EHA valve - Mercedes-Benz Forum
 
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#1 (permalink) Old 09-27-2008, 11:49 AM
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EHA valve

I recently replaced the EHA valve(electromagnetic pressure actuator) on my 93 2.3 190 because of a small gas leak. With the new valve it seems to idle slightly lower and when you start it up cold, its slightly rougher and dos'nt seem to idle as high on the cold start cycle. Theres an adjustment on the back of the EHA valve. Anybody here fool with the adjustment before?....My car never was a high idler...but it seems on the edge of being too low now. thanks
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#2 (permalink) Old 09-27-2008, 11:53 AM
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Did you install a new O2 sensor? You should have a closed loop where the EHA will adjust according to feedback. Try not to mess with the idle/air/fuel mixture unless you have a scope to check out the duty cycle.
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#3 (permalink) Old 09-27-2008, 12:10 PM
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You have to check the lambda reading (mixture) now, will change after replacing EHA.
It's sounds like the mix is now lean, you need a MB test cable and a Fluke meter to perform this procedure. Abit risky but you can also remove the ball from the lambda tower and with a 3mm allen push down and turn a ever so lightly clockwise for rich and counterclockwise for lean. Just remember to turn extremly small amounts untill its idling smooth. Do a search for Lambda adjust and procedures. Oh, don't fool with the brass screw on the EHA!!!!
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#4 (permalink) Old 09-27-2008, 12:15 PM
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Just an EHA valve to rid of the morning smell of gas....Theres a plug on the back of the valve that has an adjustment screw in there. I'm not sure how important that adjustment is.
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#5 (permalink) Old 09-28-2008, 06:21 PM
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Review the thread "NO POWER"

If it is just idle control you should leave the EHA alone.

But if you feel the need to play.......

Any changes to the EHA differential pressure control must be minute.

1. Establish the current setting in such a way that you can get back to it.
2. only turn the adjustment 2-3 degrees at most.
NOTHING LIKE A QUARTER TURN!
3. After each adjustment reset idle control
Run Dyno
Run economy test
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#6 (permalink) Old 09-29-2008, 06:18 PM
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Thanks everybody and that "no power" thread. I need to put the old EHA back on to see if it clears up the problem,....but I took the screw out of the old EHA and played with the adjustment!.. Its hard to believe that that pressure device stays in adjustment, when that screw moves freely in and out. I would have thought it was spring loaded...but its not. I'll play with it tomorrow after work.Thanks
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#7 (permalink) Old 09-30-2008, 04:57 PM
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I put the old EHA back on and it would'nt run. That screw is touchy. I just put the new one back on and will see if I can get another EHA at a junk yard just to see if it makes a difference.
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#8 (permalink) Old 10-12-2008, 10:51 PM
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According to the web page maintained by Mercedes owner in Japan, he have disassembled several broken EHA's and found that there are two valve settings, one is 6 and 1/2 turns back from the end, and another is 5 and 3/4 turns. Just try both before buying new one.
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#9 (permalink) Old 10-13-2008, 06:03 AM
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Quote:
Originally Posted by kuwabaram View Post
According to the web page maintained by Mercedes owner in Japan, he have disassembled several broken EHA's and found that there are two valve settings, one is 6 and 1/2 turns back from the end, and another is 5 and 3/4 turns. Just try both before buying new one.
Thanks kuwabaram, that's good information.

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#10 (permalink) Old 03-31-2013, 12:22 PM
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EHA valve base setting

Quote:
Originally Posted by kuwabaram View Post
According to the web page maintained by Mercedes owner in Japan, he have disassembled several broken EHA's and found that there are two valve settings, one is 6 and 1/2 turns back from the end, and another is 5 and 3/4 turns. Just try both before buying new one.
Excellent information!
I made the mistake of trying an adjustment on my 230CE W124 coupe with KE Jetronic without noting its original setting. I found this post, tried the 5 3/4 turn adjustment, did not work; tried the 6 1/2 turn adjustment, and the car started and ran; a small adjustment of the mixture setting, and the car runs smoothly and with more power than before my ill-informed adjustment.
This is the only posting I have found this subject that gives us this important information!
For reasons unknown, all other information I have found on the basic adjustment is of no use, other than to warn us to not adjust the adjustment that we have already mistakenly adjusted.

Glenn
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