A strange phenomena.

The engine starts with as normal, but as soon as you press the gas pedal and reach about 1500 rpm the engine dies of cuts out. If you drive the car it can not go beyond this rpm.


This can drive you crazy... but what happened?

Well, the Idle switch has not opened when the gas pedal is pressed. The LH thinks that it is in idle position and runs the idle program. Fine.

When it sees the engine speed over 1400 rpm it "thinks" we are still driving (coasting)  and have taken the foot off the gas to roll the car to a halt.

So it cuts fuel like it is designed to do.... even if you press the pedal to increase rpm and drive faster, while the idle contact tells the LH that it's time to cut fuel to reduce rpm to idle level (650-750 or so) 

The car obviously becomes hard to drive :)

This fault is recorded in the LH ecu as "idle speed contact (ohm) short to ground", DTC 12.


Theo Jenniskens

1992 Porsche 928 GTS, Midnight Blue