this in the 1st few years they were on the road.

When my friend had the computer on it, at 1st the temperature was running at about half of what it should. After a bit it jumped back up running normal. So while I have the top intake off I'm going to go ahead and change the sending unit located on the front left hand side of the motor kind of below the EGR valve. Be much easier to change it while I have the top intake off. I understand this sending unit goes only to the computer.

I went to the code page posted, I sure didn't know you could take a paper clip and or a jumper wire and read codes on at 92 S-10 Blazer. I appreciate that info, thanks for posting it.

Here is the code page again.

http://www.troublecodes.net/GM/

But I don't see no code listing for my 92 4.3 Multi Port Fuel Injection with a W motor. Am I missing something something?

Is yours a S-10 or a S-10 blazer. One or a S-10 does not list a W engine until 93.
A L35 engine.
But no problem.
Just use the 93 W engine codes.

And I thought I had Blazer in my signature, but I didn't. But its there now for I went and added it right quick.

Don't remember where I saw it, but the other day I was doing some searching and I read something that said the 92 S-10 Blazer's 4 X 4, the biggest majority had the throttle barrel system.

From what I here it doesn't get as good of fuel mileage and doesn't have as much power as the multi-port fuel injected engines.

So mine is the same as a L 35 engine in a 93 model.

I'll see what it does when I get it put back together, my parts are suppose to be here sometime after dinner tomorrow.

I was surprised me, in less than 45 minutes I had the injector out.

Parts came in today, they are installed and my old Blazer runs better than it has in quite some time, nearly like a new one. :grinyes:

Injector kit and nut kit were from Delco. They came out of Memphis, TN, ordered yesterday morning, got here about 11:00 AM this morning.

Injector kit 393.93
Nut kit 75.16
Temperature sending unit 17.59
Gasket 9.64
shipping charge 9.50
taxes 46.66

Total $552.84

The worse part of it was getting the fuel lines coming into the back side of the intake started. Thought I would never get them. I finally slid them things out the back side of the intake, got them started, them slid them back in and them all went well.

If I were to do it again and or telling someone the best way to do it, I would get them started before sliding them in the backside of the intake. I would have saved probably more than 45 minutes if I had known that.

Thanks much for the help, appreciate it so much. Especially the pictures that were posted, that in itself is worth so much when tearing into something like this.

You are welcome and.
Thanks for posting the fix and how it went.
Glad all is well now.
MT

Do you have trouble with those fuel lines coming in the back side of the intake?

I did not mention it, but I did grease them down right good as well as the hole they go into hoping to prevent cutting or nicking the O-rings.

I learned to do that when I was a jet engine mechanic in the Air Force back in the last half of 1965. I found that would prevent many headaches caused from tearing things down a 2nd time and putting them back together again. The 2nd time was never as enjoyable as the 1st time.

This is much like the trouble that I'm having with my 92 S-10 Blazer is doing.

Not that many miles back I replaced the injection spider, The story is right here (http://www.automotiveforums.com/vbulletin/showthread.php?t=697448), everything worked great for a while, now at times when I start it, I have to use starting fluid, although at times it starts OK. After it has been started I drive to town it starts just fine.

Yet last week another problem showed its face. It started idling to high. I checked to see that the accelerator was not sticking inside or under the hood, and it wasn't. So I started unhooking sensors one at a time, the 1st one was the one across for the throttle valve. Just a few short seconds it idled back to normal.

I went and talked with my favorite parts man, he suggested taking the sensor off and clearing it up as necessary before buying parts. I had not idea what the sensors looked like on the other side. So I took the one on the throttle off 1st, there was nothing to clean on it. Them I took the one off on the accelerator side. It was a bit dirty and I cleared it up. The other 2 it did not seem there was anything I could do for them.

After doing this it started fine, and idled properly, so I leave it to try today and see what happened. Same thing, had to use starting fluid to get it started, after it started it idled to high, I unhook the sensor across for the accelerator and it idles just fine. Seems to run a OK.

Could these 2 problems be connected? Thought I would ask before I went any further.

Since this topic was so much like mine, I thought I would 1st post it here, them go from there.

Using starting fluid is dangerous and can damage the engine, best to use carb spray instead.

If it starts when doing this, it's a classic symptom of low fuel pressure or excessive leakdown, or both. Ignition ON, engine OFF, fuel pump running, fuel pressure must be 55psi to 61psi and must remain above 50psi for 3 to 5 minutes after the pump shuts off. Post your results.

Thanks much for the quick reply and the information sent in the PM, I do appreciate it.

I'm just speculating.

My fuel spider has about 8,000 miles on it, my fuel pump has about 12,000 miles. I would suppose that it should still be good for in this time the engine has never been hot, in fact I bought my 92 Blazer new in 92 and its never overheated, so it has not been exposes to extreme heat nor been abused. One would think with all this having been replaced I would not be having trouble with them this soon. Yet we all know that even new parts can go bad quickly at times.

That said it seems my best move and only move is to get a fuel pressure gauge and make theses checks, them I will know what I'm looking at.

If the pressure regulator on my injector assembly happens to be bad, can I just replace it?

Yes, the regulator can be serviced separately. Run the test and post the results before replacing any parts.

I ordered the gauge you referred to, received it today, but the gauge is faulty, it fills up with gas and them the gas runs everywhere.

I did do this, of course with the faulty gauge one can't be positive of the results.

Turn on key, pressure goes up, yet quickly falls to zero. I tried this 3 or 4 times, same result.

I did start the engine for a few moments, had to use starting fluid of course, which with fuel gauge as is one can't be sure of accuracy, pressure fluctuated from 50 to 54 pounds. Which I did not let it idle but for maybe 25 to 40 seconds.

I've contacted Harbor Freight, now we will see just how good Harbor Freights customer services is.

So now I'm still playing the waiting game.

Autozone and Advance Auto Parts rent/loan them if you don't want to wait.

Harbor Freight has a place at Texarkana, TX, a bit over 50 miles away. Today my wife had a doctor appointment down there so I went by their store, exchanged this fuel pump tester with out problems whatsoever. This one works great.

My pressure is low when the engine is cold, about 48 pounds. I turned the key on and off several times, still the pressure was at 48. Of course for it to start properly it has to be 55 or better, so I at least know I've got a problem somewhere in my fuel system.

After I started it using starting fluid, let it warm up, them killed it, the pressure was setting on 62 pounds, and of course it starts great them. Running pressure at idle is about 52-53 Pounds.

I might say after its been started and warmed up it starts OK. I've started it several times now with starting fluid and went to town and have been out of it as long as a couple of hours and it started OK.

I'll have to get me a set up to put in place of my fuel filter in order to finish checking out my system. I think we have a forecast of rain in the next day or 2, if so being as my workshop's roof is the sky, that may hinder this old man.

I meant to say earlier I know that starting fluid can be dangerous and appreciate you mentioning that fact, I drove a truck up through the late 80's until a back injury forced me to stop. I always made sure to have a can of starting fluid with me at all times. It saved my day many times and I've know of many truck drivers that were quite happy that I had a can of it. Old habits are hard to break, I generally always have a can of it around the place, just in case.

And thanks again for your advise on this subject.

When fuel pressure drops below approximately 50psi, there isn't enough pressure to open the poppet valves and they won't squirt fuel. If it starts when adding fluid, that's a classic symptom of low pressure, which you confirmed. After the engine is running, available voltage at the pump increases and that's probably enough to bring fuel pressure above 50psi. If the pressure does not leakdown after the pump shuts off, and the voltage and ground at the pump are OK, the pump needs replacement. If that's the case, fuel pumps are not a place to cut corners, use an AC Delco or Delphi pump.

Oh boy the fun begins, I just love where they place fuel pumps nowadays. Its such a joy to drop the fuel tank on a Blazer S-10. At least this time I will not have a full fuel tank to deal with. On the last one I had just filled up them drove about 15 miles.

Got one ordered, this time I'm replacing the whole assembly even though it cost several dollars more for since last time my gas gauge has not worked quite right and this will be the third fuel pump.

Any tips on getting my fuel lines started? In 2005 they were a bit of trouble, but much more now than them. When I get the fuel lines started I'll be headed for home plate.

New fuel pump fixed part of my trouble. Fuel pressure 60 # when ignition switch turned on and my old blazer starts very good. Appreciate all advice given.

At 1st I thought my fast idle was fixed too. I started it 3 or 4 times, did great, them I let it warm up, idled perfectly.

When on a test run to town & to fill up my gas tank, when I pulled into the convenience store it was back idling quite fast, not so fast that it would be dangerous to drive but yet aggravating. Outside of the fast idle it runs just fine.

I can unplug the lead to the Throttle Position Sensor and it idles down perfectly.

I recently took the IAC valve off and cleaned it up, I did not test it to see if it was operational, I wanted to be sure it was safe to do so before using jumpers on it.

Any advice would be appreciated.

Could be a problem with the throttle position sensor. It's possible for it to indicate too high of voltage but not turn the check engine light on. With the engine at idle, the dark blue wire at the throttle position sensor should show approximately .5VDC Check it and post your results.

OK, thanks, probably be next week before I can check this. I've got some things to catch up on after fooling with this fuel pump nearly all week.

Changing fuel pumps is not a great job for someone that's had several neck surgeries.

Guess I should have said I do not have no check engine lights burning. Sorry.

Thought I would mention this, maybe it will help someone.

When I 1st got everything hooked back up I had a big scare. When I turned on the ignition switch my fuel pressure went to + 60 #'s, but quickly dropped to 25 #'s.

I thought, oh no, a bad fuel pump. I turned the switch on and off several times and it did the very same thing. I tried starting it, it cranked right up. I let it run a few minutes, them kill it, fuel pressure drops to 25.

I hit the started, it cranks right up. I'm scratching my head thinking it should not start, there is no way this is right. After about 30 minutes with no change I take a break. During this time I think about my ground wire, I had hooked it up at a different place from where it had been, for it was hard to get to and I had just cut the ground wire when taking the old pump off for here at my age and condition my hands will not work in tight places.

Finally I decided, I going to take the bolt out where my old ground wires was hooked and move the new ground wire to there. With much frustration taking that old bolt out, moving my ground wire, I crawl out from under my blazer and go turn on the key, bingo, 62 #'s of fuel pressure, hit the starter, starts great.

I fail to understand why it did not get a good ground where I 1st hooked it up, yet one thing is clear, for some reason it did not. Sometimes we forget how important the ground wire is and just because it is tightly bolted to a portion of the frame does not mean its grounded good. I'm just glad I thought about it and did not pull the tank back off.

Thought I would mention this, maybe it will help someone.

When I 1st got everything hooked back up I had a big scare. When I turned on the ignition switch my fuel pressure went to + 60 #'s, but quickly dropped to 25 #'s.

I thought, oh no, a bad fuel pump. I turned the switch on and off several times and it did the very same thing. I tried starting it, it cranked right up. I let it run a few minutes, them kill it, fuel pressure drops to 25.

I hit the started, it cranks right up. I'm scratching my head thinking it should not start, there is no way this is right. After about 30 minutes with no change I take a break. During this time I think about my ground wire, I had hooked it up at a different place from where it had been, for it was hard to get to and I had just cut the ground wire when taking the old pump off for here at my age and condition my hands will not work in tight places.

Finally I decided, I going to take the bolt out where my old ground wires was hooked and move the new ground wire to there. With much frustration taking that old bolt out, moving my ground wire, I crawl out from under my blazer and go turn on the key, bingo, 62 #'s of fuel pressure, hit the starter, starts great.

I fail to understand why it did not get a good ground where I 1st hooked it up, yet one thing is clear, for some reason it did not. Sometimes we forget how important the ground wire is and just because it is tightly bolted to a portion of the frame does not mean its grounded good. I'm just glad I thought about it and did not pull the tank back off.

Thanks for posting back how it went.

Good job on getting the ground working good.

Yes ground is as important as the neg. wiring.
Grounds can be tested with a volt meter.
With a voltage drop test.

You may have had some rust or paint where you bolted it up !!!!!

When ever I bolt a ground to frame I always scrape off or grind off rust and paint around the bolt area.

Electrical plug going to the TPS has 3 pins. Looks something like this.

^ ^
^

Voltage between the top 2 measures, 1.5

Voltage between the one on the left & bottom one, 4.98

I might add in case this would make any difference, made a trip to town and just got home, I had the TPS unplugged so that I would not have a high idle.

Electrical plug going to the TPS has 3 pins. Looks something like this.

^ ^
^

Voltage between the top 2 measures, 1.5

Voltage between the one on the left & bottom one, 4.98

I might add in case this would make any difference, made a trip to town and just got home, I had the TPS unplugged so that I would not have a high idle.
You are a little high on sensor voltage to pcm
Black wire is ground.
One wire should be sensor reference voltage around 5 volts and should not change when you apply gas.

Now here is what you need to check!!!!!!
The wire or feed wire to pcm.
Specs are .32 volts to 1.28 at idle/close throttle.
With key on engine off open throttle slow and the sensor voltage to pcm should sweep even and steady from close throttle voltage .32 to 1.28 to 4.5 to 5 volts reference voltage with no drop outs or glitzes.
Even thow specs are up to 1.28 volts I would adjust it down to around .75 volts.

See if it does all of that.
And let us know.

Key ON engine OFF, TPS connector unplugged:
Grey wire to ground should be approximately 5 volts.
Black wire to ground should show less than 5 ohms resistance.

Key ON, engine OFF, TPS connector plugged in:
With throttle at idle, dark blue wire to ground should show approximately .5 volts or slightly less.
Slowly open the throttle and voltage should rise smoothly to approximately 5 volts.

Post your results.

LOL, MT beat me by 3 minutes!

Thanks.

I will check it again tomorrow and see what I get.

I happened to think about my Blazer this evening and I hooked the TPS back up and drove it over to the small town west of us where the wife and I eat on Tuesday nights. Perhaps that gave it some running time for the computer to get things set normal.

Anyway when we got back home it seemed to be idling about right.

I'm bumping this back up.

I had some exhaust leaks, should have replace muffler a couple of years back but kept putting it off. But getting 18 years out of the original exhaust does not sound bad at all. I recall buying a used Chevelle SS 396 in 1968. It had less than 5,000 miles when I bought it and less that a year the whole exhaust system was shot and Chevy replace the whole exhaust system free of charge.

I hoped replacing the exhaust might cure my blazer, and it did somewhat, for it does run quite a bit better. The idle is not quite as fast as it had been. The engine check light came on one time, during that time it run just a bit rough, yet the next time I drove it, it was off and running pretty good except for a higher than normal idle after it warms up.

I come across a scanner that will work on my Blazer and on our 2010 Toyota pickup with a somewhat reasonable price so I bought it, for I plan on driving this 92 Blazer for a few more years, so maybe it will come in useful on both of our rides. Plus maybe I can help out a friend sometime.

Its showing one code, DTC 45. 02 sensor rich.

From searching and reading I've learned this can come from at least 2 things, EGR valve & or Oxygen sensor. Back in 06 I had trouble with the EGR, I cleaned it once but them went ahead and replaced it with a new one and all was well. The original oxygen sensors are still in there.

I will not be messing with it till after the 1st of the week so I hoped to get some suggestion one what I might try.

I'm bumping this back up.

I had some exhaust leaks, should have replace muffler a couple of years back but kept putting it off. But getting 18 years out of the original exhaust does not sound bad at all. I recall buying a used Chevelle SS 396 in 1968. It had less than 5,000 miles when I bought it and less that a year the whole exhaust system was shot and Chevy replace the whole exhaust system free of charge.

I hoped replacing the exhaust might cure my blazer, and it did somewhat, for it does run quite a bit better. The idle is not quite as fast as it had been. The engine check light came on one time, during that time it run just a bit rough, yet the next time I drove it, it was off and running pretty good except for a higher than normal idle after it warms up.

I come across a scanner that will work on my Blazer and on our 2010 Toyota pickup with a somewhat reasonable price so I bought it, for I plan on driving this 92 Blazer for a few more years, so maybe it will come in useful on both of our rides. Plus maybe I can help out a friend sometime.

Its showing one code, DTC 45. 02 sensor rich.

From searching and reading I've learned this can come from at least 2 things, EGR valve & or Oxygen sensor. Back in 06 I had trouble with the EGR, I cleaned it once but them went ahead and replaced it with a new one and all was well. The original oxygen sensors are still in there.

I will not be messing with it till after the 1st of the week so I hoped to get some suggestion one what I might try.

Code 45 rich exhaust can be caused by a lot more than two things.
Here is 10 of them.

Fuel pressure,injector leakage,HEI Ign shelding,canister plurge valve.coolant sensor,map sensor,tps sensor,02 sensor contamination,Egr Valve stuck open and large vacumn leaks.
First thing to check.
If you have a scanner read out coolant tempt sensor and TPS voltage and Map sensor voltage for up to specs.
Post back voltage readings and tempt sensor reading on them.

Thanks much for all the post, after thinking about your last post, I remembered something.

Back when I suspected my spider injector was bad I got a friend to hook up his scanner to my Blazer, and after running the scanner he agreed that the spider was probably bad, plus I remembered this, he mentioned that coolant tempt sensor was not sending a signal. Saying it was probably one of two things, the sensor & or the connection at the sensor. I recalled him saying I've had to put new connectors on several of this type of sensors.

When ordering the fuel spider I bought a new coolant sensor as well and replaced both of them, I suppose thinking I cured both problems. Maybe I did not cure the latter, maybe the sensor was OK and it was the connection. With you mentioning it I will soon find out if its OK or not.

What kind of current flows back & forth through the sensor wire?

I've got a digital tester, but I know little about this except for testing AC & or DC voltage, that I've done many times.

And yes I bought a scanner. I understand it will work on my old Blazer and my 2010 Toyota. Plus one of our church members is having trouble with his service engine light coming on his 2007 Chevy pickup, maybe I can help him save a dollar or 2.

Thanks much for all the post, after thinking about your last post, I remembered something.

Back when I suspected my spider injector was bad I got a friend to hook up his scanner to my Blazer, and after running the scanner he agreed that the spider was probably bad, plus I remembered this, he mentioned that coolant tempt sensor was not sending a signal. Saying it was probably one of two things, the sensor & or the connection at the sensor. I recalled him saying I've had to put new connectors on several of this type of sensors.

When ordering the fuel spider I bought a new coolant sensor as well and replaced both of them, I suppose thinking I cured both problems. Maybe I did not cure the latter, maybe the sensor was OK and it was the connection. With you mentioning it I will soon find out if its OK or not.

What kind of current flows back & forth through the sensor wire?

I've got a digital tester, but I know little about this except for testing AC & or DC voltage, that I've done many times.

And yes I bought a scanner. I understand it will work on my old Blazer and my 2010 Toyota. Plus one of our church members is having trouble with his service engine light coming on his 2007 Chevy pickup, maybe I can help him save a dollar or 2.

Coolant and TPS sensors work off of low DC current voltage.
Tps sensor reading to computer is from .5 to about 4.5 volts.
Coolant sensor reading to computer is more ohm resistance.

But a good scanner will read out the tempt sensor reading in computer in degrees of tempt.
On the older modle cars and trucks tempt sensors wiring was a problem but the sensor and wiring was updated to a better setup.
Also Air intake tempt sensors are used on most systems.
AS to the injector voltage and control they have 12 volts dc to them and injector pulse is controled by a ground pulse signal from computer.
Which the scanner will read out.
Good Luck

This morning I checked these 2 thing out on my Blazer.

1st I drove my Blazer down the high way to get it warmed up, them I pulled the coolant sensor wire off, it has a Purple & yellow wire. This is the one at the front of the engine that's hard to get to.

I got these reading from them.

Purple to yellow 5.2 V

Purple to ground 20.1 MV

Yellow to ground 5.4 V

Would that prove that the sensor connection is OK?

Them I checked the TPS

Purple wire to white wire I get 5.2 V

Purple wire to ground has .5 V

When moving the Accelerator to open, it goes steady up to 3.12 V, not to the 5 V.

You need to have the key ON, engine OFF, and the sensors connected when checking voltage. It would be best to back probe them at the PCM to make sure the signal is going through the sensors and the PCM is receiving it.

Correct, that is with key on, engine off.

You mentioned you unplugged the connector.... it needs to be connected to the sensor when you check voltage.

The TPS connection was plugged in when I checked it, and it only reached 3.12 Volts when the throttle was wide open.

As MT said, TPS should be .5 volts at idle and close to 4.5 volts at WOT. Could be a faulty sensor, not mounted correctly to the throttle body, or out of adjustment.

Your voltage reading at the ECT sensor connector between the purple and yellow wire is correct which means both wires are good back to the PCM. It does not necessarily mean the connection at the ECT sensor is good. That can only be checked by disconnecting the PCM and measuring resistance between the purple and yellow pins in the PCM harness connector with the ECT sensor plugged in. The ECT sensor is a thermister, (a resistor that changes resistance as temperature changes). After the engine has been off for 8 hours, disconnect the ECT sensor electrical connector and measure the resistance between the two pins on the sensor. Then bring the engine to operating temperature and measure resistance between the two pins in the sensor again. Post both of your resistance readings along with the ambient temperature when you took the readings, and we can tell you if the sensor is responding correctly, and what the coolant temperature is.

EDIT

Check the manifold air temp sensor resistance readings the same way to compare with the ECT readings, they should show the same resistance. There are two wires on this sensor also, tan and black.

Thanks for the reply.

There is no adjustment that I know of for the TPS on a 92 S10 4.3 W engine, so I take it that the sensor is probably bad. Being as the Purple wire to white wire I has 5.2 V; purple to ground has .5 volts; them when throttle is open it will only go ot 3.12 volts.

It looks like this. (http://www.partsgeek.com/catalog/1992/chevrolet/s10_blazer/fuel_injection/throttle_position_sensor.html)

You can usually loosen the screws a bit and turn the sensor slightly, but I think you may have a faulty sensor or the throttle shaft is not positioned correctly in the TPS.

The PCM has two purple wires, one is the 2nd from one side, the other is the 7th from the same side. they are on different rows. So I measured resistance between the one yellow wire and both purple wires. This is with the wiring harness unhooked from the PCM & the ECT sensor wire hooked up.

These were taken with the engine fairly warm & the outside temp 56º

2nd purple wire, .295 to yellow wire

7th purple wire 4.24 to yellow wire

I'll take another reading in the morning with the engine cooled off.

I felt with the reading the TPS was bad too, I should have a new one when my wife's gets home from work tomorrow,

The three wires at the TPS are Black, grey and dark blue, probably some fading going on ;) Might want to double check and measure again ;) Let us know what range your ohm meter is on when you check the resistance.

Black wire goes to PCM connector "A" pin #11
Grey wire goes to PCM connector "C" pin #14
Dark blue wire goes to PCM connector "C" pin #13

The purple wire on the ECT sensor goes to PCM connector "D" pin #2
The yellow wire goes to PCM connector "C" pin #10
This link explains how the ECT sensor works: http://www.aa1car.com/library/coolant_sensors.htm

If you look very closely at the connectors, the pin numbers are there. Make sure you have the correct wire and pin.

I was on the ECT sensor leads that hooks to the computer, per what you said in post # 42 which is pasted below, not the TPS.

Seems you switched on me or I'm confused.

old master wrote:
"Your voltage reading at the ECT sensor connector between the purple and yellow wire is correct which means both wires are good back to the PCM. It does not necessarily mean the connection at the ECT sensor is good. That can only be checked by disconnecting the PCM and measuring resistance between the purple and yellow pins in the PCM harness connector with the ECT sensor plugged in. The ECT sensor is a thermister, (a resistor that changes resistance as temperature changes). After the engine has been off for 8 hours, disconnect the ECT sensor electrical connector and measure the resistance between the two pins on the sensor. Then bring the engine to operating temperature and measure resistance between the two pins in the sensor again. Post both of your resistance readings along with the ambient temperature when you took the readings, and we can tell you if the sensor is responding correctly, and what the coolant temperature is."



about 2 hours later outside temp is 53º

2nd purple wire to yellow wire reads: 1.406

Sorry, didn't mean to confuse, I just posted the TPS stuff because at one point you were looking at a possible problem with it.

1.406 hmmm are you sure the meter was on the ohms scale?

At 53 degrees Farenheit, the resistance across the two pins in the ECT sensor should be around 5600 ohms. Remember to unplug the sensor and touch the probes directly to the pins. To check it at the PCM, unplug the PCM, connect the ECT sensor, and touch the probes directly to the pins in the PCM harness connector. Both ways should be very close in resistance.

This link will show the resistance values at various temps, both Centigrade and Farenheit.
http://www.explorerforum.com/photopost/showphoto.php?photo=30138&size=big&ppuser=42004

That's OK. I may not be explain what I do all that good.

Maybe I got a bit confused, this is much for me, give me one without a computer, & I would feel at home, yet maybe I'm getting just a bit of a grip on trouble shooting this thing with a computer. Yet it makes me long for my cars of yesterday, for I was at home with them when opening the hood when you had the simple firing system along with a carburetor such as the Rochester 4 Barrel Quadrajet & I would feel at home

I can't help but think of a long time mechanic at the local Chevy house that has many fans, they love for him to do the work on their cars. Yet, when the computers came in, he did not take to them good at all. Of course he is older than my 64 years, probably now at about 75, while still working about 2 to 3 days per week. He does not get involved in the computer games. I might say, he can still tear an engine down and put it back together & or a brake job better than most younger mechanics & he is still strong as an ox. He is one reason they have many repeating customers throughout the years. I might add the younger mechanics looks up to him & goes to him for advise on his days at work.

During this ordeal I can appreciate him and his dislike of computerized cars & why he does not care to tackle them. Anyway, I just want to say thanks for your help & patients.

All of these reading came from the lead unhooked from the computer under the dash, with the leads hooked up to the sensors at the engine.

I'm using this multimeter (http://www.iequus.com/Product/Detail/B42B093D-9BF5-4EF4-AA36-77374C6F2293) set to the 3 selection to the right of off to check the resistance. If wrong please let me know.

Resistance on TPS leads to computer, with leads unhooked from computer: with leads connected to TPS.

Black to gray - 2.91
Dk Blue to gray - 2.41
DK blue to Black - 1.237

Resistance, ECT sensor lead, purple to yellow, at computer now shows 2.89

Something isn't right, either the sensor or the tester is screwy.

Set the tester to OHMS, (right where you had it). Touch both probes of the tester together, should read zero ohms. If it does, unplug the ECT sensor and check the resistance between the two pins in the sensor and post your results. If the tester doesn't show zero when you touch the probes together, the tester is not reading correctly...time for a new one.

I got my TPS sensor, installed it. I've driven it 2 times. Last night I drove probably about 35 miles, all went well, no high idles, it run great. Today I drove it about 18 miles and when I pulled into my driveway it was idling very fast. I left it running and got out, raised the hood, pulled the connector off the TPS and it idled down a bit. The engine seems to be running pretty smooth, no missing at all, if not for the high idle at times all would be well.

Having had the computer disconnected the code is gone, and so far it had not produced another one. If its going to throw a code wonder how long it might take?

I ordered a manual hopefully with the breakdown it gives I will I will comprehend all of this a bit better.

The cable from the cruise control to the throttle was causing my throttle to hang. It seems to be OK, yet when its hooked up, the throttle will hang when the TPS is reading about 3.38, unhooked, it goes to over 4.5 smooth as silk.

A person might not notice it hanging with the breather hooked up, or unless they're checking voltage on the TPS. Of course if you going down the highway and floor the gas pedal you'll notice it.

Still have not got the high idle conquered, with the weather getting a bit better, & the days getting a bit longer I will call a friend & see if we can set a time that he can hook up his computer. He works for a out of town Chevy house, during this time of year its dark by the time he gets home. When problem is found I'll let y'all know.