throttle switch acting weird

[MARCANNEKE]

Hi there,

I've been struggling with my 2.0 D-jetronic engine for a while. It backfires when releasing the throttle pedal, and the idle is very unstable. When I disconnect the throttle switch from the system ( unplug it), the idle is suddenly stable but rises about 200 rpm, and my engine runs smoothly without backfiring!
Could the switch be the devil inside my D-jetronic, or should this observation be an indication for other problems?
Thank You in advance for any replies.

Marc
Belgium

[beatnavy]

Hi Marc - This site: D-Jet Troubleshooting can help a lot. Tons of good info on D-Jet here on all the pages.

I would check the TPS Board for wear on the tracks and recalibrate it. I would test the MPS with a vacuum tester. I would look all over for vacuum leaks on the hoses.

Before anything, however, are you sure your car's in basic tune (valve clearance, dwell, timing)?

Also, does the backfiring and unstable idle occur when the car is warm or primarily cold/warming-up?

[MARCANNEKE]

Hi Beatnavy,

Backfiring only when warm. Also a little "bucking" while warm.

Greetz,

Marc

[beatnavy]

Hi Marc,

Lots of variables, including some I already mentioned. You can try installing a new TPS board (here's an option from 914Rubber). Otherwise, I would start trying to eliminate those variables (vacuum leaks, exhaust leaks, MPS, valve clearance/dwell, and timing).

rc

[TheCabinetmaker]

make sure the throttle switch is calibrated, it can be rotated tot eh correct position to make sure in the idle position it is truely all the way off.