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post #1 of 5 (permalink) Old 11-06-2015, 05:29 PM Thread Starter
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Question 2006 Cobalt LS 2.2 / Engine Shuts Off / Reduced Engine Power

Hello! This is one of the best forums for Cobalts, so I am here asking for advice from any Cobalt gurus that can help with my engine stalling problem.

I'm posting my problem with plenty of details from the last few months.

My Car: 2006 Cobalt LS, all stock except for rims and a stereo deck. 5 speed manual, ecotec 2.4L.

Some History: 165k miles, 3rd owner, ran perfect for the first 4 months I owned it. About a month ago the engine started stalling and shutting down at random intervals (from a dead stop, cruising, accelerating).

Problem Description, Details, and Notes:
For the last month, engine shuts down or stalls and misfire (tach drops to 0) at somewhat random intervals. On a 30-45 minute commute to work, I might need to restart it 2-8 times. This occurs MUCH MORE FREQUENTLY when it HOT outside and I have the A/C on (it is still 85 degrees here), and the engine has been fully warmed up and driven for at least 20 minutes. The engine runs fine when it is cold. The engine stalling happens less frequently when it is raining and it is cooler outside.

For the last 4 days, after driving for about 30 minutes and restarting several stalls, the engine restarted with "engine power reduced", but the car is too slow to drive safely. I then pull over to side of road and wait a couple minutes. I can then restart and drive without the "reduced engine". After this happens, the check engine light is on temporarily, but it goes away after a couple of short trips. This has happened to me about once a day for the last 4 days which prompted me to really try to get this fixed, this is dangerous in traffic.

Normally if I'm cruising and it stalls, I'll use the clutch the restart the engine. I can't do this when it completely shuts down and wants to restart with "engine power reduced". I am forced to use the starter to get into limp mode, pull over, wait a couple minutes, and then restart and hope it doesn't happen again.

Tachometer is all over the place when stalling is occurring. Drops down to 0, I gas it, goes back up, goes back down, coughs, goes back up, stalls again, and then returns to a normal idle. Oddly, I noticed if it is stalling/coughing, at wide open throttle the car accelerates and stops choking. WOT seems to help prevent the stalling for a very short time. Oddly, sometimes the tach drops down to 0 but the motor is still running, I constantly use gas pedal to check to see if engine is still on. Car feels like a bucking horse going down the road using WOT to prevent stalls though, and I feel like I'm stressing the motor mounts and drive axles while in lower gears.

Notes, diagnostics and what I have done in the past week to try and correct this:

Car is normally idling stable at about 900 rpm warm, 1100 rpm cold, until it decides to stall or cutout while driving.

Air filter is clean.

I removed the throttle body for a careful cleaning like recommended on this site. (To be safe I followed the advice and disconnected battery, left key out of ignition, and carefully cleaned with a toothbrush and rag for wiping).

I cleaned the MAF sensor with MAF cleaner from parts store.

I have checked and reseated every single fuse and relay under the hood and in the interior.

Car battery is fine, blower, lights, accessories, starter, etc work when engine shuts down. I have cleaned the terminals of course, and tested the voltage (12.5v), but I did not have the battery load tested yet.

Cooling appears normal, I've been watching it closely lately. Normally around 190-205 degrees. Long idling when it is hot outside, and coolant temp goes up to 210-225. I think this is normal?

Check engine light is normally not on. It just started to light up a few days ago after a stall/shutdown to "reduced engine power". Again, this goes away after a few trips. CEL does not light up during its normal stalling or driving routine. Only when it goes into limp mode.

I had parts store pull these codes for me:

P0121
P0336
P0068

This doesn't make much sense to me. Too many different things going on here.

Oh yeah, one last odd thing I remember. When stalling became more frequent and I experienced the first "engine power reduced" mode, for some odd reason the DIC oil life gauge was reset to 100%?

With the engine warmed up and idling, if I tap on underhood fusebox and PCM with my hand, there is no change in idle RPM.

I just purchased a new Ignition Control Module at AdvanceAutoParts, I am going to replace that tonight to see if it fixes my stalling/shutdown after warm up. If it does not fix the problem I can easily take it back for a $80 refund.

What do you guys think it is, or what should I try next if new ICM does not help? I'll post results later tonight.

Thank you in advance for your help and advice.

Matt

Last edited by jmatrix; 11-10-2015 at 01:48 PM.
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post #2 of 5 (permalink) Old 11-06-2015, 06:49 PM
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Sounds like you have a frayed wire touching somewhere. Or bad ground between engine and chassis.

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post #3 of 5 (permalink) Old 11-08-2015, 10:05 AM Thread Starter
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Quote:
Originally Posted by Coby7 View Post
Sounds like you have a frayed wire touching somewhere. Or bad ground between engine and chassis.
Hi Coby7,

I was thinking something definitely electrical as well. As I have been probing around the motor I noticed all the plastic heat sleeves over the wiring will pretty much crumble to dust with your bare hands which had me wondering. This car has been in the hot south Florida sun all its life.

For the most part, the new ICM I have installed seemed to fix the immediate stalling issue when the engine is warmed up. I've driven 50 miles since in traffic with a passenger load over the last couple days and it has not stalled on me once. I haven't had a chance to test it when it gets hot here (85+) since it cooled off a little recently. It kind of makes sense though, I came across a post on a SS forum where they were talking about how the ICM can overheat since it sits directly on top of the engine.

My 1995 Camaro had similar behavior before I junked it (shutdown after warmup, and shutting down quicker the hotter the outside ambient temp is, no CEL's). I've replaced 2 ICM's on 2 Chevy's in the past year. HEHE


All in all I'm happy I replaced the ICM - I can get and forth to work without stalling. I am still getting some hesitation and choking here and there but no where near as bad as it was with the stalling and engine shutdowns or reduced power modes. I am still getting 24 MPG around town. I think this is good mileage for this car. Gas is cheap right now!

I think it might need a throttle body because after I first installed the ICM, I noted the engine did surge 1 time on me (with my foot off the accelerator, the car continued to increase in speed). But not since then though.

Replacing the ICM was really easy, 3 torx screws and a electrical plug that takes a few minutes to figure out.


For now I'm rolling down the road again, and most importantly SAFELY....

Last edited by jmatrix; 11-08-2015 at 11:48 AM.
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post #4 of 5 (permalink) Old 11-10-2015, 01:41 PM Thread Starter
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I have now replaced the coil packs and ICM and the engine runs much better.

Starts easier, and doesn't stall, buck, jerk, jump, shutdown, stall anymore when driving in hot or warm conditions (it was 89 degrees in Miami today, we're breaking temp records) in traffic with the AC on full blast.

It still hesitates a bit when it is hot though. I see the RPM's drop for a second or two once or twice after 25 miles in hot conditions.

Glad I can safely get back and forth to work now though.

Last edited by jmatrix; 11-10-2015 at 09:03 PM.
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post #5 of 5 (permalink) Old 11-14-2015, 04:39 AM Thread Starter
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OK, stalling after warmup came back.

I was on my way to work yesterday when my car stalled going down the road and wouldn't restart for 5 minutes.

This time I replaced the CKP sensor, now the motor is running like it is brand new.

It also fixed a strange vibration I originally thought was coming from the clutch. When engaging the clutch from a dead stop, my engine would start vibrating up and down, and vibration transmitted to dash/steering wheel. I thought it was a problem inside the clutch and lived with it. After a CKP sensor installed, my clutch vibration problem was fixed as well.

UPdate: CKP sensor DOES not solve clutch vibration issues.

Last edited by jmatrix; 11-17-2015 at 09:20 PM.
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