Musche

Here's the problem- the 89 turbo starts and runs great when cold. It seems to be running a bit rich since I notice a good bit a black carbon soot at the tailpipe. Haven't taken the plugs out yet but I assume they will be black as well. However, when the car is hot, it starts fine but stumbles for about 10 seconds then runs fine. I have to hold the throttle down a little bit to keep it running at about 2K rpm and hold it steady. After the 10 seconds or so the rpm jumps up about 500 rpm and all is well. The car has had the O2 sensor replaced by the PO with a splice to the original connector. Any expert opinions about a fix are appreciated.

testarossa_td

Here is my two cents. Possibly the O2 cheap enough to replace to make sure it is not. Next in line TPS
Could be spark plug, wires, cap, rotor.
Do a search others experiences might help you. Search under my profile for posts started by me...TPS a long story.

Musche

Any other ideas? Already have a new cap and rotor installed. I'm still thinking is a time differential between when the sensor heats up and the readings the DME gets from the temperature sensor.