intermittent stalling

signalnc

Original poster
Member
Dec 28, 2012
249
I've been having an intermittent stall issue the past few months. Always at idle, mostly in park while warming up. It happens about once every 2 weeks. I have cleaned the throttle body, installed new 41-103 plugs, replaced cam shaft position sensor, replaced 3 bad coil packs--and 3 good coil packs. ....I realized today that the a/c compressor comes on when you hit the "auto" button on the comfort controls. This is my wife's vehicle that I seldom drive. I did a little experiment today and it seems when the compressor is on, the idle gets a little unsteady. It seems to wobble, or go down, to about 500 rpms every so often( a minute or two) and not at a steady interval. Not enough to stall. Volt gauge is showing 14. I am planning on testing the battery under a load tomorrow. Is there anything else I can check?
thanks.
 

The_Roadie

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Nov 19, 2011
9,957
Portland, OR
Lift the hood and confirm that the idle gets flaky exactly when the AC clutch engages. You've done almost everything that people have thrown at this problem except replace the CPAS itself. For $50, I'd do that next.
 

tbuckalew14

Member
Nov 20, 2011
380
sounds like the issue I was having a couple months ago. Just kept changing things and following engine trouble codes. First I had an issue with the camshaft solenoid. Then got as trouble code for the camshaft sensor. After replacing them the stalling went away. Just make sure do NOT buy an aftermarket cpas. I made that mistake trying to save 20 bucks.
 

bastenblood

Member
Dec 22, 2011
23
the roadie said:
Lift the hood and confirm that the idle gets flaky exactly when the AC clutch engages. You've done almost everything that people have thrown at this problem except replace the CPAS itself. For $50, I'd do that next.

The rpm on mine always drops every minute and because the ac compressor clutch engage , even if it's set to off . Can I
just change the clutch or what ?
 

signalnc

Original poster
Member
Dec 28, 2012
249
I didn't have time to get a load tester today, probably tomorrow. I did sit in the car for a while after my wife got home. I hooked my fluke 287 to the battery and watched it while I sat in the drivers seat. While idling with comfort controls set to "off" I had between 14.50 14.54 volts without much fluctuation. When I pressed "auto", thus turning the air conditioner compressor on, I saw a slight dip to 14.28, then right back up to 14.48--it was more like a blip to 14.28. Load testing it tomorrow, but I think it's ok.

what I did find is that 10 seconds after the a/c compressor kicks on(I hear a click when it kicks on), the rpm's dip to about 500. I don't have anything to measure rpm's other than the dash, but it is consistent. I left the a/c running for at least 5 minutes, every time the compressor kicks in, almost exactly 10 seconds later there is a dip in the rpm's. It did not stall, but a few times it felt if it dipped any lower it would have. I used a stopwatch to measure the seconds, so I know it was correct.

I hope this makes sense. thanks for all the input.
 

The_Roadie

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Nov 19, 2011
9,957
Portland, OR
Your alternator and battery sound fine. How many miles do you have? Can you get a scan tool on the system and see if the O2 sensor data is fluctuating up and down at the proper 1-2 Hz rate? At 100K miles, many folks do both the plugs and the O2 sensor. A sluggish sensor (it gets gunked up from the exhaust stream) could show up as a mixture error that gets adjusted a few seconds after the engine load changes. Or the CPAS, as I also mentioned.
 

signalnc

Original poster
Member
Dec 28, 2012
249
the truck has 130k on it. O2 sensor has not been changed since I've owned it. Bought it with 33k or so.

I have been going to the auto parts store and having them read my codes when they have popped up. I'll go down there tomorrow and ask if they can read that. As long as their tool can do it I'm sure they'll be more than happy to read it. At this point I've got over $2300 out of my pocket between my Jeep Cherokee and the trailblazer in the last 3 months, other wise I would just buy one myself to have on hand.

again, thanks for your help
 

tbuckalew14

Member
Nov 20, 2011
380
signalnc said:
the truck has 130k on it. O2 sensor has not been changed since I've owned it. Bought it with 33k or so.

I have been going to the auto parts store and having them read my codes when they have popped up. I'll go down there tomorrow and ask if they can read that. As long as their tool can do it I'm sure they'll be more than happy to read it. At this point I've got over $2300 out of my pocket between my Jeep Cherokee and the trailblazer in the last 3 months, other wise I would just buy one myself to have on hand.

again, thanks for your help

with that many miles, it's probably time to change the o2 sensor anyway...assuming you have a few extra bucks for parts.
 

signalnc

Original poster
Member
Dec 28, 2012
249
LOL-I'm not broke yet..according to my kids I have an endless supply of money....I will probably just go ahead and change the o2 sensor anyway. I know where it's located. Is there special tool to remove it? or is it just a metric or standard socket size. I tried looking it up on Alldata but I can't find it.
 

gmcman

Member
Dec 12, 2011
4,656
I'm curious as to why you had 3 bad coilpacks? Over what time period were they all changed? Are you sure you don't have a vacuum leak? Did you reconnect the big black hose under the large black intake resonator?

Are you getting any kind of moisture in the coil pack electrical connectors?

How old is the fuel filter?
 

signalnc

Original poster
Member
Dec 28, 2012
249
fuel filter is new..first coil pack went Christmas day, then another one went out end of January-beginning of February. The last one went out 2 weeks ago. So basically 3 in 3 months. I just bit the bullet and replaced the other 3 a week after the last one went. No moisture on the coil pack. The other 3 might have lasted for years. I just wanted all new ones. I didn't want to take a chance of one going out while I was away and my wife was home with the kids. Everything was reconnected correctly and tightened down.
 

gmcman

Member
Dec 12, 2011
4,656
What I'm referring to is the physical connection of the coil and the coil pack. Did you also use the di-electric grease between the coil and the spark plug?

I would also check for a wire possibly shorting along the harness for the coil packs. Very uncommon to lose coil packs the way you did.
 

signalnc

Original poster
Member
Dec 28, 2012
249
I also thought it strange to loose 3 in 3 months. I will check the wiring harness. I did not use di-electric grease when I replaced the coil packs. I can get some tomorrow when I get the o2 sensor.

The coil pack electrical connectors seemed fine to me. No moisture that I could tell. I will pay more attention to them tomorrow. I'll look at them for signs of moisture.

- - - Updated - - -

no--I do not spray the engine with anything for cleaning
 

gmcman

Member
Dec 12, 2011
4,656
gmcman said:
What I'm referring to is the physical connection of the coil and the coil pack.

That was supposed to read "the coil pack and coil pack harness."
 

signalnc

Original poster
Member
Dec 28, 2012
249
roadie--I just had all the fluids changed. That's part of the $2300. I think the bill for trans, transfer case, front and rear diff, and coolant was $400 or $500? can't remember exactly.. and also had the fuel filter changed.. I didn't have the time and it was way overdue.
 

signalnc

Original poster
Member
Dec 28, 2012
249
I got a Bosch o2 sensor. That's all they had. Should I return it and order a delco online or will the Bosch be ok?
 

Voymom

Member
Feb 3, 2012
2,523
I had this VERY same issue with my Envoy, I even have video's of the RPM's dropping, had it stall on me a few times, once going down the highway, which was the scariest. I had changed the CPAS, fuel filter, did compression tests, cleaned injectors, did fuel compression tests...I spent about $400 if not more trying to rule out the root cause, and nothing, NOTHING I did worked. I had no codes to go by, I had shop after shop run diagnostics, and finally I just said F&^% it!! I was just going to drive the damned thing until A: I got a code to help me diagnose the issue or B: Drive it until the absolute end of it's life..I was so freaking fed up.

Then in December my husband got me the PCM4less tune with a new PCM instead of using the original one, and low and behold...my issues stopped. I have not had a single issue with stalling, sputtering, dropping RPM's...nothing, nada, zilch lol

Some people think that the computer wasn't the issue, or something just needed to be calibrated..whatever their belief or opinion is, I know that my truck stopped having this issue the moment my husband put the new PCM in. I had a shop re-calibrate a few things on the truck and it did absolutely no good, I spent $50 per trip(Free with big boobs :raspberry:) to have them hook up their scanners, just to tell me that they can't figure out what was wrong, even leaving the truck in a shop for a 24 hr diagnostic warranted not a damn thing! Maybe, just maybe this is something you should look at, I know a tune isn't in everyone's budget, but if you could get a hold of a donor PCM and just give it a shot? The worst that will happen, is that it doesn't fix the problem and your back at square one...
 

v7guy

Member
Dec 4, 2011
298
The I6 seems to be very temperamental about it's spark plugs and O2s, some people haven't had problems, most have. Personally I wouldn't chance it. The correct part number is 213-1551. Find it here
ACDelco 213-1551 OE Service Oxygen Sensor : Amazon.com : Automotive

you may find it elsewhere, this is the first thing that came up via google.


Voymom also brings an alternate possibility to the table. Something to consider.
 

The_Roadie

Lifetime VIP Donor
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Nov 19, 2011
9,957
Portland, OR
signalnc said:
I got a Bosch o2 sensor. That's all they had. Should I return it and order a delco online or will the Bosch be ok?
Bosch runs fine, unless and until it throws a code for "O2 sensor heater circuit". The sensor is still operating perfectly, and won't affect driveability, but the Bosch sensors just draw a bit different (too little or too much, I don't know) heater current to satisfy the PCM's built-in diagnostic limits. If it ever does that, then put in the AC Delco. Until then, just watch for the code.
 

signalnc

Original poster
Member
Dec 28, 2012
249
thanks for the explanation on your similar issue voymom.

I'll put the Bosch in today and see what happens. If it throws a code I'll order a delco and take it out ..thanks
 

Voymom

Member
Feb 3, 2012
2,523
signalnc said:
thanks for the explanation on your similar issue voymom.

I'll put the Bosch in today and see what happens. If it throws a code I'll order a delco and take it out ..thanks

It might not throw a code, but it could very well cause the truck to run shittier than normal...just a heads up! And you're welcome :thumbsup:
 

gmcman

Member
Dec 12, 2011
4,656
Signal, don't forget that grease. Do you have access to a scan tool with live data to view the O2 sensors?

Other than water being inside the coil pack connectors I can't really see how you managed to burn up 3 of your coils shortly after you changed the plugs other than maybe the absence of the di-electric grease. Did you try to gap them? Reason I ask is the electrodes don't like to be bent as they are set from the factory...always wise to check though.

What does your air filter look like?

Did you let the ECM learn the new idle position after you cleaned the throttle body? Wouldn't hurt to let it go through the steps. I unhook the throttle body harness as well as the battery cable before I begin the cleaning. After about 30 minutes, reconnect the TB then the battery and turn the key to "ON" and don't start it and don't touch the accel pedal, and don't turn the key off.

Let the TB click around a few minutes and after about 10 minutes (don't remember exactly how long but by the time I clean everything up it's about 10 min) no less than 5 min though...then start the engine and again, don't touch the accel pedal. Let the engine run for about 5-10 min at idle and see what happens.
 

signalnc

Original poster
Member
Dec 28, 2012
249
well-I didn't get the o2 sensor in 'cause the thing is like tight as can be. So it's sitting in the driveway with aerokroil on it for the night. I'll try again in the morning.

I burned one coil with original plugs, and 2 with autolite's--now I have ac delco plugs.:smile:...I did gap the delcos because they were all over the place when I got them. I used needle nose pliers and was very careful not to touch the iridium point. The first was I was nervous but then after that it really wasn't hard. Just have to be careful.

I did not do the steps to relearn idle position after I cleaned the throttle body. I just hooked everything back up and started it. I might try that tomorrow.
 

gmcman

Member
Dec 12, 2011
4,656
signalnc said:
I did not do the steps to relearn idle position after I cleaned the throttle body. I just hooked everything back up and started it.

I would definitely do that first.

With the plugs, well....at least the way I do them, is check the gap and if they are no more than .002 out, I will leave them alone. I don't like to stress the electrode on these plugs, they aren't like the ones way back in the day..these seem to be more brittle. Lord help you if one breaks and gets stuck under a valve seat. If one is way off then take it back.....they should all be good to go.

The O2 sensor shouldn't be that stubborn, Try to break it loose with a cold exhaust first then snug it back down, then go and perform your TB relearn. If you need to change the O2 then work on that afterwards.

You really need the grease on the tip of the coil lead. Place a pea-sized amount inside the boot right at the lead..should be enough. You may have high resistance at the plug tip. Best to do this with a cold motor.

Did you use an inch-pound torque wrench to install the coil pack bolts?
 

signalnc

Original poster
Member
Dec 28, 2012
249
coils are tightened to spec:

from alldata:
"Tighten
Tighten the ignition coil retaining bolts to 10 N.m (89 lb in) ."

10 nm is newton meters. so converted it is 88.5 inch pounds or rounded up to 89.... about 7 foot pounds
 

signalnc

Original poster
Member
Dec 28, 2012
249
I replaced the o2 sensor and did the throttle body re-learn, as well as wipe out the throttle body while I was at it. It wasn't real dirty, more like a little dusty. I had just cleaned it a few months ago. Didn't really want to do them separately and check to see which one had the most impact on the idle stumble because of time constraints. But they are both done, along with dielectric grease on the coil packs. Idle seems better. The mysterious stumble 10 seconds after the a/c compressor kicks in is gone. Slight fluctuation in idle with a/c on. Not exact every time. sometimes a slight dip at 12 seconds, sometimes at 14, or 16 seconds. It's hardly noticeable. I'm just being real picky. I would say it goes down a half a "click" on the tachometer. I'm satisfied with it. I'll update if it changes, or gets worse. Thanks for everyone's input.:thumbsup:
 

signalnc

Original poster
Member
Dec 28, 2012
249
just a quick update: after driving it around for about 60 miles of mostly highway driving the idle is steady with and without the a/c running. No more strange dips in the rpm's. thanks again.
 

gmcman

Member
Dec 12, 2011
4,656
Glad to hear. :thumbsup:

Also, the RPM's will drop slightly when the A/C kicks on, then rebound.
 

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