Idle Control Valve Issue

[JHZR2]

Hi,

My 91 318i has had hot start issues for a while.

Ive tracked it down recently to the ICV. When the car is hot and I unplug the ICV harness, it starts perfectly.

Well, started the car up cold today with the ICV unplugged, and it was terrible. Not only was the idle rough, but the emissions from the car was really bad, it stunk real strong.

So Ive not only confirmed that the ICV is the culprit, but also that the ICV works, at least under some conditions.

Now what?

Do I clean the ICV? If so, with what? If I clean it with solvent, how should I re-lube it?

Thanks

 

[oggb]

I'd clean it with something that's plastic-safe. CRC MAF cleaner comes to mind.

When you turn the key to "run" do you hear the ICV stepper motor make noise? Does that engine have EGR, and if so - have you ever cleaned it?

Edit: I'm not sure why I'm recommending plastic-safe solvent. It makes me feel better. Also, you don't need to re-lube those. Keep 'em clean and they should last a good long while.

 

[The_Jeff]

Not sure it needs lubing. Check the passageways for blowby type goo, preferably by removing the valve.

This is total hackery, but consider raising your base idle a touch with the "don't touch this screw" screw. This will have the ICV operate in a different part of its zone.

If your idle is too low, you don't get 22 inches or so of vacuum, so your fuel system thinks you're making power, so it dumps fuel before it finds closed loop. Hence your smell.

 

[JetStar]

Well I don't work on cars for a living, but it would seem that it is moving? Can you see it move if you remove it but leave the harness connected. Can these get a bad spot in them? The one's I'm familiar with have a stepper motor with position feedback and a jackscrew connected to a pintle. I've seen testers for them as well. I'd also be concerned that the computer is commanding the wrong position due to another fault. my 0.02.
BMW 4m's?

 

[JHZR2]

Originally Posted By: eljefino

This is total hackery, but consider raising your base idle a touch with the "don't touch this screw" screw. This will have the ICV operate in a different part of its zone.


This would be interesting to play with on multiple vehicles. This exists on computer controlled, fuel injected engines? All of mine are. The only carbs I have are in my pasta bowl and on my lawnmower.

 

[oggb]

Originally Posted By: JHZR2
Originally Posted By: eljefino

This is total hackery, but consider raising your base idle a touch with the "don't touch this screw" screw. This will have the ICV operate in a different part of its zone.


This would be interesting to play with on multiple vehicles. This exists on computer controlled, fuel injected engines? All of mine are. The only carbs I have are in my pasta bowl and on my lawnmower.


My ICV on my Mirage works, well... it works when it wants, how it wants. So I did like eljefino suggested and followed the service procedure for adjusting the idle and set my idle at ~850 ish RPM instead of the factory 750 RPM.

It's a night and day difference. Idles much better now.

 

[tomcat27]

I use carb cleaner; and only clean the cone-shaped pintle and passageways.

 

[bepperb]

Common problem on Toyota's. Never heard of anyone lube it. Once read, on here I'd guess, that there is some oil residue left behind when one uses throttle body cleaner.

Either way, it does sound like you have the culprit.

 

[The_Jeff]

Originally Posted By: JHZR2
Originally Posted By: eljefino

This is total hackery, but consider raising your base idle a touch with the "don't touch this screw" screw. This will have the ICV operate in a different part of its zone.


This would be interesting to play with on multiple vehicles. This exists on computer controlled, fuel injected engines? All of mine are. The only carbs I have are in my pasta bowl and on my lawnmower.


Yeah because you can't have the throttle valve close all the way, it will jam and or wear the metal. The typical set up is to have it be 100 RPM below hot idle with no accessories on. IDK about throttle by wire cars. If you raise it too much you might throw a code. If you have to calibrate the TPS (elongated mounting screw slots that let you twist it) you might have to recalibrate it. Come to think of it, you might need this anyway-- a TPS indicating 1% throttle to the computer says, don't bother controlling the idle, the driver is driving.

EPA makes them idiot proof the screw some how, with a security bit, a cover, something.

 

[mechtech2]

You can set the base idle a bit higher, but the IAC motor and computer will compensate.
There is a very narrow range where it can be set and be OK.

A good safe cleaning of the IAC motor what I would do at this point.
And don't forget to clean the throttle body real nice. They go hand in hand.