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Old 11-06-2021, 05:26 PM   #1
DavePolyakov
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Default 3 inch exhaust, dies off throttle?

1990 740 Turbo with 15g + 3-inch downpipe and high flow catalytic converter. I will weld on the muffler when I have the time.

Since I've installed the exhaust the car will shut off when I let off the throttle and shift to neutral when in boost. It dies gently, as it would if you shut off the car normally. Rpm's drop to 800 then it shuts off.

At one point I had larger injectors and 012 AMM installed and I thought that was the issue. After going back to stock injectors and AMM the issue has persisted with no change. I've tried multiple different AMM's and no change. The only thing I've changed was the exhaust.

Anyone else experienced similar symptoms after installing 3-inch DP and exhaust?

Last edited by DavePolyakov; 11-06-2021 at 05:41 PM..
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Old 11-06-2021, 11:11 PM   #2
JohnLane
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Where is your O2 sensor in the exhaust? Makes a difference. 3” exhaust won’t make it stall. Everything in exhaust is aft of what does that. Have a good look at false air leaks and all basics that will make a car with an air mass meter stall.
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Old 11-07-2021, 01:16 AM   #3
ZVOLV
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Have you tried a battery disconnect? It can't hurt
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Old 11-07-2021, 12:43 PM   #4
dl242gt
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Are you sure the idle switch is working correctly? Another thought is the throttle plate closed all the way? It should be adjusted slightly open.
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Old 11-07-2021, 01:09 PM   #5
DavePolyakov
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I'm going to readjust the idle and see how it runs. I'm pretty sure it's idling low. That would make sense right?

I've done a battery disconnect and the o2 sensor is new and in the stock location.
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Old 11-07-2021, 05:16 PM   #6
JE Jr
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The sensor is new, but is it the correct Bosch one?
If some other aftermarket brand: Just ditch it.
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Old 11-07-2021, 08:51 PM   #7
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Maybe base idle is too low. Set to 500 rpm with halfway warmed up engine. Set it via the throttle stop screw and pinch the IAC hose closed. Then adjust TPS again. Solved the stalling of my 240 when coming of boost.
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Old 11-07-2021, 10:34 PM   #8
DavePolyakov
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Yep, the throttle linkage rod just needed a very fine adjustment, now the problem is gone! I found it easiest to adjust by leaving the car running and adjusting while it's on. It needed to be very exact or the car would keep stalling. I basically did trial and error.
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