I have a 84 190D 2.2 and the idle has gotten rough since the weather has turned cold. Before the weather was cold the idle was fine, would the weather cause this? Does this car have a high idle feature? The motor is shaking. Should I just turn up the idle ?

rough idle at what times? startup or after driving? only when cold?
you could have a bad glow plug, weak lifters (any rattling?) worn injectors, or even out of time.
an air leak in the fuel line is the 2nd most common cause of bad idle, first would be glow plugs on startup...

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1987 190D 2.5Turbo
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Sorry, its all the time now. Why would it do it all of a sudden?

Did you install an IP with an electrical gizmo on the back? Is there a disk-shaped object on the back of the IP that has a vacuum fitting ?

Start reading about ELR, EDS, electronic diesel system, idle control and re-examine the vacuum routing for your engine. There are vacuum valves that are temperature based and have a great effect on idle.

Is this IP new to you?

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Its a bad motor mount.

Well, changed one motor mount and the tranny mount and it is still rough. Going to change the other motor mount and see if that helps.

Is this the engine that you replaced the head on? and rebuilt?

Which IP did you use?

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Yes,thats the one. I had a choice of three (injector pump), I chose the one that was on the motor that was in the car when I bought it. The other pump was sitting outside with one injector line off, the other one was the one that you sold me.

If you find that the idle speed is the problem, it is adjustable.


On the back of the IP (facing the firewall), at the top is a disk with a vacuum line. Loosen the locknut and turn the disk.


There is a cold idle feature that is engine temperature-based and uses a vacuum signal sent to that disk on the back of the IP.

Good luck. Don't forget the usual suspects (air ingress, bad fuel... etc...)

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I allready adjusted the idle once before, but might do it again. The cold idle feature works but it only works for a very short time. Is there something I can do about that?

My solution was to remove all that 'stuff' and raise the idle to a setting that was reasonable on cold starts, but not too high when the engine was at full temp.


If you can verify that all the vacuum fittings are in good order along with the solenoid and thermo switches... then its probably the control unit / relay.

That would make the most sense considering your symptoms : initially works, but fades out of function

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