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Old 05-18-2019, 05:27 PM   #1
snappymike
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Default Stalling issue

Car is a '91 740 Turbo.
Turbo was shot when I bought the car, replaced with a reclocked 15g.


Now, if I accelerate at 60-100% throttle and abruptly release the throttle, the car stalls. It does not matter if it's for 2 seconds from a stop and boost is 0 or if it is a 5 second pull on an on-ramp, the result is the same. It restarts normally after it stalls. It drives fine as long as I slowly raise the gas pedal after accelerating, I accelerate slowly, and I have no abrupt gas-->brake action.


Thoughts?

Last edited by snappymike; 05-20-2019 at 09:08 PM..
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Old 05-20-2019, 12:19 PM   #2
xDread92x
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Sounds like a possible air leak issue. I dealt with the same thing during deceleration in my 85 244. When you abruptly release the throttle, a heavy impact of air flow moves "in reversal". When i checked my intake hoses i found splits and/or deterioration etc. Replaced hoses and the issue when away. Car accelerated and decelerated much smoother.

Check hoses on intake hose from air filter to throttle body. Also check brake booster hose that goes to intake.

May not be a bad idea to check pcv while you are at it. If clogged up and junky it can make things run like sh**.
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Old 05-20-2019, 12:43 PM   #3
Dirty Rick
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If your system has an air flow meter and a boost dump valve the dump valve has to recirculate air back into the turbo inlet because that is measured air.
If measured air is dumped to the atmosphere the motor will go rich and likely stall.
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Old 05-20-2019, 09:09 PM   #4
snappymike
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Quote:
Originally Posted by Dirty Rick View Post
If your system has an air flow meter and a boost dump valve the dump valve has to recirculate air back into the turbo inlet because that is measured air.
If measured air is dumped to the atmosphere the motor will go rich and likely stall.
The 15g is still rocking the factory CBV, which looks to be in good shape.
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Old 05-20-2019, 09:11 PM   #5
snappymike
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The intercooler hoses are all new. My vacuum lines, brake booster, and IAC lines could use replacing though.
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Old 06-02-2019, 09:59 PM   #6
snappymike
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UPDATE!

Today I replaced the majority of the vacuum hoses. I inspected the rest. I inspected the PCV system, nothing gunked up hose wise but I did not remove the breather box. All the intercooler hoses are new and tight. IAC looks clean. Still stalls when I leave off the throttle abruptly when in boost.

I also swapped out the MAF sensor for the one from my well running 240 and no difference.

I sprayed soapy water everywhere while running... Nothing. I sprayed ether everywhere while running... Nothing.

Any ideas?


Any ideas?
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Old 06-03-2019, 06:30 PM   #7
esmth
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i had a similar issue right after i +t'd my car. It turned out to be the throttlebody/TPS needed an adjustment. https://www.brickboard.com/FAQ/700-9...itchAdjustment
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