possible boost leak causing high idle

[Trbogrl]

Hi, this is my first post so bear with me. I have a 95 TSI awd with a 19c turbo, FMIC, and 3" turbo back exhaust. after putting the turbo on and tuning my s AFC, i noticed that my car was idling really high, like at 1400. I tightened the idle adjustment screw on my throttle body and got the idle back down to where it should be, but now when i have abrupt RPM changes my car acts like it's gonna stall and has stalled once. First of all, was it bad to mess with that screw? And also, I was told that a boost leak could cause my car to idle high, and if that's true, how can I check for one?

thanks,
Laura

 

[L2RTSiAWD]

What is your 1000rpm low setting on the AFC?

 

[Vindawg]

if you have a boost leak you would hear a gargaling or like something is flapping in the breeze under boost pressure. You would feel a noticable loss of power, when i had a boost leak it turns out i didn't tighten the top ic hose, you should check all the hoses that are turbo related, that really didn't give me a high idle though. you should check your vacuum hoses, i had one out and caused my idle to shoot up to 2500 rpm.

 

[dave2953]

Boost leaks don't cause high idle as far as I know. If you had a boost leak your car would bog down at mid to high rpm. There would be too much fuel as a result of the lost air. I think the screw you are talking about is the BISS, and there are several posts about that subject. Like the person above me said, check all the I/C hoses, intake pipe, etc. Doubtful that a boost leak is causing the problem, Sound more like a vacuum leak. That can easily cause a car to idle high.

 

[LaserRST]

The BISS adjustment can only properly be adjusted when the ecu is out of the picture. A service manual will tell you how to properly adjust the idle without the ECU. The same thing goes for you Timing. Reason being is that the ecu always controls how the vehicle idles and will (I love this part about DSMs) learn you vehicles adjustments and remember it through some fuzzy logic type of hardware or programming. This is designed to monitor, adjust, and maintain performance and economy. Gotta love a 250hp car that still gits 28-30mpg. This is why you were able to adjust it fine in the garage but on the road its a different story. I would maintain stock boost levels and set the afc to stock settings (i believe thats 0% across the board). Then do the proper jumping and grounding you need to do, readjust your BISS and slowly make your adjustments with your AFC and your turbo. My guess the initial problem sounds like the AFC, more so than boost leaks.

 

[doug]

Originally posted by LaserRST
The BISS adjustment can only properly be adjusted when the ecu is out of the picture. A service manual will tell you how to properly adjust the idle without the ECU.

This is good advice. There's also a VFAQ on how to adjust base idle at VFAQ.com. Unfortunately, there's more to it on a 2G than just adjusting the screw.

 

[Trbogrl]

thanks, guys, I chcecked all my intercooler pipes and I did have a leak at one of the connections. I ordered a better connector wrapped it with some of that heat insulating stuff because I think the high temp near my exhaust manifold caused it to become weak. So far it seems to be holding alright... now if I could just stop blowing up the O rings inside my injectors I'd be in pretty good shape...