95 S 10 ZR2 engine dies while driving....

....then restarts.

I have a '95 ZR 2 pickup that I purchased as a bit of a basket case. No need going into details other than what the problem is that I am having now.

The original problem with the truck was that above 2K rpms, the engine would stumble/run rough/no power/act as if it had random misfires. If you WOT it, it would eventually get up and go over 3K and smooth but once you went back to around 2K to 2.2K it would do as I said. Below 2K it would run alright but at idle it had a bit of a rough miss. Every now and then, a code would be set. First it started out as a TPS low or open code. I changed out the TPS and it was okay for about 10 miles and then it acted up again. Engine light came on. This time, the TPS was set again along with a MAP sensor low reading code. I ignored the MAP sensor code since when it stumbles etc I assumed that the ECM was interpreting it correctly since there would be a loss of intake vacuum so I went back to the TPS. Looking at the plug, I determined that the pin looked worn and weak so I replaced the pin connectors inside the plug and replaced the weather packing. Same problem came back. Time to bring out the artillery.

I borrowed the Snap-On Modis from work and drove with it hooked up (my data logger wouldn't work on this truck for some reason) and when the truck did it I pulled over and looked at the Freeze frame.....nothing. The TPS code came back. I then traced out the wires from the TPS to the ECM and performed a wiggle test and nothing. I let the truck sit for a while...like two weeks.

I then started running it again and it did fine for about a week and then it started again. This time I got a P0303 (misfire cylinder 3), MAP low signal or open. I was becoming frustrated. I pulled cylinder 3 plug and checked, it was coked up a bit but that is another problem I won't go into at this time. After cleaning the plug and putting it back in the miss was gone. I drove the truck and again, at 2K to 2.2K it began it's stumble etc. The engine light came on and the code was for intermittent signal to coil pack 1 and 4 ..... WHAT?!?!? ... there is no coil pack on this engine! I then looked over the schematic .... again ( I looked it over when I was doing the TPS prior) and it didn't match. I then looked at a '96 which did match as far as the ignition circuit was concerned (Snap-On Shop Key manual). I determined that the ESC module might be at fault since it appeared to not have any output to the ECM so I changed it out. There was none available for the '95 but there was for the '96 ... and it was cheaper. I bought the '96 and ran the truck and it was fine for the first 10 miles and it did it all again. The engine light came on and the code was for a faulty signal from coil pack 1/4. Again ..... what coil pack? So, being around from the time there were points in a car/truck I decided that the coil might be breaking down under load. I swapped out the coil and the truck was fine. I even went on a 300 mile trip with only one problem and that was an O2 code but that is probably due to needing a new exhaust.

And now my problem.

The truck runs great, when it does, idles smooth and accelerates fine and plenty of power except there is one problem. You can be driving along and the engine quits running. The torque converter stays locked up (above 40) and all gauges are reading as long as you don't put it in neutral or hit the brakes. After pulling over the truck would restart as if there was never a problem. I have done wiggle tests when it is cold, I have done wiggle tests when it is hot. The other night, it was so bad that I would drive about 1/4 to 1/2 mile and it would do it and then it wouldn't restart. After about 3 to 5 minutes it would start as if nothing was wrong. Finally, it did it again and I was doing 40 and I was in a bad place and just kept going in a coast, engine was still turning over, had oil pressure, RPM was 1800 and power steering and it also backfired once. After it hit about 15 mph it went to 0 rpm and I was able to pull over safely. It wouldn't start. It cranked as if it wanted to but it wouldn't start. I went out and wiggled wires but to no avail. Finally after about 5 to 10 minutes it started and I was able to drive the 4 miles home without incident.

I decided to drive to work the next day and it did it once on the way which is a 20+ mile one way commute. I thought about it and decided I was going to put the original ESC module back in with the thought that there was a difference in '95 vs the '96. (I know, it drove for about 400 miles with no problems but what the heck) The truck ran fine on the way home. The next day it ran fine to work and it ran fine until I got home to my lane which is a quarter mile long and it died and I coasted to a stop. It immediately restarted.

I remember reading in here a long time ago that in that vintage S 10 there were ignition wire problems with a pink wire on the ignition switch that would cause the vehicle to just quit running and it was intermittent. Also, I am wondering if the coil could be bad since it appears that it did backfire and there is the smell of gas which to me indicates the CPI is still firing for the ECM still thinks the engine is running. This leads me to believe that it is an ignition problem that is removed from the ECM.

This is the 5th S 10 I have owned but this is the first time I have hit a wall. This truck appears to have been spawned in the darkest recesses of he11 or someone died in it and it is haunted. The codes cannot be read with a code reader, either Snap-On or Acton or OTC. A MODIS or a TECH II is needed or some other scanner that can see through. I have a data logger that will not work even though there is an OBDII plug.

Any ideas, I am all ears.

Thanks, Mikado

check fuel issues. either a bad pump or you are leaking fuel and flooding it.

You need to pin down when it dies and won't immediately start whether you have spark, fuel pressure and injector pulse. The 95 is not a full obd11 system it is a transition year and basic scanners will not work.

Drove around with a Snap-On fuel gauge tie wrapped on the windshield wiper arm. Pressure at KOEO was 64. KOER varied from 58 to 63 depending upon accelerator (i.e. whether fuel regulator was closed or open or somewhere in between)

I should have mentioned that there was a smell of gas the time it backfired and I pulled over. Almost reminded me of when carbs used to flood out.

Thanks for your response.

Mikado

You need to pin down when it dies and won't immediately start whether you have spark, fuel pressure and injector pulse. The 95 is not a full obd11 system it is a transition year and basic scanners will not work.

AS I mentioned, I drove around with the MODIS and there were no codes either set or pending. The freeze frame data showed everything normal including the pulse width on the Injector.

When I tried to measure spark, I had it at the coil and when I plugged it in the truck started.

That is the problem, when you attempt to diagnose this, you are either along the road and then it immediately starts ups upon a crank or I was in the dark.

This is really a beeottch. It never does it at the shop, can't seem to induce it.

Thanks,

Mikado

Well, it finally crapped out the other day and wouldn't restart on the first two or three tries. I have been carrying some tools just for this.

Fuel pump pressure at the schraeder was within specs.

I then took one of those rewindable jumper wires and clipped it to the coil post and brought it inside the cab so that I could see if there was spark......no spark.

I then would move the harness in different spots, first on the passenger side in the vicinity of the coil...no luck. I then did in back of the engine around the distributor...no luck. When I went to the drivers side where the harness divides with one part going up over the brake booster and the other going down the side of the manifold and moved it in a downward motion...the engine started.

Looks like it is in the harness. Just changed out a 4.3 into a '95 Blazer at work and the salvage engine came with a complete harness.....guess who laid a claim to that harness?

I will swap out this weekend and I am going to inspect the old harness. I am curious as to what it could be since it continues to inject fuel. I am suspecting the lead wire to the ESC mod or the coil. I thought about doing an overlay to the hot on the coil prior to swapping out the harness to verify a power situation. I might do that first.

I will update as I go.

Mikado

intermittents are a hassel. especially when the ignition is the cause.

1994 S10 4.3L vinZ TBI engine. my problem was very intermitttent missfires. then it would stall and act like it was flooded at any speed. restart ok but not great.

removed the ICM had it tested[autozone] . it was defective . no more missfires and much faster cold starts.

then the stalling for no reason , this turned out to be the oil pressure switch . also this switch / sender gave a low oil pressure reading. the new component now gives the correct oil pressures and no stalling intermittently.

intermittents are a hassel. especially when the ignition is the cause.

1994 S10 4.3L vinZ TBI engine. my problem was very intermitttent missfires. then it would stall and act like it was flooded at any speed. restart ok but not great.

removed the ICM had it tested[autozone] . it was defective . no more missfires and much faster cold starts.

then the stalling for no reason , this turned out to be the oil pressure switch . also this switch / sender gave a low oil pressure reading. the new component now gives the correct oil pressures and no stalling intermittently.

I agree j cat, intermittents, when they come into the shop, usually have an exorcism performed prior to troubleshooting...<g>.

I took my module into Advance and it wouldn't test on their tester for some reason. I think the "kid" didn't know how to use it. I took the plunge and bought one anyway but no luck, it didn't cure the problem.

One thing I dislike the most is to "throw" parts at something, not fair to the customer and not fair to my wallet when it is my own.

Sometimes, the best thing to do is to walk away and let the subconcious think about it but tough to do when your service manager is screaming at you...well, maybe not screaming but sure as heck not giving you any peace.

Thanks for the support,

Mikado

autozone has the tester. made by WELLS.

when these vehicles get old some components like Spark plugs and wires/O2 sensors /ECT/ICM these components loose the ability to properly function. 10years old and over 100,ooomi best to replace than wait for failure.

also the ICM made back then has issues. circuit runs are too thin to handle the current flow which results in a weaker spark. also the timing control is faster .