Questions and Answers

Volkswagen Jetta Idle Blub Q. The car blubs really bad in the summer when the A/C is on. The idle drops really low then goes back up, and then down again. When I slow down and push in the clutch the car will also often die. It would seem that it is worse on hotter days. I found this out by using the A/C at night, with no problems. Then using during the day, the problem still persisted. Any ideas? 1998 Volkswagen Jetta 2.0 liter 4 cylinder Manual transmission 103,000 miles Fuel Injected Cruise Control, P/S, A/C Cheers!!! Alex

A. The A/C relay is supposed to send a signal to the Powertrain Control Module (PCM) to let it know the A/C is on and that it should raise the idle to compensate for the added load. It may not be doing this or the PCM is not responding to that signal.

Another possibility is the Idle Air Control Valve (IACV) is not opening enough to allow enough air to compensate for the added load. A good cleaning of the throttle body and IACV would probably be the best thing to do. Quite often that in itself cures many idle speed problems.