Hey guys, so I was driving around my college campus today at fairly low speeds and stopped to drop someone off. Then when I went to leave my car just hesitated and almost stalled, almost like trying to start out in 3rd gear, so I checked and I definitely was in first. So I put it in neutral and my car continued to idle horribly around 750 rpm and sounded very bad almost like my exhaust was coughing. So I shut it off, waited about 20 seconds and it started up perfect and went back to normal idle. then in about a minute i revved it a little and it went back to idling horribly. So I can drive it fine if I start it and drive right away but when it idles for about a minute it starts to go into that horrible shuttering coughing mode. My coolant temp is normal and when I rev I have a small amount of black smoke. I did drive it after starting it back up and I seem to have full power and boosts fully. Everytime I restart it runs perfect and revs perfect but eventually goes to horrible idle if you rev it after about a minute of idle, during this bad idle you can kind of rev it but is very choppy and sparatic.

I recently installed the zzp stage kit but has been fine for about a month. I also recently cleaned the throttle body. My engine light also came on and Im going to check for the code tonight.

I was thinking a possible injector issue or maybe a dirty MAF sensor?

Let me know what you guys think, thanks in advance!

 

Here are the codes:

P0171

P0507

 

P0171 is an o2 sensor being to lean, and P0507 is IAC higher RPM than expected... which can be a vacuum leak.
Its possible that you have a vacuum leak and that is leaning out your air fuel mixture ratio and your 02 sensor is catching it.

 

Yeah, where do you think the leak would be at? An injector?

 

Look at all vacuum hoses first, if you cant find it take a can of maf cleaner or something and start spraying areas. When you hear a change in idle your leak is near.

Also, if there is something weird happening to your car...... Do go out and do a full WOT pull. Thats just stupid.

 

Well I went out and started it and let it warm up fully. It idled and revved perfectly fine for about 20 minutes. So not sure whats up but Im gonna try to clean the MAF today

 

Well I cleaned the MAF and nothing changed, but I was driving it tonight and after sitting idle for about 30 seconds it happened again and the engine light came on again with Im guessing the same codes. It proceeded to happen another 2 or 3 times. It drives perfect otherwise so it seems like something with the computer at idle

 

Disconect your battery for 15min

 

Could that mess with my zzp tune?

 

Your tune will be ok
Your just reseting you pcm. No worries on the tune

 

Heres a video of what happens, sorry bad audio. Its at first idling normal at 1k and I barely hit the gas and it goes down to 500 then fluxuates between 500-750 meanwhile sounding horrible, then I try to rev it and its very unresponsive but eventually responds for a second but then goes back down to 750 and sounds horrible. After this I shut it off and started it in 10 seconds and started and idled perfect......

http://s187.photobucket.com/albums/x...0_235058-1.mp4

 

Try to do what i said then check.

 

Will do. Thanks.

 

More info

po507 cobalt ss - Google Search

Check vacum leaks with an tester, might be tune

 

I unhooked battery it didn't help. I'm gonna try to find a vaccum leak now

 

clogged cat? I know our cars are notorious for that issue.

 

Is there a way to check for that?

 

Cats were recalled, call Chevy to verify you are/arn't part of the cat recall.

 

dunno how to check but know it is a frequent issue and can cus the car to run like poop

 

the car runs 100% perfect other than when you idle for about a minute then hit the throttle it goes into suck mode. it will idle forever perfect at 1000 rpm but if its been more than about a minute, once you hit the throttle it starts coughing and shuttering. but turn the car off for 10 seconds and start it and its perfectly..........whaaaaaaaaaaaaaaaaaaaaaat

Could this have anything to do with using a bad grade of gasoline? because last tank I thought I was putting in 93 but later realized that for some reason all they had was 87 so I put like a 3/4 tank of 87 in but since then I put a new tank of 93 in after using all the 87. the problem started soon after putting the new tank of 93 in.....

 

Check for vac leaks. If there arent any then more info need. Does it only do it once the car has warmed up?

 

Yeah only happens when its warmed up. Whats the best way to check for vac leaks?

 

^check the hoses and if everything checks out if you have maf cleaner or starter fluid (something like that) spray everything that can possibly have vacuum.

 

and if the idle changes there is a leak.

BUT, it only happens when warm, you have a lean code yet shoot black smoke, I want to say you have an issue with your 1st o2 sensor.

 

haha yah thanks for finishing my statemnet. I came back to edit it to say that.

When warming up the car is in open loop could be part of why its not happening.

I tuned a guy that the car was fine warming up then when warm (closed loop) the car would idle hunt and run like ****, turns out the fender rubbed a huge hole in the intake.

If it was a O2 sensor issue wouldnt he have a code for that?