hey,
Ive got a 91 TT auto with ud pulley, catback, and pop charger. When my car is all warmed up it idles around 700rpm, but while im waiting at a light the revs will drop to 500 or 550rpm, and then just jump back up to 700rpm. Whats the deal with that?
jon

 

im sure somebody knows whats up. otherwise im giving up and taking it to my mechanic.
jon

 

actually, my car wouldnt start, the starter relay was loose! weird or what. so i yanked it. messed with it and stuck it back in. naturally, the car starts fine now. well anyways, i wondered if anything else was loose. I spent an hour or two and guess what, the wire going to the #3 cylinder was loose. I guess that when it jiggled out, the cylinder stopped, and then it ran rough, and jiggled in. crazy eh??? oh well, it all works now. If i can figure out why it's running so rich, i'll be in great shape!
jon

 

My '92NA had some idling trouble as well. It used to stall every-now-and-again for no reason, and I found if I removed the ign relay and put it back in it ran fine, until....
It just died as I was driving along, it never did this before, it only stalled at idle, so I removed the relay and put it back in, nothing, still no start. Towed it to my mechanic, who thought it may be a faulty ignition amp, but no. After 3 DAYS trying to track down the problem, he found a broken plug waaaaaay in the middle of a loom somewhere that was corroded and arcing between pins. He replaced it and after $NZ900 (600 of which is labour) work the car runs like new, it even improved it's throttle response and it pulls better from low RPM.
This is and uncommon cause, ignition amp is very common, but it may help.