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Discussion Starter #1
I'm having an issue with my 2011 Impala (3.5 v6, 80k miles) that seems to me to be two unrelated problems?

A few days ago I needed to move the car quickly so I started it and threw it into gear really quickly. Before I could take my foot off the brake though I realized that the engine was dieseling pretty badly so I put it back in park and shut off. Tried again and it was still dieseling and running really rough. Tried a third time and wasnt much better but I got it out of the driveway as needed. When I got to
look at it it was an hour later and ran just fine now so I kind of forgot about it.

It drove totally fine for two more days until Sunday when I went to start it - the engine fired up good but then died within about 1 second. Tried several more times to start it but the engine just kept dying quickly. This seems just like a security issue now? A long time ago I had a Dodge minivan that did exactly the same thing if I used the valet key (black?) instead of the normal key (grey?). So I gave up and went to the dealer on Monday to get a spare key (I only had one so really wanted a spare anyway). Of course the car starts and runs fine by now. Anyway I programmed the new key - simple and easy - now both keys work great.

I cant get the problem to come back but am betting it will and will strand me somewhere so I'm driving my backup vehicle for now. I have yet to see any CEL or security lights at all (other than when all lights come on when starting). No security flashing ever or anything like that.

Today I scanned for codes and all I could find was a P0171. Maybe that explains the dieseling and I know its likely MAP or MAF or O2 but cant imagine that would cause the engine to die like it was doing?

I'm stuck because cant seem to find any help on internet that sounds like my issue - not about to let the stealership anywhere near it either as I'm pretty sure they wouldnt have a clue how to fix it.

Car runs super and gets great fuel mileage. Battery is about 4 months old, voltage is good.

Toying with the idea of getting an aftermarket remote starter as maybe the bypass needed for that will help?
 

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I don't want to say Don't get a Aftermarket RS. As i am a person that likes them way more then any OEM... However I will say that if your car is having an issue. ( Don't sound like a Security Issue to me (Not that I am of Authority in this matter)) It would be a shame to spend money on something that isn't likely going to fix the issue...

Lean Bank 1 and 2. Could be a MAF issue, Intake leak issue. O2 sensor.

I will say that if your Security light didn't come on and you were able to program a new key to your car then for sure a Aftermarket RS isn't gonig to help. I would say if that is something you want installed then for sure after your car is fixed and running right go for it...

James
 

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You have an interesting set of symptoms. I experienced the dieseling issue and also had the car nearly stall a few times, and my issue turned out to be the evap purge valve on top of the engine. However, I have a '13 with the 3.6 so I'm not sure how comparable the evap systems are. Here's the thread where I detail my symptoms: http://www.impalaforums.com/chevy-i...09-3-6l-fuel-lean-and-oxygen-codes-fixed.html
 

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Discussion Starter #4
Thanks for the advice. I'll admit its a puzzling issue. I still cant get it to duplicate the start and die issue. Guess I'll just have to wait for it to happen again. I'm not too worried about the dieseling issue since I get super fuel mileage right now. Will have to investigate that evap issue more though - sounds like that could be it.

My code reader lets me see the O2 sensors in real-time and they look to be responding normally. It did suggest to me that the most common reported fix was to the MAP (pressure) sensor, however I think thats a generic fix for all vehicles with that code. Not sure if the Impala even has one of those. I'll likely try cleaning the MAF first though and see if the code vanishes.
Cheers
 

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I started on my issue by cleaning the MAF, of course it didn't work, but hey, that's how diagnosing issues works. Hopefully it's just a dirty MAF, and you don't have to keep trying to figure it all out
 
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