I have a 1993 300E 3.2 M104 engine that recently started acting up on me. When I start the car cold, it starts and idles fine but after about a minute or 2 the idle races and cycles between 5K-15K RPM cycling in 1 or 2 second intervals then the idle becomes rough and the engine eventually stalls after 5 seconds of rough idle. Then when I restart the engine, I get a rough idle then it stalls immediately. Here is what I have done to try and correct or diagnose the problem so far:
- checked fuel pump relay (fine)
- fuel pump noise is audible when ignition is turned on
- checked spark plug (strong spark detected during crank)
- replaced OVP (did not solve the problem)
- visually inspected vacumm hoses within engine compartment (all's fine)
- the car is still sitting in my garage - undriveable...
If anyone can help with suggestions with my diagnosis, i'll appreciate any input. Thanks in advance.