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Registered
1989 w126 300se
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23 Posts
Discussion Starter #1
The car starts up and runs fine when cold open loop. Soon as it warms up idle lowers a bit and fluctuates. If in park it idles fine. When I am driving and its warm( closed loop) and I am coasting to a stop it idles real low and then stalls. If I was to be applying the brake harder it wouldnt stall. When switching from park to drive once warmed up it wants to stall. If it doesnt stall at a light when I let go of the brake most of the time it just creeps forward without the stalling. Also wants to stall in reverse and surges a bit so I end up reversing faster than I would like to keep it going and then hitting the brake to keep it from stalling. I look like a a$$hole.
 

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Outstanding Contributor
1989 560SEC, 1989 560SEL, 1995 E420
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4,086 Posts
Don't know the answer but you might want to unplug the EHA after you reach closed loop and the symptoms start to see if they clear up. If they do, I think you'll want to be testing the electrical side of the system. Lots of good info in the manual and a troubleshooting chart in section 073-121.

Easy and tempting to start throwing parts at this sort of problem. If you have spares, I'd sure try it. But there's no good substitute for diagnosis.
 

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Registered
1989 w126 300se
Joined
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23 Posts
Discussion Starter #3
Don't know the answer but you might want to unplug the EHA after you reach closed loop and the symptoms start to see if they clear up. If they do, I think you'll want to be testing the electrical side of the system. Lots of good info in the manual and a troubleshooting chart in section 073-121.

Easy and tempting to start throwing parts at this sort of problem. If you have spares, I'd sure try it. But there's no good substitute for diagnosis.
Can I drive it with the EHA disconnected? It will sit and idle all day long. It's just when I am coasting to a stop or around a corner at low speed it will start dropping RPMs and slight shuddering and surging then probably stall out. It's so slight it's done it and I didnt know until I tried turning wheel or put pedal down and nothing.
 

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W201 Moderator
89 190E2.6- 5-speed Manual, 95 E320 Sportsline-sold, 2001 E320 4matic Wagon-sold
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2,619 Posts
Stalls of this sort are generally OVP related. If the car runs fine except it stalls coming to a stop "randomly" then look no further than the OVP. Been there done that and took "us" 4 months to find the problem.

Do not replace it, pull it and check the date code. It will have the production year and month, or year and work week printed on it. Let us know what it says.

I have not witnessed an EHA causing stalls in idle or going into idle. Pulling it would cause the idle to go up "generally" which may prevent stalls as the ECU will no longer control idle speed in a regular fashion.

I would not recommend driving around with the EHA connector removed. Removing the IACV temporarily should be OK since all you are doing is raising your idle speed and wasting some gas but it will not effect the air/fuel mixture, at least in theory.

- Cheers!
 
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