Rough idle. P0411 p0651 faults. Reduced engine power. - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
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post #1 of 7 (permalink) Old 08-12-2015, 09:46 PM Thread Starter
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Rough idle. P0411 p0651 faults. Reduced engine power.

So first things first.... This is my first post. Hello everyone! I don't hate my cobalt. Just frustrated with it. So the issue started on Tuesday. My wife went to drive the car to work (55miles one way) she started it up and it said reduced engine power and was idling rough. She shut it off, restarted it and it ran fine. She went to work. I called her at lunch. Had her start it and same thing. No fault codes came up and she restarted it. No issue. She was driving home after work and she said it was driving different. I got on the Internet and did some research earlier in the day and found a lot of people were having this issue and they just simply cleaned the throttle body and it was good to go. So she got home, she showed me the rough idling and no check engine faults. We ate dinner so it could cool down and then I removed throttle body and cleaned with a rag and carb cleaner. It wasn't horribly dirty but a little dirty. I started up car after putting it all together. And it seemed to be a little better. We go back inside and proceed with our evening. Well I leave for work in the morning an hour before. 55 miles as well. She calls me up saying that her car is running horrible and the reduced engine light is on again. This time with a fault code. Finally. I tell her to shut it off and try to run it again like we did on Tuesday. This time it didn't work. She had to take a sick day since I was already at work and we have no other way to get to work. I get home tonight and check the codes. I have an active p0651 and a p0411 fault code. I start car. Seems to idle fine and take it for about a 5 mile test drive. Pull back into my garage and the idle starts to jump around again. Going from about 550 to 900 Rpms. I think maybe the maf sensor may be the culprit or it still could be the tp sensor. I unhooked the maf sensor while its running rough and didn't really notice a change. Other than throwing other faults. When the sensor was plugged in the parameter was reading .3lbs/min. (I believe) I'm not a car mechanic but I am a master Volvo/Mack tech at our local dealership. Cars are a whole different animal but I'm pretty sure I can figure it out with a little more resources such as you guys. I really think I've got more than just 1 issue. I don't really see how The fault p0411 or p0651 could make an impact on the idle like it is. What do you guys think?
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post #2 of 7 (permalink) Old 08-12-2015, 09:50 PM Thread Starter
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Forgot to mention that when the idle is jumping all over the place the lights inside dim with the idle. Which kinda makes sense since the alternator is probably kicking on and off with the idle fluctuating so bad. I checked all the fuses for the air pump and I was thinking about checking the check valve or possibly the pump. But I still don't know if that could be the culprit for the reduced engine power and rough idle. I'd like to fix those issues before I tackle the pump issues.
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post #3 of 7 (permalink) Old 08-12-2015, 10:19 PM
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https://www.youtube.com/watch?v=5HmNbd-WZ-8

This video is pretty good. I wasn't sure so I started digging around

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post #4 of 7 (permalink) Old 08-13-2015, 04:47 AM Thread Starter
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I watched that video too. Going to check out the air pump. But I don't think that's my idle issue.
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post #5 of 7 (permalink) Old 08-13-2015, 06:25 AM
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Your idle issue is probably a dirty throttle body. I've had to clean all of mine except the 2010, it still only has 62000Kms.

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post #6 of 7 (permalink) Old 08-13-2015, 11:16 AM Thread Starter
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I've already cleaned it. I think I posted that already? I'm not sure. But if I didn't, I took it apart and cleaned it already. Same issues.
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post #7 of 7 (permalink) Old 09-06-2015, 05:07 AM
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I had the same trouble. Check my post and fix. Cobalt hasn't stalled since.
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