High idle

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tmoretta
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High idle

Post by tmoretta »

Yesterday, when I started my '88 M6 from cold, the idle was around 2000 RPM. It was not until the temp. gauge showed fully warmed that the idle decreased to around 800. Is this normal cold start idle, or is something amiss?
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hornhospital
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Re: High idle

Post by hornhospital »

What was the ambient temperature when you started the engine? If it's cold enough, it can take a considerable length of time before the coolant temperature gets high enough to come off the "warm up" idle.
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plip1953
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Re: High idle

Post by plip1953 »

tmoretta wrote: Fri Feb 25, 2022 6:21 pm Yesterday, when I started my '88 M6 from cold, the idle was around 2000 RPM. It was not until the temp. gauge showed fully warmed that the idle decreased to around 800. Is this normal cold start idle, or is something amiss?
I'd say that's definitely not normal. What has it previously done at start up? Did it make any difference if you blipped the throttle? What was the ambient temp when this happened?
Phil
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tmoretta
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Re: High idle

Post by tmoretta »

Temp. in garage around 50F. Blipping made no diff. In the past idle has been high at startup but diminished more quickly.
plip1953
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Re: High idle

Post by plip1953 »

I'm sure there are others out there with all the info you might need in order to pinpoint the issue. In the meantime it would be worth doing a search for threads and posts under "idle control".

I have an '88 635 Auto and I'm honestly not sure if an M6 shares essentially the same idle control system. But if it does, I think the kind of areas you should be looking at are the idle control valve itself and the relevant water temp sensor - ie is the temp sensor reading and passing the correct temp info to the ecu which is them telling the idle control valve to close itself to the extent that rpm drops to a normal idle rate.

One particular thing that I've previously come across is that (with the engine running) disconnect the electrical plug to the idle control valve. And apparently the revs should rise. Another fairly common suggestion is to give the idle control valve a clean, I think the idea being to free off any tendency of the moving parts inside to stick. Another thing to check is whether either of the rubber pipes that the idle control valve is plumbed in to might be split and thereby allow additional, unwanted air into the engine.
Phil
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tmoretta
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Re: High idle

Post by tmoretta »

Hey thanks all. I will check/clean the idle control valve. Is it under the intake manifold on the M6? Requires removing the manifold?
tmoretta
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Re: High idle

Post by tmoretta »

Yesterday when I started my M6 the idle was at 1,500 RPM. After complete warm up it still ran at 1,000 RPM. Blipping the throttle made no difference. I cleaned the idle control valve during the winter, and for a while, it functioned well. Now it is malfunctioning again. Which/where is the temp.
tmoretta
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Re: High idle

Post by tmoretta »

Messed up on my last post. Wanted to confirm location of temp. sensor on engine.
tmoretta
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Re: High idle

Post by tmoretta »

Anyone able to tell me where I can find the coolant temp. sensor that would control idle on the S38 ('88 M6)? I know the idle control valve is under the intake (I have removed it before). I also think there may be more than one temp. sensor or sender.
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