My 87 Rabbit convertible has developed an idle surge. It will run OK, then when warm and stopped at a traffic light, the RPM will drop to 500-700. Sometimes when releasing the clutch approaching a traffic light, the RPMs drop to zero and it stalls.
Both fuel pumps, fuel pump relay, fuel filter, and one other relay have all been replaced in the last 6 months.
TIA for any advice
Stats
I've had this problem off and on myself but have never really been able to find the cause. I always had a hunch that mine was due to some unmetered air leak that occurred when the car was warm. Its kind of hard to diagnose when it only occurs when you're in traffic miles from home. I'm not sure we have the same problem though because I believe that your car has an Idle stabilizer circuit that my 81 convertible doesn't. I'll be watching this thread anyway to see if someone else can come up with a solution.
Steve
Steve,
I finally went under the hood and got dirty to solve the idle problem. Several items seem to have contributed to my problem. I changed every (and I do mean every) vacuum hose and fitting I could get my hands on. Several of the plastic vacuum fittings had cracks that led to air leaks. Ditto for several hoses.... especially the ones coming off the fuel rail and the intake manifold. I used new hose clamps on every single hose end to tie things up and make it look nice. I also pulled every almost every electrical wire and connector and hit them with spray contact cleaner. Checked the main engine ground wires and cleaned and tightened everything.
The results were astounding. I am driving a different car. Idle speed is far more stable, acceleration is better, and my fuel mileage is up also. I hope this has really solved the problem for good. I plan to replace all 4 injector seals as well, but that's a few weeks off.
A little background info is also in order about my particular car.
1987 Cabriolet, purchased by me in March of 2002. According to the Carfax report and the fly-by-night used car dealer that I purchased the car from, it had sat unused for 18 months or so from late 2000 until shortly before I bought it. That time period took a toll on the rubber and plastic stuff under the hood as well as in the interior. In addition, the mechanic that I used until last month, did not know or understand this vintage of VW. I paid for his ignorance.On your car, check all the relays and fuses in the fuse box. My 87 fuse box is under the far left side of the dash near my left knee when I drive. According to my new (very experienced) VW only mechanic, the windshield seal leaks and water will drip down into the fuse box and corrode the contacts on the relays, fuses, and contacts in the fuse box itself. Very nasty to figure out if you don't know about it. 2 fixes......New windshield seal or a plastic supermarket shopping bag taped around the border of the fuse box to keep the moisture out.
Let me know how things work out for your VW and if my experience helped
Thanks
J>I've had this problem off and on myself but have never really been able to
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.