Envoy Stalled At Stop Light - 3rd Incidence in 1 year.

[gmcman]

Would like to rule out excessive fuel when cold, couple that with low compression could present a difficult combustion sequence. One would point to leaky injectors until the PCM went into closed loop to compensate.

I can't think of much on this end other than confirming a compression issue. You could pull plugs from 2,3&4 since they are easy and after it sat overnight run a dry test. Then add a few drops of oil to the cylinders and perform a wet test and compare the results.

I would wait to check the crank sensor to avoid a CASE relearn, and from what you stated this is only a cold running issue or primarily a cold issue?

Generally when the idle drops the TB should open more, but if you have a difficult time igniting the mix then there's another issue for sure. Plugs can be picky after they have been fuel fouled so if that's the case it's something to consider...I would check the condition of the plugs to make sure they are not fouled.

 

[CaptainXL]

I will check the compression again. Last time I checked it was about 170 wet. My compression could be considered low when doing dry or wet testing but probably rings load up and cure whatever problem when running? Hard to say.

But (big BUT!) Fuel trims are spot on close to 0. No major combustion or fuel delivery issues that I can see. This seems to contradict any compression issues. So I am not trusting my compression gauge.

You know me...I have checked just about everything possible and done all the recommended maintenance including spark plugs and checking coils.

It's just baffling... The only times it has happened is in low rpm maneuvering around parking lots or putting my trailer onto it's spot. And also like today about a minute after starting the truck in park. In all cases the engine just shuts off as if I turned it off my self and took the key out. Let me see... I will take the column cover off again and see if wiggling the harness makes any difference. Maybe I got a bad ignition switch. Just replaced it last year (Borg Warner). Thanks gmcman.

 

[kickass audio]

I had this issue happen with my envoy about a year ago. Except it made no difference whether it was cold or hot, it would just die at random while at idle. One time it tried to die while I was driving but it caught itself before it completely died out. I only had this problem happen once since that point in time but I think it was my fault because I dont think my key was all the way in position.

Anyway its hard to say what caused the issue on mine as I had a LOT of things fixed at that time. I had a new throttle body installed, I had a clogged catalytic converter, filthy fuel filter, OEM plugs at 100k (they are supposed to handle that but mine were on the dirty side) a bad secondary air pump (the shop called it a smog pump) and a half stuck EGR. I had them replace the throttle body, run some catalytic converter cleaner and it cleaned it up like a brand new one, put a new fuel filter in since I don't think it was ever changed, replace the spark plugs with Champion Iridium (lots of members on here discourage getting plugs that are not AC delco but I have had 0 issues with my champions), replaced the secondary air pump and then replace the EGR valve. They had to keep the truck for a week though because I also had them upgrade the software on the entire truck's computer system for the BCM, PCM and another component of the truck as it was never updated since it left the factory. With those upgrades the PCM had to relearn the throttle body to keep it at the right position for idle and it took a lot of drive cycles to get it to learn. When I picked up my truck at the end of the week it was still not done learning so I had to drive it for 2 more days and it finally finished learning. During that learn process my truck would buck at stops on the occasion and stall out. After it learned it had 0 problems.

You don't by chance have any power issues where your battery dies on you at all to reset the PCM do you?

 

[gmcman]

Ign switches could surely cause a wacky scenario....170 wet is pretty low. Only true test is a back to back dry/wet comparison. I don't think the compression will affect the fuel trims enough to cause a stall, especially if you are near zero. That doesn't rule out stalling if compression is too low.

 

[gmcman]

a bad secondary air pump (the shop called it a smog pump) and a half stuck EGR.

replaced the secondary air pump and then replace the EGR valve.

Was this on the older Envoy, with the 4.3 V6? Reason I ask is the 4200 does not incorporate an EGR valve.

 

[gmcman]

In all cases the engine just shuts off as if I turned it off my self and took the key out.

That's definitely odd, hopefully it leads to an ignition switch or something electrical and not compression related.

 

[CaptainXL]

That doesn't rule out stalling if compression is too low.

Understood. But to me that doesn't make any sense. I would think that if compression really was a major contributor to the issue then the engine would stall more often and run rough. It does neither. Poor compression means air/oxygen is leaking past the rings. If that was the case there would be incomplete combustion (rich) and fuel trims would definitely be OFF. Definitely. So none of the old standby explanations are making any sense. I need to look elsewhere.

You don't by chance have any power issues where your battery dies on you at all to reset the PCM do you?

No. The truck starts up just fine all the time.

 

[gmcman]

Understood. But I would think that if compression really was a major contributor to the issue then the engine would stall more often and run rough. It does neither.

But it does this when cold and under load at low speed. I agree it's rather excessive behavior for fuel fouled plugs and low compression but something to check if we can't narrow it down.

 

[kickass audio]

Was this on the older Envoy, with the 4.3 V6? Reason I ask is the 4200 does not incorporate an EGR valve.

I have the 4.3 i6 not v6. It is an 2004. It has the egr where its on the passenger side of the engine towards the top right next to the transmission dipstick. It looks like its called an air check valve. 2004 GMC Envoy Air Check Valve - Dorman 911-003 | StockWiseAuto

The pump that was replaced is Air Pump - A1 Cardone 32-2402M | StockWiseAuto

Not the same ones I had installed but the exact same part itself.

 

[CaptainXL]

But it does this when cold and under load at low speed.

It will stall when the engine is hot as well like when parking my trailer at a state park after getting off the highway. Or when getting of the main street to park at Sam's club. These are both fully hot engine scenarios.

Man...if I just had one more bit of evidence. Like if it only happened when turning the steering wheel or something. Let me think about it... Got to do one of those Einstein thought experiments.

 

[gmcman]

I have the 4.3 i6 not v6. It is an 2004. It has the egr where its on the passenger side of the engine towards the top right next to the transmission dipstick. It looks like its called an air check valve. 2004 GMC Envoy Air Check Valve - Dorman 911-003 | StockWiseAuto

The pump that was replaced is Air Pump - A1 Cardone 32-2402M | StockWiseAuto

Not the same ones I had installed but the exact same part itself.

We need to set the record straight... The 2002-2009 Envoy with the 6 cylinder is a 4.2 I6, not a V6. The 4.3 is the V6. There is no EGR valve, but you seem to have the air injection pump.

 

[gmcman]

It will stall when the engine is hot as well like when parking my trailer at a state park after getting off the highway. Or when getting of the main street to park at Sam's club. These are both fully hot engine scenarios.

Man...if I just had one more bit of evidence. Like if it only happened when turning the steering wheel or something. Let me think about it... Got to do one of those Einstein thought experiments.

Without driving around with a Tech 2 this is going to be difficult.

When this thing purrs along the highway, all day, it runs like a top correct? I keep going back to injectors loading up the cylinders just enough to stall it. That's something to keep in the back of your head though. You could hook an ohm meter to the crank sensor and wiggle the wires and see if there is any momentary disconnect, only because after replacing the crank sensor it was fine for a year...that holds water. I would hate to see you disconnect it to force a relearn but are the leads sound and clean?

Throttle body: The throttle plate could close briefly and drive you crazy. Not sure how this could happen but anything is possible.....is it clean?

Have you checked the battery terminals, behind the terminals, loose bolts, bad grounds, what voltage do you have at idle from a DMM?

My wife's friend had electrical issues with the Nissan and the battery had 12-12.1V under high-beam load for 2-3 min with the engine off. When idling it would sit at 13.2-13.4 and to me that seemed too low and would even hold that voltage under load. I wiggled the signal wire at the alternator and the voltage jumped to 14.5...been fine ever since.

You could try resetting the PCM harnesses to ensure a clean contact, clean the TB harness, clean all the sensor leads you can get to and perform the TB relearn. I know you don't believe 100% in the TB relearn process but it's worth a try in this case I would think....what's to lose?

 

[The_Roadie]

It has the egr where its on the passenger side of the engine towards the top right next to the transmission dipstick. It looks like its called an air check valve.

That's the issue. We never refer to that as an EGR anything because exhaust gasses aren't recirculated through it or any other path. SAIS air gets pumped into the exhaust manifold for 20 seconds on a cold start through that solenoid valve.

 

[CaptainXL]

Without driving around with a Tech 2 this is going to be difficult.

My suspicion as well. Most threads covering the same issue on other forums state that the owner brought it to the dealer and it sat there for days/weeks because they couldn't replicate the issue. I am not interested in replicating the issue, I would like to be more proactive such as checking PCM software/hardware version and such. Just need someone who has Identifix or some other common cause database for mechanics. It would go a long way to help me pinpoint the area in which I should be looking.

With all the PCM and battery disconnecting I have done...this seems more like a bug. Electrical possibly...but could be that a PCM A/D converter is on it's way out as well.

When this thing purrs along the highway, all day, it runs like a top correct?

For the most part, yes. If the temperature is 70 or below it runs like a top! If the outside ambient temp is hot/humid the engine can seem pretty weak on power. Sometimes it feels like it never came out of second gear when taking off at a light. You know what starting out in second gear feels like...yeah that.

Due to the fact that the engine runs very well in cooler temps says to me that the engine is in excellent mechanical condition. so I am not even going down that path. My efforts are more focused on the computer controlled aspects of the vehicle.

Throttle body: The throttle plate could close briefly and drive you crazy. Not sure how this could happen but anything is possible.....is it clean?

I clean it regularly. Smooth operation is noted.

Have you checked the battery terminals, behind the terminals, loose bolts, bad grounds, what voltage do you have at idle from a DMM?

My wife's friend had electrical issues with the Nissan and the battery had 12-12.1V under high-beam load for 2-3 min with the engine off. When idling it would sit at 13.2-13.4 and to me that seemed too low and would even hold that voltage under load. I wiggled the signal wire at the alternator and the voltage jumped to 14.5...been fine ever since.

At idle the engine consistently charges the battery at about 13.2-13.4 volts. Never really seen it go above 14 unless I left the lights on or something and it needed to charge more. Or if it was a really cold morning less than 45F or so and it was a cold start. This is consistent with the parameters in the service manual.

You could try resetting the PCM harnesses to ensure a clean contact, clean the TB harness, clean all the sensor leads you can get to and perform the TB relearn. I know you don't believe 100% in the TB relearn process but it's worth a try in this case I would think....what's to lose?

All PCM contacts are clean and I have new battery bolts.

I am aware how some might think that the throttle body might have a relearn procedure but the throttle body itself has no logic in it to retain throttle angle. Also when replacing or troubleshooting the throttle per the service manual there is no formal relearn procedure given. The PCM adjusts the throttle angle at idle to maintain rpm and fuel/air ratio. The PCM is constantly adjusting the throttle. If there is a problem with the PCM sending and receiving analog signals to the throttle then a CEL would more than likely be set. This is due to the way in which the PCM receives inputs from both the pedal position sensor and throttle potentiometers. It's a checks and balances type system that works rather well. Wiping the PCM memory by disconnecting the battery or pulling fuses will clear any learned throttle angles but those angles are just a cheat sheet type of deal for the PCM. Even if the PCM never had any learned throttle angles in it's memory it shouldn't take very long for the PCM to figure out how to deal with a certain situations involving temperature or barometric variations. And on top of that it would already have predefined throttle angles in the software. So it would already be very close to optimum.

On the other hand if there was a scenario outside of the PCM's control such as a leaking injector or vacuum leak then the PCM would have to wait until the engine went into closed loop to perform any fuel trim adjustments to bring the idle back to ideal. A problem with idle on a cold start after disconnecting the battery is a strong indicator something is amiss and should be investigated.

 

[kickass audio]

ohhhhh, well now the more you know. lol. Thanks for the correction guys.

OP, when you died out, did you have any warning lights on the dash at all? When I stalled I had no warning lights at all, nothing for voltage, oil pressure, check engine, check gauges, not a single thing. Idk about compression testing on this engine so I can't chime in on that but how about a fuel pressure test, just to rule out if your pump is bad or not. I don't think it would be but it never hurts to look. I'm curious what your fix would be since mine just went away after all the parts I listed were replaced.

 

[CaptainXL]

ohhhhh, well now the more you know. lol. Thanks for the correction guys.

OP, when you died out, did you have any warning lights on the dash at all? When I stalled I had no warning lights at all, nothing for voltage, oil pressure, check engine, check gauges, not a single thing. Idk about compression testing on this engine so I can't chime in on that but how about a fuel pressure test, just to rule out if your pump is bad or not. I don't think it would be but it never hurts to look. I'm curious what your fix would be since mine just went away after all the parts I listed were replaced.

Well stick around then. I plan on nailing this issue once and for all.

I will monitor the truck over the next few days. Will start it up in the morning each day and let it idle to see if all electrical power is missing from the gauges or not.

If I don't get anywhere I am going to start swapping out parts from junk yards and stuff. Cheaper to do that then buy new parts just to test a theory.

 

[kickass audio]

It isnt losing power to the gauges when mine died out on me. I watched the oil pressure gauge slowly go to 0, the rpm gauge instantly went to 0, the temp gauge stayed at the temperature the engine was operating at and then the volt gauge was very slowly creeping down. I have a ton of batteries in my truck so it takes a long time for my voltage to drop and your voltage sounds kinda on the lower side. I have an aftermarket high output alt and I never get lower than 14.3v if its hot and I am loading it down heavily from my system. The way mine behaved was if you had the engine running for awhile and shut it off and then turned the key to run but did not have it started and firing except it had no dummy lights on. I know the lights work on the cluster because when you shut it off and back on it goes through the initial test to show the lights working and every light comes on in the cluster.

When it died on you did it sputter or was it a very smooth shut off where you couldn't feel it? I never felt mine shut off when it died. I only noticed it was off because my power steering was off and the wheel was harder to turn and the truck didn't go anywhere when I hit the gas. lol. How you are describing the slow starts as if you are going from a dead stop and trying to move out of second gear is EXACTLY what I experienced with my truck before my catalytic converter was cleaned out. 2 times I would get the reduced engine power light and it would then go out on itself. It is a really funny thing and I wish I could be of more help to pinpoint what your problem is.

 

[gmcman]

At idle the engine consistently charges the battery at about 13.2-13.4 volts. Never really seen it go above 14 unless I left the lights on or something and it needed to charge more. Or if it was a really cold morning less than 45F or so and it was a cold start. This is consistent with the parameters in the service manual.

Your voltage does appear to be low, I believe the minimum is 13.7 or 13.8V but regularly above 14 almost all the time.


I am aware how some might think that the throttle body might have a relearn procedure but the throttle body itself has no logic in it to retain throttle angle. Also when replacing or troubleshooting the throttle per the service manual there is no formal relearn procedure given. The PCM adjusts the throttle angle at idle to maintain rpm and fuel/air ratio. The PCM is constantly adjusting the throttle. If there is a problem with the PCM sending and receiving analog signals to the throttle then a CEL would more than likely be set.

I agree there is no special "chicken dance" for the relearn, but the PCM does need to re-establish the throttle angle to quickly achieve idle when you let off the gas, the same way it adjusts fuel for a given driving scenario. When I let the TB go through it's steps of the re-learn I posted then it drives fine from the start.

The PCM uses a stored value that has worked and adjusts from there. Perhaps someone with a TECH2 can chime in but I'm almost certain there is a readapt field for the TB to avoid driving around trying to establish it....correct me if I'm wrong. When my TB harness was cut, I watched the guy trying to get my TB to work and he said he re-adapted it....I did not see the screen at that moment so I don't know for sure.

When your engine is running, wiggle this signal lead to the alternator. You can try cleaning it first but just one thing to try since your alt votage is low, probably not the root cause of your symptoms but I would check it out, this fixed my charging issues.

 

[The_Roadie]

I agree there is no special "chicken dance" for the relearn, but the PCM does need to re-establish the throttle angle to quickly achieve idle when you let off the gas,

Agreed. The behavior of the system leads me to conclude that the PCM has a special subroutine for "what to do with the throttle plate angle when the AC compressor cycles on and off at idle". The PCM knows the compressor is about to cycle on and off, because it's in charge of the AC compressor relay. I believe the PCM ANTICIPATES the load of the compressor, and adjusts the throttle body in preparation for that event so the RPM doesn't droop to stall-out numbers. An aging throttle body with restrictions and possible stickiness around the edge of the plate can be adapted for over time, but when owners (thousands of them) discharge or replace their batteries, the PCM loses this adaptive table. The baked-in OEM settings can't accommodate fully for how bad throttle bodies can get, so impaired idle and stall-out performance results, triggered by unanticipated compressor engagement. And then the magic cure of cleaning the throttle body is the countermeasure.

I think a leaky intake manifold can mess up the system in a similar way, since the MAP is measuring the vacuum at a distance far away from where the leak might be down near the cylinders. And that leak may be temp sensitive.

 

[gmcman]

Agreed. The behavior of the system leads me to conclude that the PCM has a special subroutine for "what to do with the throttle plate angle when the AC compressor cycles on and off at idle". The PCM knows the compressor is about to cycle on and off, because it's in charge of the AC compressor relay. I believe the PCM ANTICIPATES the load of the compressor, and adjusts the throttle body in preparation for that event so the RPM doesn't droop to stall-out numbers.

Sounds like a particular sequence correct? Increase TB angle then engage AC compressor, in milliseconds? Cap't I believe has bypassed the AC so this is happening regardless, but always seems to behave in or near the same scenario.....slow maneuvering or when cold.

I say he needs to at least try the "relearn" and see what happens. Perhaps there is a lost or unlearned parameter in these situations, but either case it's worth a try. If that doesn't fix it at least it's a base that's been covered.

 

[CaptainXL]

When it died on you did it sputter or was it a very smooth shut off where you couldn't feel it? I never felt mine shut off when it died.

Same here. It dies very smooth. Never heard it shutoff with the kids playing in the background.

Bill and gmcman. Good info. Not really going to disagree. I think we are pretty close to being on the same page.

 

[CaptainXL]

When your engine is running, wiggle this signal lead to the alternator. You can try cleaning it first but just one thing to try since your alt votage is low, probably not the root cause of your symptoms but I would check it out, this fixed my charging issues.

The other day I left the keys in the ignition as I was doing some parking brake and stabilizer link work. Came back an hour later to find the battery was dead (couldn't take keys out). Fed up, I went to Sam's club and replaced the battery with a Duracell AGM. I figured it was time.

My jaw dropped to find that the alternator is now charging it over 14 volts all the time. It never drops down to 13.xx volts like before. It's been cool here the past week so this may not mean anything. I guess we will know for sure when it warms back up. The old battery tested good but it seemed to have very little reserve.

 

[gmcman]

That's great to hear, hope it's fixed. Generally if you have a cell shorting out it pulls the battery down and it's hard to start if it even starts. Alternators are screwy and your stalling issue sounds like the alternator not putting out which brings me to asking did you ever jiggle the signal wire at all before you changed the battery? You should always be above 13.4 volts and I think these platforms even spec 13.8, the electronics don't like it when the volts are low, 13.2-13.4 is too low.

Like I said earlier....the wife's best friend's Altima had odd electrical issues.....12.1 V with engine off, 13.2 with it running. Cleaned the signal connection and it's now 14.4 running and all her problems went away. Alt was putting out but not enough.

 

[CaptainXL]

That's great to hear, hope it's fixed. Generally if you have a cell shorting out it pulls the battery down and it's hard to start if it even starts. Alternators are screwy and your stalling issue sounds like the alternator not putting out which brings me to asking did you ever jiggle the signal wire at all before you changed the battery?

No never giggled anything unless it was by chance when removing the battery cables.

You should always be above 13.4 volts and I think these platforms even spec 13.8, the electronics don't like it when the volts are low, 13.2-13.4 is too low.

Can't remember what I was getting but 13.4 sound right. I remember looking in the service manual and the voltage seemed nominal.

Like I said earlier....the wife's best friend's Altima had odd electrical issues.....12.1 V with engine off, 13.2 with it running. Cleaned the signal connection and it's now 14.4 running and all her problems went away. Alt was putting out but not enough.

One of these days I am going to rebuild the alternator. Curious to know how much carbon is left in the brushes. I really don't think there are any loose wires anywere. I checked a lot of that stuff when I got the truck a few years ago. But will check again cause I am OCD like that.

And...just another update. The charge gauge still shows over 14 volts when the truck is running. The truck seems to run a bit smoother but this could be a mind effect.