R50/53 Random bad idle fluctuation
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2nd Gear
Joined: Mar 2015
Posts: 108
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Random bad idle fluctuation
I have an 02 cooper s and I have an issue which almost always only occurs at the drive thru, when I move through the line once or twice, my car will start to stumble and then catch itself, and repeat a couple times and clear up. I have heard a load of times it is part of the ecu factory tune on the car. Well I just got it tuned today, and the problem actually got worse. Usually the idle will drop 1-2 hundred rpm, this time it dropped about 500 rpm, probably down to about 3-4 hundred rpm, it almost stalled but I gave it gas to recover it. It seems like getting on and off the gas quickly does something to cause this problem. So I’m pretty sure now it isn’t related to the ecu at all. Does anyone have any ideas what could cause this problem? I’ve replaced the pcv valve, the lines seem okay and aren’t collapsing. Could it be a map or tmap sensor? Any common vacuum leak areas? Any help would be great, thanks!
6th Gear
Joined: Nov 2004
Posts: 2,607
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From: Arnold, MO.
Common vacuum leak areas are, S/C boots, the hard vacuum lines to the S/C and the lines to the fuel regulator and BPV, pretty much all of them can succumb to heat related failures (cracking and drying)
As far as MAP or T-MAP, the T-MAP is that one that will effect idle most, and wear out quicker, but they usually go bad to the point it's extremely noticeable and not gradual at all.
But.... I still think you should be looking at the tune, contact the tuner and let them know the issue. If you just had it tuned and that changed something, don't overlook the obvious.
As far as MAP or T-MAP, the T-MAP is that one that will effect idle most, and wear out quicker, but they usually go bad to the point it's extremely noticeable and not gradual at all.
But.... I still think you should be looking at the tune, contact the tuner and let them know the issue. If you just had it tuned and that changed something, don't overlook the obvious.
Thread Starter
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2nd Gear
Joined: Mar 2015
Posts: 108
Likes: 5
Common vacuum leak areas are, S/C boots, the hard vacuum lines to the S/C and the lines to the fuel regulator and BPV, pretty much all of them can succumb to heat related failures (cracking and drying)
As far as MAP or T-MAP, the T-MAP is that one that will effect idle most, and wear out quicker, but they usually go bad to the point it's extremely noticeable and not gradual at all.
But.... I still think you should be looking at the tune, contact the tuner and let them know the issue. If you just had it tuned and that changed something, don't overlook the obvious.
As far as MAP or T-MAP, the T-MAP is that one that will effect idle most, and wear out quicker, but they usually go bad to the point it's extremely noticeable and not gradual at all.
But.... I still think you should be looking at the tune, contact the tuner and let them know the issue. If you just had it tuned and that changed something, don't overlook the obvious.
1st Gear
Joined: Sep 2014
Posts: 33
Likes: 3
Idle problems that look "random" are in fact related to canister purge.
When the ECU opens canister purge valve it closes a little more the throttle at the same time, because air and fuel are coming through the canister lines.
During that purge, if you have a little vacuum leak somewhere at the intake, the purge controller cannot regulate throttle opening properly which causes lambda oscillations.
Another reason could be bigger injectors without a proper injector scaling in the tune. Again during canister purge the ECU has hard time regulating lambda because injected fuel quantity is not as accurate as it should.
When the ECU opens canister purge valve it closes a little more the throttle at the same time, because air and fuel are coming through the canister lines.
During that purge, if you have a little vacuum leak somewhere at the intake, the purge controller cannot regulate throttle opening properly which causes lambda oscillations.
Another reason could be bigger injectors without a proper injector scaling in the tune. Again during canister purge the ECU has hard time regulating lambda because injected fuel quantity is not as accurate as it should.
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