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Old 01-06-2004, 11:26 AM
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Join Date: Jul 2000
Posts: 177
Unhappy Help me fix my high idle please: (I searched before posting)

Hello guys,
My 86 190E 2.3 8V is idle around 1100 when warming up in the morning, and then when hot around 15-1600. This is obviously to high. However, when driving and I put the clutch in to stop, the idle will randomly dip down to around 900 and then immediatlely rise back up to 1600. It doesn't seem to do this any other time. It's like the same effect you get from pushing down on the air flow adjust hole on top of the air box.

Things I have tried:
1. Checked the air flow sensor and one of the wires was actually disconnected from the connector, re-welded it and reconnected it to no change. WTF right?

2. Tried to adjust the air flow with the hex down through the air box hole. Can't get any results, I don't even know which way to turn to close the throttle more...

3. Messed with the throttle cable even though that shouldn't be the problem.

Things I think it may be??
The cold start sensor? It's like the dipping is the cold start wanting to lower the idle but then it comes back up?


Scott Chaffin
Homepage devoted to my 190E:
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Old 01-06-2004, 11:49 AM
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Join Date: Jul 2001
Location: SoCal
Posts: 1,303
The engine can't run without air, air control controls the engine speed. That is done at idle with mechanical restrictions and the idle control valve. The most likely causes of excess air are a throttle valve prevented from closing to the idle position (linkage problem) or an air leak bypassing the idle control valve.

Another possibility is the ECU increasing the idle control valve opening due to an excessively rich mixture.

'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7
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Old 01-07-2004, 10:26 PM
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Join Date: Jul 2000
Posts: 177
Thumbs up

The problem was easily solved. I had to push down on the valve and then turn the allen wrench right to lower the idle. Before I was just turning with out applying pressure. I was also able to resolve my gas pedal excess play by adjusting the throttle cable.
I should also add that it's easier to adjust the valve with the airbox off even though there is a hole ontop of the airbox. (My allen wrench wasn't long enough to press down with it on)
Scott Chaffin
Homepage devoted to my 190E:
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Old 01-08-2004, 02:53 PM
Registered User
Join Date: Oct 2002
Location: Toronto, Canada
Posts: 700
You should be aware of that the hole on top of the air box is for fuel/air mixture adjustment. Although it might have lowered your idle, it might have created a lot of new problems then solved the old ones.

Get a MM (multimeter) and check the lambda voltage, that will tell you where the mixture should be, if the high idle comes back, check for leaks in the vacuum system, most likely cause, then if all checks out, you can lower the idle with the knob on the idle control valve, at least on my 190, there are different versions of the same valve.


1985 190E 2.3L - a constant project.
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