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08 Chevy Malibu - Dies when trying to idle, runs fine at higher revs

Lord Tin Foilhat

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Hey guys,

Friend has a 2008 Chevy Malibu that started acting up on her. 160k.

It starts, but idles rough and eventually starves itself and dies within a minute or 2. But initial idle for 5-10 secs is smooth.

If I rev it over 2500 rpm and keep it up, it keeps running and drives fine. No misfires.

No check engine lights. Nothing on the scanner. Resat the fuel pump relay and checked fuses. Resat MAF connector.

I think it's her fuel pump going out. Any other thoughts on what it could be??

Thanks
 

Lord Tin Foilhat

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i would think a bad fuel pump would make things worse at higher rpm.
2.4 I4 i assume? what do the fuel trims look like? sounds like a vacuum leak
Yeah that's true about the fuel pump . My thoughts was if the revs are higher, it's pulling more fuel and stays running but when pressure drops for idle, it then starves from the lower pressure not sending enough fuel.

But that is probably not how it works now that I think of it more.

Vacuum leak it could be. I didn't get to take it apart yet, just side of the road diagnosis and then I drove it to her place about 2 miles just keeping the revs up
 

Lord Tin Foilhat

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can the scan tool you have do live data? check STFT and LTFT. they should be close to 0
No my regular scan tool didn't look like it did (or maybe I don't know how to use it lmao) but my Bluetooth odb2 might, I just didn't have it with me.

I'll be stopping by tomorrow to take another look at it when I have some tools
 

Lord Tin Foilhat

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Unplug the MAF and see what happens
So... Unplugged the MAF, car dies almost right away when trying to start. Plugged it back in...and now it is idling fine :dunno:

Did the same thing yesterday except didn't try to start it with it unplugged and that didn't do anything.
can the scan tool you have do live data? check STFT and LTFT. they should be close to 0
Here's the readout from my Bluetooth ODB when idling

Screenshot_2019-06-01-13-50-47.jpeg
 

Ron Vogel

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So... Unplugged the MAF, car dies almost right away when trying to start. Plugged it back in...and now it is idling fine :dunno:

Did the same thing yesterday except didn't try to start it with it unplugged and that didn't do anything.Here's the readout from my Bluetooth ODB when idling

View attachment 40254
Once the car is warmed up and idling , then unplug it. If it corrects the stalling, your MAF is bad. During cold start the computer relies on the O2 sensor only. It could also have an intermittent short. Tap test it by using a tap with the big end of a screwdriver. If it stalls/stumbles it’s got an issue.
 
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