98 Jetta 2.0 idle problems from A/C

[firstsacker]

One of my roommates has a 98 Jetta that is having problems when coming to a stop. If the a/c is running and you slow down to a stop, the car shuts off. It will start right back up, but the idle is significantly lower (between 200-300 rpms lower). I have replaced the plugs, wires, cap and rotor, but this did not help. When the a/c is not running, the car comes to a stop just fine. This only happens with the a/c running and the idle drops way down and the car shuts off. Has anyone else had this problem? Any help is greatly and always appreciated.

[Whit]

I have exact same problem. Did you ever figure it out?

[JettBlack313]

start examining AC parts (i have not had this happen so i am just trying here) check the belt tension and make sure the pulley on the AC turns easily that is all that i can think of.

[Whit]

Thanks. At this point don't think that's the problem. It's only when the A/C is on, but is intermittent -- sometimes ok with A/C on. When it occurs, idle speed drops about 200 rpm and is prone to dieing. Last codes were MAF, misfire on 2 of the cylinders and an over-speed on the rpm (not sure about that one but I have my suspicions). I've had the MAF replaced and replaced plugs & wires, but it did not correct it. After reading other threads, tried the spray mist test and detected some arcing at the coil. I'm going to try replacing that next.

It's a GLS, 2.0, 68K miles. I just got the car for my daughter from a used car dealer. The day after I bought it, had a reliable mechanic look over the car, and he recommended some minor fixes (brake pads); otherwise, deemed in good shape. Dealer has been cooperative, having the brakes fixed and also fixing the cruise control which knew wasn't working when we got it; even was kind enough to upgrade the stereo. He sent it to VW a couple times for the problem, but they couldn't find anything wrong. Took it back to the reliable mechanic who gave me the new codes (listed above) and replaced the MAF. I replaced the plugs & wires with OEM parts. It's a nice car and really want to get it right for my daughter who just graduated from college and will be going back for graduate degree and student teaching this fall. This is my first VW since owning a '57 Beatle back in highschool in the early 70's. Haven't kept up with the "new" VWs and have started wondering if this was a good choice.

[Whit]

Bummer. Replaced the coil, now it's a bit worse than before. Rough idle began as soon as I started the engine and turned on the AC. The count now is: new MAF, new plugs & wires, and new coil. :-(

[carla2988]

I know how you feel. This happened to me just yesterday. I have a 2001 VW Jetta 1.8t Wolfsburg ed. It has 69,000 miles. When ever I came to a stop or a slow corner, the car would just shut off. The only warning light that came on on the dash was the battery light. I had the a/c running as well while this was going on. What is the deal? However, quite surprisingly, the check engine light didn't come on. Now that is a miricale. I think my check engine light has been comming on since I bought it. This will be my last vw.

[boschmann]

Cleaning the throttle body & valve can sometimes help.

[Whit]

Took back to mechanic to rebaseline the settings. He found no communication with the throttle control module. Replaced, now everything is fine.
The problem wasn't discovered till the TMC settings were checked/read for rebaselining: could not communicate with the TMC. Hypothesis is this break in communication resulted in no codes being sent; thus, no code readings against the TMC. Just a clue for anyone having similar experience: if no codes show up on the TMC, try rebaselining.