I have a 1991 240 with 140,000 miles. It has started running rough - rough idle, almost to the point of stalling, lacks power on acceleration - but only occasionally. It doesn't seem to matter whether it is cold or hot, and the condition just "happens" - whether at idle or driving. Most of the time it runs fine.

I cleaned the throttle body, replaced the flame trap - which was fairly clean anyway - and put in a new K&N air filter. Got a 113 fuel injector fault for the first time. It idled rough. I looked for vacuum leaks, and lightly nudged the injectors. The idling smoothed after just touching one injector - third from the rear. I Cleared the code, and all was well till this morning. I idled while dropping my daughter at school, and the roughness returned as soon as I pulled from the curb. No repeat code yet.

Any ideas? The 02 sensor was new last year - 15000 miles ago. The fuel filter was replaced about 20000 miles ago. I had a new tank put in recently - we moved and the shipper dented the original slightly when the car was offloaded.

Thanks for the help.

David