I have a 1991 300E2.6 that has some intermittent, erratic power surges and losses. They occur at any time; idle, accelerating or cruising. It seemed like the fuel/air ratio was changing rapidly but, it only lasts for a few seconds.

Following a few posts from here I changed the over-voltage relay and the Electro-Hydraulic Actuator (EHA) but the problem remains. I disconnected the EHA and the car runs fine. No power surges or power losses; just harder to start when it's cold.

I'm guessing that I'm getting a power spike that causes the EHA to fluctuate and thus fluctuate the Fuel/Air ratio.!?!?!?! Where should I start next? The MAS control or the alternator or WHERE????????

Intruder

That car has a cold start valve,(104 070 00 46) have you thought of that maybe? I would ask one of the techs I'm just guessing since I sell a lot of them!

Or maybe even the fuel pressure regulator (000 078 03 92) bosch number 0 438 161 001 also availble on the fastlane catalog http://www.peachparts.com/catalog

Thanks DR Parts. I'm guessing its not the cold start valve since the car varies between lean and rich, whereas a faulty cold start valve would cause rich-only problems. Am I right??

The fuel pressure and flow is steady and within spec.

But, the problem resolves when I disconnect the EHA (I would expect a hard, cold start with it disconnected)

BE SURE THAT THE OVERVOLTAGE RELAY IS NEW!!!! IT WILL CAUSE THESE PROBLEMS.