Own a 1991 300E 2.6L at 128,000 and have been having problems with shuttering and stalling at idle. I have gotten the coil, plugs and wiring replaced along with fuel injector treatment from the tech guys with no success. The guys at the shop think it is a coolant leak in cylinder 6 through the head gasket but the more I read the more I think it may be something fuel related. What do you guys think I am going to check to OVP to see if the fuse has blown and will get back but wanted to see if I could get feedback beforehand. Thanks!!

One note. At idle I'm at 500 rpm or below and have always thought this is a little low. Is the norm 750?? Should I increase the throttle to try and solve the problem??

Has the rotor/cap ever been changed under your ownership? These cars burn through caps/rotors faster than any other car I have owned. Checking/changing the OVP is also a good plan. Head gasket causing this issue is highly unlikely IMO.

It's supposed to idle smooth as glass at ~400rpm. 750rpm would be considered a "high idle"...there's no idle speed adjustment either.

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1991 300E - 212K and rising fast...

Thanks for the quick reply JohnM. I just checked the OVP fuse and its good. The recent work replaced the distributor cap, rotor, wiring and plugs because the engine would not start at all. These fixes cured the ignition problem but the shuttering problem wasn't cured. After these problems still occurred after $700, the tech said that the cap was faulty and replaced it under warranty in addtion to a fuel injection cleaning. I appreciate all the help!!

OK. More than likely culprit(s) are the CPS (Crank Position Sensor), or the EZ-L Ignition Module (Black) on the driver side of engine bay. Both should be testable by your mechanic.

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http://i193.photobucket.com/albums/z...-RESIZED-1.jpg
1991 300E - 212K and rising fast...