92 hard to start when hot

[old_master]

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!

[Jerry80871852]

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.

[Jerry80871852]

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.

[MT-2500]

Originally Posted by Jerry80871852

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.

[Jerry80871852]

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.

[MT-2500]

Originally Posted by Jerry80871852

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

[Jerry80871852]

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.

[old_master]

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.

[Jerry80871852]

Correct, that is with key on, engine off.

[old_master]

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

[Jerry80871852]

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

[old_master]

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.

[Jerry80871852]

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.

[old_master]

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.

[Jerry80871852]

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,