Malibu Start and stall

John Diagnostician Butler, Pennsylvania Posted   Latest  
Question
Driveability
2011 Chevrolet Malibu LS 2.4L (1 LE5) 6-spd (6T40)
Start-Stalling

Car starts and then immediately stalls (no security light) Fuel pressure is 60psi at all times. When I unplug the intake cam sensor it runs fine, don't stall. I scoped the intake sensor and noticed that it only pulls down to 700 millivolt so I thought that was a problem, I had the shop put a new intake cam sensor in and still the same problem and voltage. I got a known good waveform and it is 790 millivolt, I compared the 2 waveforms and the intake is retarded 2 deg and exhaust was 11 deg retarded compared to the known good. At the time of the capture the car stayed running for some reason. I cant see the exhaust cam being off 11 deg stalling the engine, I have seen them off quit a bit more with no stalling issues. There are no codes. Thanks..

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Rusty Owner/Technician
Oakham, Massachusetts
Rusty Default
   

If you unplug the phaser actuator solenoids, will it idle normally? if it’ll stay running, look at the cam position error (variation) on a scan tool to see what the PCM thinks.

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John Diagnostician
Butler, Pennsylvania
John Default
 

I forgot to unplug the phasers. I did look at the variation and when it was running it was fluctuating about 2 deg from desired. When it wouldn't run I couldn't really get any useful data because soon as my scanner started responding it shut off

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Rusty Owner/Technician
Oakham, Massachusetts
Rusty Default
 

I think exhaust timing that’s 11 degrees late would be like an EGR valve stuck open and will cause an idle stall. I had a KIA that acted this way at a hot idle. It didn’t get repaired as it was a dealer‘s car and went back to auction after I discovered that the issue was internal. I theorized that there had to be an internal oil leak across one of the phaser passages that allowed some oil

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Scott Owner/Technician
Brantford, Ontario
Scott Default
 

Is it possible you are putting this into s fail safe when you unplug the sensor? can you grab some scan data , graph and see if there is any abnormalities during the event ,

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John Diagnostician
Butler, Pennsylvania
John Default
 

I am willing to try anything, what data would you like me to graph? I have the cam crank correlation but when I was able to capture this the engine mysteriously started to run and not shut right off after start up, and as of last night its still running with no problems. I was thinking maybe the phaser or the solenoid was sticking and advancing/retarding the cams as soon as the engine fired up

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Jerome Owner/Technician
Modesto, California
Jerome Default
 

Typically folks post the know good cam/crank correlation with phasers unplugged mabe that's why you have the 11° swing on the exhaust cam, what's the 5 volt ref doing? Food for thought 5 volt refs can be internally shared on the voltage converter inside the pcm, dont let the wiring diagram fool ya.

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