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What could be casing this? I'm at a loss.

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3.8l idle
1K views 3 replies 2 participants last post by  NavyVet 
#1 ·
I took a video of my car's issues when I go from being on the gas to letting it idle.

https://youtu.be/1lthBKn1eYU

It does this same thing while I'm driving. Notice the lights dim and the oil pressure drops slightly. It idles low too. Between 500 and 600 RPM. I've replaced the MAF sensor, air filter, and PCV valve. There was a little bit of oil in the throttle body but that was before I replaced the PCV valve. When I'm warming the car up when it is below about 45 degrees it likes to stall when I press in the clutch while driving until it is up to running temperature. To initially get it to start I have to hold the gas at about 2000 RPM until the engine is warm. Even then if I have to shut it off and restart it I have to drive a while before it won't stall when I push the clutch. I have gotten two codes before when this happens but it is somewhat rare. They are P0172 and P0175. If I unplug the MAF it fixes the stalling issue and makes the issue in the video slightly better but it's definitely still there. Does anyone have a solution? The throttle position sensor at the manifold seems to be working. Idle is at 6.7%. The MAF reads 7.7 g/s. Intake psi is steady at right around 5 psi. Vacuum is at 19.9 in/Hg. If you have any ideas please let me know. This has been going on for the last year and a half. I've had to drive around with the MAF unplugged and suffer from poor gas mileage even when it's plugged in and kind of working. I also don't experience any of these issues in the summer when it's warm.
 
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#2 ·
P0172 and P0157 are fuel trim system rich banks 1 and 2.
Probably comes from the MAF being disconnected.
Have you cleaned or replace the Idle Air Control valve, it will cause the issues you're having
 
#3 ·
It's a drive by wire throttle system so it is my understanding that the idle air control valve doesn't exist on these cars. I believe that's because the throttle plate controls idle with the servo motors. Also I only get P0175 and P0172 when the MAF sensor is connected. If I disconnect it the only code I get is the one telling me the MAF is disconnected.
 
#4 ·
It's a drive by wire throttle system so it is my understanding that the idle air control valve doesn't exist on these cars. I believe that's because the throttle plate controls idle with the servo motors. Also I only get P0175 and P0172 when the MAF sensor is connected. If I disconnect it the only code I get is the one telling me the MAF is disconnected.
You are correct. So it's either the throttle positioner or the unit on the gas pedal.
 
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