Steve J.

My '87 S4 can achieve 135mph very quickly and smoothly with plenty of power but then just levels off and sings along happily, accelerator on the floor. 135mph is way faster than I need to go but I am concerned that all is not right. The car seems to be running fine, so before getting into clogged cats, slipping torque converter, etc. I'm thinking maybe it's as simple as not being able to apply full throttle. From idle there is a lot of pedal travel (maybe 10-20%) before engine RPM's increase, unlike the two earlier 16V 928's I have owned. And there seems to be a LOT of slack in the accelerator cable at the engine at idle position. Manuals are not very clear on cable adustment. How much slack should there be in the throttle cable and other cables at the engine and how are they adjusted?

WallyP

1) Carefully inspect the throttle pedal. There are two sets of mounting holes, so you can change the pedal position. Make sure that you have full travel, and that there is no interference with pedal travel. If you have an automatic, make sure that you can depress the kick-down switch with the pedal.
2) Carefully check the cable from the cable quadrant (the mechanism where all the cable connect on the engine) to the actual throttle. On S4 cars and up, there is a pulley at the rear of the engine. Make sure that the cable is properly routed around the pulley.
3) Adjust the throttle pedal cable to the point that it almost, but not quite, moves the cable to the throttle. With the engine idling, pull slightly on the throttle pedal cable at the quadrant. If it is correct, you can feel just barely perceptible slack before the idle speed increases.
4) Do the same with the transmission cable (automatics only).
5) The cruise control cable should have a little more slack than the others.

When the cables are correct, you should have full throttle before the kick-down switch operates (automatics only), and the transmission should shift at the correct speeds.