Just thought I'd report back here considering it was this site where I got the information from. My Evo was dying turning into corners, or stopping at lights, anytime basically I'd decellerate to a stop. Much worse with clutch in. After cleaning out the idle valve, airflow meter body, finding a couple of broken wires to the air temp sensors, finding a distributor cap cracked in half it would hold a good idle not moving, and would restart first go. Only when moving would the car die, dropping to 450 ish then just dying. Most unnerving entering a roudabout or a tight corner to lose all power steering assistance. Anyway to cut a long story short, thanks to Steve Brothertons post on the OVP relay causing high resistance and a consequent voltage drop to the idle regulator I pullled the OVP tonight and lo and behold the problem has disappeared. I also saw 0 milliamps at the EHA. Removed the car feels great and no way does it stall no matter the abuse I give it. So hopefully once I get a new OVP everything will be a-ok. Thanks!

where is the ovp relay? i looked for the relay configuration on my 190e and couldn't find it. thanks, moneypit

On W124's, it is behind the battery.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".

can you describe it for me? any identifing marksS

Well mine is silver and is next to the ECU. It has a red top. There is a clear plastic cap over the red top which in my case contains two fuses. In front and to the left is a shorter black relay. This is the fuel pump relay. Both of these items don't look like a normal relay because they are so big.

Forgot to add, make sure you have warmed up the car before you remove the ovp (key out). The ovp controls the cold start valve you see. With no OVP I can't start my car from cold but I may have a really weak mixture - not sure. So don't drive around without the OVP it's there to do a job, just pull it to see if your problem goes away then get a new one.

I haven't looked at the cold-start valve circuit in awhile, but my impression is it does not rely on the ECU. It has a mechanical thermal valve that shuts off the valve when the engine heats up, and an electric heater coil that is turned on with the ignition - to speed up the process. Am I wrong?

Steve

I just want to clarify something nine months later..

My problem was not due to the fabled OVP relay. Rather I had an intermittant harness from the idle speed regulator to the connector block on the 4th intake runner. It took quite a while to find this as the problem would come and go, sometimes it went away for a couple of months at a time then I'd get a spate of cutouts, normally when the car was fully warmed up. I replaced the harness and the problem disappeared completely. I tested it by idling the car and wiggling the harness - bingo! I could never see open circuit with the multimeter which is weird.

Along the way I managed to replace the AFM due to a faulty potentiometer, that fixed a few flat spots etc.

Anyway thought I'd update this thread "for the archives"..