Update: so I did replace the EHA. I do not have any problem with acceleration after doing that. However, I still have a rough idle.

I haven't done anything with the OVP.

I've also heard there is some adjustment that can be made to the EHA? I haven't done anything with that. Could have that anything to do with the idle?

BTW, after new plugs, wires, fuel filter and O2 sensor I'm getting noticeably better mileage.

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Ty H.
'87 300E 135K Miles

You can adjust the EHA via a small screw in the rear. MARK THE ORIGINAL POSITION.
Without use of a fuel pressure gauge you have no way to correctly adjust it. Mark the original position and give it turns in 1/8th's.
FYI Though: I HIGHLY doubt that is the cause of the rough idle though. Look at vacuum leaks at the idle control valve.

What does your economy gauge show at idle? Where is it at? Does it fluctuate at all?

Does the engine smooth out in neutral? Condition of motor mounts?
Is your ABS light illuminated? (OVP failure symptom)

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

PS2CHO,

My daughter has an '87 300E with an economy gauge. I have a '91 without. When I was checking her idle out tonight, I noticed that the economy gauge stays in the middle during non-geared idle and she says it always goes into the red when she drives it (my car use to idle like hers but I replaced everything and now it is smooth in gear or out). I recall reading that the gauge should be hanging out in the black zone most of the time....no? So, I was thinking today that I will replace the 02 sensor, water temp sensor, replace her Idle Valve hoses, as well as cleaning the valve out too. Anything else I can check or look at? Anyway, she wants to sell it and buy a Scion but I want to get it running very good b4.

Thanks,

Steve