Idle stepper motor (Spi version of the ICV)

[Envoy CDX]

Does anyone know how the Idle Stepper Motor works?

[Robsey]

I found this on another forum, it sort of explains what the ICV or idle stepper motor does.

The purpose of the idle control valve is to provide air to the intake of the engine when the throttle plenum (butterfly) is shut so ONLY when the engine is idling. To cut down on emissions the ECU checks the lambda sensor in the exhaust for the mixture and measures out the minimum possible amount of fuel to inject and the minimum possible amount of air to allow to bypass the intake plenum through this valve to get the perfect mixture on idle, giving you a nice smooth idle and no rich smells.

The problem with this is that the idle control valve can occasionally get little bits of oil blown back through it from the engine breathers causing it to stick slightly. When this happens it can give you poor idling, cutting out, jerkiness on coasting, jerkiness on acceleration, poor acceleration etc.

[Envoy CDX]

Yup, that sounds like the ticket for me.

[Robsey]

I believe it is possible to clean out the ICV, possibly with carb cleaner (I presume).

Although, it shouldn't take long to wip out yours and fit the replacement in it's place.

Quicker to replace than clean, I would have thought.

[Envoy CDX]

replacement is pretty oily too, but gives me a chance to see whats its like withthe new one. T20 screws hold it in place under the injector.

[Robsey]

sounds like the good old "clogged breather system" scenario to me.

[Envoy CDX]

The joys, Going to have to do some stripping down on the engine.

[Robsey]

Will this be another world famous How 2 ?

[Envoy CDX]

Probably, depends how awake I am when I do it

[Robsey]

or if you can fit it into your very busy schedule!!

[Envoy CDX]

Replaced the ISM today, initial turn of the key and I thought "bugger, it's not worked.. as it ran barely at 350-400rpm and was hunting badly with the EML light on, gave it a little blip and it soon sorted itself out and idles at around 600-650rpm now.

[Robsey]

I think that is still a little low, but I could be wrong.

I thought it was more towards 750 to 850 on an auto.

Anyway, as long as it runs smoother, then the jobs a good un !!

Good news.

[Envoy CDX]

It is low should be 800-880 but its smoother and not as erratic so alls good.

[Robsey]

Will probably get closer to the correct idle rpm after the ECU learns the new valve's parameters.

[Envoy CDX]

Yeah, it started hunting between 600 and 1000 rpm today, but it didn't sound like it did, so it's probably learning.

[Robsey]

Will probably get closer to the correct idle rpm after the ECU learns the new valve's parameters.

forgot to say, assuming you disconnected the battery to reset the ECU to allow it to re-learn everything.

[Envoy CDX]

Toyed with doing that overnight.

[Robsey]

forgot to say, assuming you disconnected the battery to reset the ECU to allow it to re-learn everything.

I read somewhere, that whenever you change anything, especially sensors, or sensor controlled items, then you should disconnect the battery for about thirty minutes or so.
Then reconnect up, and take your cav for a brisk blast down the motorway.

Don't know how much truth is in the notion that the car should then run more economical and smoother, when you drive at a less riotous rate!!

[Envoy CDX]

Might have a run out for a coffee and disconnect the battery then reconnect it when I've finished

[Robsey]

Great ! - Mines a Latte

[Envoy CDX]

Great ! - Mines a Latte

Let me know when you hit Weatherby then.

[Robsey]

Has this settled now then?

If not fully sorted,
Suppose you could just clean it with carb spray, and then re-lube with 3 in 1 oil, just to be on the safe side.
You could do this on your original one, swap them back around, and see what, if any difference there is.

If it is sorted, then you could always clean the old one and keep it as a spare.

[Envoy CDX]

Has this settled now then?

If not fully sorted,
Suppose you could just clean it with carb spray, and then re-lube with 3 in 1 oil, just to be on the safe side.
You could do this on your original one, swap them back around, and see what, if any difference there is.

If it is sorted, then you could always clean the old one and keep it as a spare.

Half my trouble is I never throw anything away I have rattley backboxes kicking about just incase
I will probably clean the old one at some point. Need to knock the battery off at some point and let it "reset" itself.

[Robsey]

There you go, convert to a V6 or V8 short block, and use two back boxes.
One for each bank of cylinders.

Hmmm but then you find you have barely any space for the working spares.

[Envoy CDX]

There you go, convert to a V6 or V8 short block, and use two back boxes.
One for each bank of cylinders.

Hmmm but then you find you have barely any space for the working spares.

Aye, need to have a really big tidy out at some point.