Could someone tell me what could be causing the high idle problem.When I first start the car up,everything is fine.Once I give it gas the idle rises and falls.It goes as high as 2 grand and may come down to 1000, which is still to high.I changed the plugs ,air filter,Fuel filter,Cap and rotor and still the problem persists. I sprayed carb cleaner around the intake manifold to check for leaks and there was no change in the idle while doing this.Is there some kind of sensor that could be causing this.Any help would be appreciated.

Thanks
Mike Bittner
91 190e
96 C280
94 Range rover
69 camaro

Do a search for idle control valve.

Is there a way to test the IAC valve.A new one is kinda pricey.

With all the idle problems we had, the two that seemed to most effect an intermittant high idle were the OVP (bad internal joints) and idle air leaks. What caused a fluctuating idle (rev up then slow down) was a worn airflow meter potentiomenter. Possibly sluggish idle control improved by cleaning the ICV.

In any event, replacing all the hardened, cracking, idle circuit rubber hoses and the lower airflow meter plenum, repairing the solder joints in the OVP, then replacing and adjusting the airflow meter pot, cleaning the ICV - this all ended leaving the idle about perfect for several years now. Expense was low, labor a bit involved.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7

Do you have to remove the intake manifold to get to all the idle circuit hoses.Could someone tell me what the metallic box is below the intake manifold that is connected to the throttle butterfly linkage.

I think you are describing the cruise control actuator.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7

You are correct about the cruise.I can see that the unit is made by VDO.

Thanks

Don't replace it, YET, just take it out and clean it with some aerosol parts cleaner. Check all the hoses leading from and to it for leaks or clogs. Put it back together and see if that helps. The ICV is between the 3rd and 4th intake.

Do you have hard starts? The only other sensor that will affect idle that was not mentioned yet is the Water Temp Sensor. If it is bad and the CIS-E ECU thinks the engine is colder than it actually is then the EHA wil enrich mixture and the ICV will increase Idle Speed. Another one that will cause higher idles is the Switch on the throttle linkage that lets the CIS-E know that the throttle is closed and your foot is off the gas. That drops idle to the 750 mark. Also of course any vacuum leak as stated will cause the idle to raise. Also check the Intake Boot. It is under the AFM between the AFM and the Throttle Body, when craked it allows excess air to bypass the AFM plate and not be metered and raises idle, also would cause hard cold and warm starts.

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~Jamie
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2003 Pewter C230K SC C1, C4, C5, C7, heated seats, CD Changer, and 6 Speed. ContiExtremes on the C7's.

1986 190E 2.3 Black, Auto, Mods to come soon.....

It is sometimes hard to start.It just may be that switch on the throttle.The problem started to happen after I was under the hood manually opening the throttle.That may have thrown this switch out of wack.I will test it tonight and let you all know what the results were.

Thanks
Mike Bittner

Well I removed the air filter housing this evening and started thr car. The idle was high. I rapped a few times on the Iac with the butt end of a screw driver and the idle came right down, If the problem persists I will try cleaning the valve before replacing.I've always experienced when an Iac goes bad the car will stall. Thanks to everyone for their help.

Thinking back to when I cleaned our ICV, I remember major problems with the air hoses. All the rubber had hardened, making removal of the valve impossible without replacing nearby rubber. This includes the rubber wedgie holding the valve in the manifold. My advice is to order ALL those hoses, including breathers, airflow meter plenum, and valve retainer. All can be purchased from Phil with his research, and total price was very reasonable.

Note: I did NOT replace any of the plastic couplers nor the pcv orifice, which all survived the operation fine with careful removal.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7