Rough idle/hesitation after EHA adjustment (W124 300E)
 

History: My '86 300E developed a warm-start difficulty about year ago. The problem persisted despite changing the plugs, cap & rotor, wires and air filter.
About 1 month ago, I decided adjust the EHA per the instructions on this forum. I may have inadvertently turned the adjustment screw too far before realizing that my screwdriver was, in fact, seated in the screw head, and the screw turned with very little effort. Having lost my point of reference, I gave the screw a partial turn in the opposite direction to try to 'undo' my possible overcorrection.
After my attempt to adjust the EHA, my car sat for 1 month until last weekend, when I was able to charge the battery and start the car.
The car started just fine, but now has an uneven idle. The engine stutters severly until the RPMs exceed about 3K; then it smooths out. It's practically undriveable. Even when the car is warm, there is a pervasive gasolene odor in the exhaust... too rich?
Could this be a result of a misadjusted EHA? If so, which direction should I turn the adjustment screw to remedy the problem?
Thanks!
Mika

You have to measure and adjust, if required, the base mixture using the proper procedure with a multimeter that has a duty cycle function.

www.landiss.com/mixture.htm

Duke

Just to double check here, but did you remove the screw to get to the tiny hex bolt? The screw doesn't do the adjusting, it just covers the hex bolt (small, 2.5m if I remember correctly).

Jonathan

Yes, I definitely removed the cover to expose the 2mm hex adjustment screw. I thought my driver wasn't seating properly because I felt almost no resistance as I turned it. Then I looked more closely and realized that I had been turning the screw all along. Oops...
Mika

That's it, all right. Your description sounds like it's lean, but a multimeter with duty cycle will tell the real story, as Duke says.

Lots of info available in a search, including links to good descriptions of the system. Try a search on "adjusting the EHA". It was my first stab at it & lots of people chimed in with excellent advice. :cool:

HTH,

in trying to experiment on possible solutions for rough idle and cold start issues on my 91 560SEL, I found that adjusting the set screw in the EHA affects the 2500RPM behaviour mostly with very little change in the IDLE behavour. The opposite is true with the set screw in the mixture Tower.
Adjusting the mixture in the Tower affects IDLE behaviour mostly, with very little change in the 2500RPM behaviour.

Going back to your original issue of warm-start difficulty, a lot of postings point to the fuel accumulator as a probable cause.