The car, a 1989 with 72xxx easy miles, starts fine when cold ( not warmed up ). When warm it often will start with one or more cylinders not firing and will smooth out in 30 to 60 seconds. Sometimes it will not fire on enough cyls. to keep it running and a second or third try is necessary. It has experienced this trait for several years but getting worse. Dealer suspects injector leak down and suggests a new set. If I leave the key on for a few moments for the fuel pump to normalize befor cranking, it makes no difference. Someone have experience with this? I have tried Techron several times to no avail.

I have the exact same problem on my 92 190E 2.6 with 97K. I read a post on this site where someone said it could be leaky cold start valves. I haven't checked it out with a mechanic yet.
smk_texas

Sounds to me like it might be a faulty oxygen sensor or faulty heater in the sensor. On some cars the computer ignores the signals from the oxygen sensor during the first few minutes when the engine is started cold. This is because on some cars the oxygen sensor is not yet hot enough to function properly.

Maybe in your case the car runs fine when cold because the computer is ignoring the sensor. When the car warms some and the computer then recognizes the sensor, the miss returns to the engine because the sensor is sending incorrect signals.... untill the sensor gets good and hot at which time it begins to send normal signals to the computer and the engine will run fine.

But this is only one possibility. The diagnosis will take some trouble shooting. Defective temperature sending unit could also play a part.

Does not sound like cold start valve because the engine does start when cold.

Enjoy!

Smiles.

[Edited by ejsharp on 04-10-2001 at 11:09 PM]