Mongo

Whiskey. Tango. Foxtrot.

I adjusted my kickdown cable a little tighter (since it wasn't kicking down properly) today and went for a cruise trying to duplicate the same symptoms of the surging or bucking. At cruise, it's smooth now. I haven't disconnected the battery yet, and it may be luck, but somehow, I'm developing a theory that the tension from the kickdown cable is causing the throttle to close completely now after lifting off the gas. Before, I would feather the throttle at cruise to maintain speed and it would buck and surge. The TPS is only 2 years old in this car, but I am thinking that it could be sticking???

porschemarine

Hi,
I'm new to the forum, but not new to 928 ownership (I've had mine for 7 years), and it sounds like I have the exact same problem. I have an '88 5-speed, and no matter what I do to remedy this surging problem it returns. I hope you have luck finding a lasting solution, because I'm running out of parts that haven't already been replaced (I know, hard to believe)

dcrasta

Vacuum lines?
Grounds?

Mongo

Small Update. My car's problems seem to have cured itself. This could have been related to an O2 loop issue. Car runs fine now at cruise with zero surging and skipping. However, the idle RPM still worries me since the tach sometimes shows 500 now, but the car seems like it's idling normal. Probably a false reading on the tach considering the age of the instruments. It does have a slight stumble on take-off at times. Also, I have begun to notice that when coming to a stop, my transmission takes awhile to downshift, causing the engine to drop below idling threshold. Aside from those issues, I really have no complaints. Did an oil change on it last weekend and dropped two pints of Marvel Mystery Oil to cure some noisy lifters...

AO

Doubtful...

What was this? Are you running open loop now?

Mongo

No. I'm still running closed loop, but I have tried to duplicate the situation several times with no success. Before, I could just be driving the car at 65-70 and it would start surging. After a week, it's gone. Between that period of time, new sparkplugs were put in, and I checked all of the ignition wire connections. I used electrical contact cleaner on the ends for the cap and a very thin spread of di-electric grease over the terminals. Those wire ends though looked 'fine' visually prior to cleaning. I also re-arranged the ignition wires as well since I did find two wires crossing over eachother. The sheathing looked good on both though, so I highly doubt the spark was jumping on them. However, whatever I did has not caused the issue to come back.