89 Blazer Wouldn't Start Now Running Rich

I ran the engine O2 sensor disconnected and pulled the pcv valve tube at the inlet manifold - to give a big vacuum leak - the O2 sensor voltage went up from 700mV to about 720mV as measured on my dvm - strange - it should have weakend the mixture and the voltage gone down but maybe with so much unburnt fuel it helped a bit more fuel burn??

Coolant temp around 170F.

Going to reconnect O2 sensor and see if ecm will enter closed loop mode OK


Mark

You need to get the engine tempture up to 195F.
If the 02 is acting strange go for another one.
In looking over your post I did not see where you have checked your base timing.
Have you checked that yet like disconnecting the set timing connecter and reading base time?
Also if running rich check the injector spray or for flooding and leaking there.
What is the map sensor readings at idle and under load?
Also you might want to drop the exaust pipe and see what it does.
If it has been running rich for a long time the cat may be stopped up.
Also get a vacume gauge on it and give us the vacume readings.
MT

This engine runs a bit cool I think - the last owner fitted an oil cooler for towing - what is the lowest temp that I can run at? Will this prevent the ecm from entering closed loop mode?

I haven't checked the timing yet - still haven't found the wire to disconnect -I will seek it out and get an inductive strobe lamp. I doubt if this is the problem but I am running out of options fast LOL

I wil get MAP sensor reading but it seems to be OK - around 5.0v with engine not running and I have seen values of around 1V but I will get some real data. It doesn't idle too well. I have to keep reving it but I could get reading when it is cold and the rich running isn't so bad. The manual suggests disconnecting the MAP sensor and allowing the ecm to use the fixed value - I tried this and the engine still ran rich.

The 2 injector spray patterns look good and if I remove injector electrical connections and crank the engine the injectors don't leak. Fuel pressure is good at 11 to 12 psi

I had a Cavalier with a stopped up cat but i am getting a good exhaust gas flow on this one so far.

I will see if I can find a vacuum gauge but I think that the engine is OK mechanically. One moment I was driving fine and 20 minutes later it wouldn't start. I had it towed home.

I really appreciate your help with this one. I haven't been able to get at the ecm - it is buried behind the glove box

Mark

This engine runs a bit cool I think - the last owner fitted an oil cooler for towing - what is the lowest temp that I can run at? Will this prevent the ecm from entering closed loop mode?

I haven't checked the timing yet - still haven't found the wire to disconnect -I will seek it out and get an inductive strobe lamp. I doubt if this is the problem but I am running out of options fast LOL

I wil get MAP sensor reading but it seems to be OK - around 5.0v with engine not running and I have seen values of around 1V but I will get some real data. It doesn't idle too well. I have to keep reving it but I could get reading when it is cold and the rich running isn't so bad. The manual suggests disconnecting the MAP sensor and allowing the ecm to use the fixed value - I tried this and the engine still ran rich.

The 2 injector spray patterns look good and if I remove injector electrical connections and crank the engine the injectors don't leak. Fuel pressure is good at 11 to 12 psi

I had a Cavalier with a stopped up cat but i am getting a good exhaust gas flow on this one so far.

I will see if I can find a vacuum gauge but I think that the engine is OK mechanically. One moment I was driving fine and 20 minutes later it wouldn't start. I had it towed home.

I really appreciate your help with this one. I haven't been able to get at the ecm - it is buried behind the glove box

Mark

Check and set the timing first thing.
A vacume gauge will show late timing/low vacume readings /cat stoped up. if timing is the problem.
You need to get a thermostat that will bring the engine tempture up to 195F for them pcm to go into colsed loop and start adjusting the fuel mixture.
Work on them 3 things and you may fix the problem.
MT

I found the timing wire and opened it . I started the engine -I think that it was very retarded - it ran very badly - seemed to be msssing - I had my foot to the floor and it was running at 1500 rpm or so. I couldn't get it to rev very high at all. Seemed to get very hot there one backfire and flame out of the carb


I replaced the timing wire and restarted. I am seeing the ecm in Clear Flood mode. The O2 sensor is reading around 650mV as expected.

I checked the MAP sensor - the engine won't idle very well as it is flooding at idle but I see a MAP voltage of around 2.00V at idle - it goes lower maybe a bit less than 1 volt when I have to blip the throttle to keep the engine from stalling.

The max coolant temp is 170F - it was higher after sitting but soon came down to 170. The scan tool is reporting Closed loop status from the ecm, so I think that we are entering closed loop mode OK even with a cool running thermostat




Could the IAC be doing this - I am fast running out of ideas

thanks Mark

I found the timing wire and opened it . I started the engine -I think that it was very retarded - it ran very badly - seemed to be msssing - I had my foot to the floor and it was running at 1500 rpm or so. I couldn't get it to rev very high at all. Seemed to get very hot there one backfire and flame out of the carb


I replaced the timing wire and restarted. I am seeing the ecm in Clear Flood mode. The O2 sensor is reading around 650mV as expected.

I checked the MAP sensor - the engine won't idle very well as it is flooding at idle but I see a MAP voltage of around 2.00V at idle - it goes lower maybe a bit less than 1 volt when I have to blip the throttle to keep the engine from stalling.

The max coolant temp is 170F - it was higher after sitting but soon came down to 170. The scan tool is reporting Closed loop status from the ecm, so I think that we are entering closed loop mode OK even with a cool running thermostat




Could the IAC be doing this - I am fast running out of ideas

thanks Mark

Well first things first.
Did you set the base timing?
MT

I will get a strobe on it tomorrow - I hope that it will run long enough with the timing wire disconnected but I will give it a try. I was suprised how badly it ran with the timing wire disconnected. I am not sure what could have changed the timing. The distributor is tight and shows no mechanical play but I will check it. I think that I have the correct wire - it is the tan and black wire behind the carpet in the passengers footwell.

I believe that cylinder #1 is at the front on the side where the steering colum comes down to the steering box.

Mark

You have found the sore spot for sure.
You should have checked that to start with.
I think BlazeLT asked about that 50 post ago.
Your timing is way real slow. And get a 195F stat in it.
2 volts on map sensor is low vacume that is usually caused by slow timing.
Turn the dist counter clock wise some and see if it starts running better and see if vacume comes up and map sensor voltage goes down to 1.0 -1.5 volts.
Then get a timing light and get that base timing set with the timing wire unpluged.
And yes no 1 cylinder is on front drivers side.
let us know how it goes.
MT

No-one touches timing anymore LOL. Not like the old days when I would strobe my car every 6000 miles after a points change. I recently strobed my 1972 Triumph Boneville but then hand tweaked it for performance.

I am still suprised that it has changed when nothing is loose but stranger things have happened. The manual says that this engine is timed at 0 deg BTDC with the timing wire open circuited. I have found the timing mark but I will have to clean it a bit to be able to read it and see which line is the 0 deg mark. I suppose I could use a pencil in the plug hole and check for tdc that way. I think that I may do that to double check the timing marks.

The map sensor will go down to around 1 volt but the engine stalls then as it floods.

I am still not convinced but I will report back tomorrow and let you know what I have found. Getting the O2 connector back on was not a fun job!


Mark

Here something interesting. When I was replacing the ignition module in the distributor last week I noticed that a section of pickup stator metal core had fractured off and was hanging down and only kept in place by the ignition module. I am wondering now how this would effect the spark triggering pulses in the stator coil. Maybe this is why the engine rp, data on the scan coil is jittery. I suppose that this distributor should be replaced. I found a site on the web that had them for around $250. I haven't checked NAPA but Advance Autos had one for $98 - I have been stung with cheap parts there before. Where would you advise getting a replacement distribitor if it turns out that I need one.

I got an inductive strobe this morning and hope to strobe the engine later.

Mark

Since you aready have smoke(fog) , just add some music and crank it up and enjoy your rolling disco . HAHA .
If that stator that you found is magnetic . It would drastically change its properties if a star point was broken off . The strength of the magnet would be reduced on the exact opposite side too . Leaving a third of your ignition system unbalalanced . Going on vacation for spring break tomorrow .I will catch up on your progress after Easter. hope you git-r-done soon . Rob

Thanks Rob,

Actaully it's more of a smutty disco with a big black sooty patch on the garage floor where the exhaust blows LOL - it doesn't smell to good either.

Have a good vacation. I am between jobs right now so that is why I am working on this vehicle slowly and not trying to throw money at it. I power washed the deck and fitted a fender radio on my farm tractor yesterday - got tired of Blazering for one day.

The rotor is the magnetic part. The stator is the pickup coil but with a chunk of the core broken off I am sure that the sensitivity will be way down and may lead to fasle triggering or other strannge effects. I was presuming that it had been like it for a long time but it may have just broken off and be the cause of the problem. More testing is required with the strobe light which I bought yesterday. Long term I don't want it like this because the broken part of the core could easily chaffe through one of the pickup coil output wires, since it is along side the point where the output wires exit the stator coil.


Mark

I just put a timing light on the Blazer and with the EST connected the crankshaft timing mark is jumping all over the place - anything from TDC to around (estimating) at least 30 to 40 degrees of advance. This is a new strobe unit but I think that it working OK and the inductive pickup coil is well away from the other leads. So I doubt if the strobe is mistriggering. This might tie in with the engine rpm reading on the scan tool jumping around too. I tried running the strobe powered from a clean lab 12VDC supply and the mark is still jumping all over the place. I unpluged the EST timing lead (tan and black) and the timing mark wasn't even visible - it is very very retarded by the sound of it.

I am going to change the distributor since the large piece of the stator pickup coil metal core that I found broken off is probably having a big effect on the output voltage produced by the rotor magnets. The distributor needs changing anyway since it is broken and I don't want to drive it like that. Hopefully it is actually the root of the problem.

I think that the NAPA distributor is a good bet and I may transfer the new Delco ignition module that I bought to it.

Is there any point getting one of these

http://performance.drivewire.com/getparts/index.aspx?pref=Distributor|CHEVROLET|S10%20BLAZER |1988||V6|4.3|262|TBI|Ignition%20System

or will the NAPA part work just fine.

Now to my main question. I will set the engine to No 1 TDC firing stroke (the rotor will be pointing to the plug lead that goes to No1 cylinder) before removing the old distributor. I am used to seeing points opening. This has always allowed me to get the timing pretty close before starting the engine and then I can easily strobe the timing in. However with a distributor which has rotating magnets and a pick up coil will I be able to tell visually the point at which the rotating magent is about to produce a spark ie akin to the point at which the points would be just opening?

thanks Mark

Tonight was a red led letter day. My Blazer finally left the garage and drove under it's own steam. It is very smooth on the new and final set of plugs that I fitted yesterday.

I have fitted a new distributor and now the timing marks are rock solid under the strobe light. The rotor and stator on the old distributor were fouling each other and the stator core was damaged.

I had a devil of a job getting the new distributor to locate into the block all the way. I could pick up on the camshaft worm gear but the distributor would not go the last 1/4 inch or so. It was bottoming on something. It would go in with the rotor arm in the wrong position but not with the rotor arm in the correct alignment position. I played around with it for a couple of hours. Unfortunately due to my own fault I tore the distributor base gasket but decided to carry on and then suddenly the distributor was in all the way. At this stage I didn't want to pull it back out so I went ahead and fitted the cap and leads and timed up the engine. I have bought a new gasket but it is not fitted. What is the likely hood that oil will weep up around the distributor body without this gasket. I hate to pull it again but I will if I have to.

MT picked up on my cool running thermostat. I talked with the last owner and he fitted a 170 degree thermostat becuase he didn't like the engine running hot on his interstate cruises. It does get pretty hot here in North Carolina. What are the implications if I leave the 170 degree thermostat in or should I really change it to a 195 degree one?

Thanks for everyones help with this one - it has certainly been an education to me.

Mark

Tonight was a red led letter day. My Blazer finally left the garage and drove under it's own steam. It is very smooth on the new and final set of plugs that I fitted yesterday.

I have fitted a new distributor and now the timing marks are rock solid under the strobe light. The rotor and stator on the old distributor were fouling each other and the stator core was damaged.

I had a devil of a job getting the new distributor to locate into the block all the way. I could pick up on the camshaft worm gear but the distributor would not go the last 1/4 inch or so. It was bottoming on something. It would go in with the rotor arm in the wrong position but not with the rotor arm in the correct alignment position. I played around with it for a couple of hours. Unfortunately due to my own fault I tore the distributor base gasket but decided to carry on and then suddenly the distributor was in all the way. At this stage I didn't want to pull it back out so I went ahead and fitted the cap and leads and timed up the engine. I have bought a new gasket but it is not fitted. What is the likely hood that oil will weep up around the distributor body without this gasket. I hate to pull it again but I will if I have to.

MT picked up on my cool running thermostat. I talked with the last owner and he fitted a 170 degree thermostat becuase he didn't like the engine running hot on his interstate cruises. It does get pretty hot here in North Carolina. What are the implications if I leave the 170 degree thermostat in or should I really change it to a 195 degree one?

Thanks for everyones help with this one - it has certainly been an education to me.

Mark

It may leak. You might raise it up just a hair and get a little silcone sealer in there.
On the thermostat your engine will not run much cooler with a 170 than a 195
stat and on a good warm day it may not even run any cooler.
But it can cause your engine to run richer and prevent the computer system from working right or controlling the fuel mixture rich
Also your engine need to run at 195 degrees to burn the condensation out and keep the oil from sludging up.
MT

I think the reason the distributor would not drop down that final 1/4" was because of the oil pump drive coupler that engages the bottom of the distributor shaft . It is similair to a flat blade screw driver with a nylon collar around it .
Fortunately the gasket is not under pressure , so if your pcv valve is functioning correctly , you may only see a small amount of seapage .
I was playing with my timing this week trying to get the best low end torque .
I am thinking about changing to an MSD ignition box . Rob

Thank you for your replies. I will take a look at the thermostat

Regarding aligning the distributor, the oil pump does sound like it could be the problem I wonder if it is necessary to use a screwdriver to adjust the position of the oil pump slot so that the distributor can be pushed all the way home.

I will take the Blazer for a 50 mile interstate drive and see if there is any oil leaking around the distributor. This engine is pretty leaky anyway - it is an original engine with 260,000 miles - not bad eh. The crankshaft rear oil seal is a bit leaky now but it keeps on going.

How did your igniton timing experiments go? I used to advance my English engines to get more top end power at the expense of low end torque.


Mark

My timing tinkering seems to have worked out well . My ultimate goal was to keep the engine from running hotter than normal on road trips . Since I am not using factory original equiptment with lots of sensors removed , the computer controled timing does not seem reliable . I think I found its sweet spot . It cranks very easy, The temp stayed the same while pulling my trailer with ATV , and it had tire ripping torque off the line . Previously , even through the winter months , the temp would get up around 220 . I have a 160 thermostat and back up guages . Now it stays around 180 . The timing is the only thing I changed . Rob

What sort of distributor do you have and how is the advance and retard taken care of. Mine is done by the computer and knock sensor. In the old days it was done by springs, weights and a vacuum diaphram.

I have an electronic ignition module on my Triumph Boneville that has a built in advance curve basesd on engine rpm.

Did you advance or retard your base timing?


Mark

Hi Rob,

I looked at your post more closely and I imagine that you are running the stock distributor, ECM and EST module which is attached to the firewall.

Have you put a strobe on the engine and seen what sort of ignition advance you are getting at different engine rpm's. I could compare them to what I am seeing if that would help.

Sounds like your rtming was off a bit and causing the hot running. Be careful that it isn't too far out as it could casue a burnt out valve or holed piston. Well that is what used to happen in the old days. The fact that your engine is now running cooler is a good sign.


Mark

Since I converted to carb , My throttle position sensor is not connected so the computer doesn't know it is revving up . I know what the knock sensor is supposed to look like and where but I can't find it . I did not have any luck with factory base timing . When running the strobe on it , I noticed that when I rev it the timing retards briefly before advancing , since all the parts are still connected to the stock ignition parts as you mentioned ,I basically have it set by ear and seat of the pants . Its really impressive to light up these big tires without braking it down first but I still hear a brief moment of spark knock when it shifts gears under heavy thottle . I am looking at doing away with the stock computer completely with an MSD igition system. Rob

There are two connectors on the distributor. One goes to the coil and the other sends rpm information to the ecm. I don't know if the ecm needs to use the tps at all.

I will take a look at my manual and see if I can find out where the knock sensor is located

The MSD system sounds interesting. I will have to take a look at it on the web.


Mark

My manual (haynes ) says to tap on the exhaust manifold at a certain place and listen for the rpm to change . Nothing happened , I searched the entire engine block . I think it was removed before I got it .I have a couple of wires with no ends attached. Anyway, I am happy with the way it is working right now , except at the pump . My carb is calibrated for performance but I am going to re-jet it for economy per Edelbrocks instructions .How did yours do on its first week back on the road ? Rob
P.S. Lets go to private messages so the mod won't fuss .

Here's a picture of my old damaged distributor. The metal coil former to the right of the white wire is fractured and hanging down. It is resting on top of the ignition module

http://img95.imageshack.us/img95/9739/dscn30399aa.th.jpg (http://img95.imageshack.us/my.php?image=dscn30399aa.jpg)