YOUR M44 Idle Control Valve

[Eric]

Just wanted to contribute my 0.02 about the M44 ICV.

My car was laid up for a while, and while the intake tract was sitting in the barn, the ICV froze up, which resulted in a near-inability to idle when first started (tried to idle around 450 RPM), with no ability to deal with dropping back to idle after revving, or even after turning on the headlights or the A/C. The observant would have noticed that the usual under-hood quiet buzzing was missing. Also, the OBDII threw a P1550 code, which was sort of a giveaway. Interestingly, because of the adaptive nature of the OBDII system, after five or ten minutes, it "learned" that the ICV was stuck, and how far open, and compensated by setting a steady idle of 1500 RPM.

I looked up what I could find out about the ICV, which was essentially nothing, other than the fact that it can be cleaned, so I went out and took it off and checked it out.

The ICV is the way that the computer controls the engine idle, and keeps it steady regardless of temperature, accessory load, etc. It allows varying amounts of air to bypass the closed throttle valves, depending on the signals it receives, so the computer can control the air entering the system, which, along with its control over the amount of fuel injected, allows it to control the idle quite tightly.

All the ICV is, is a tube, with each end connected to a passage in the intake manifold, with a sort of a rotating "flapper valve" that can interrupt the flow of air through the tube, controlled by an electrical solenoid, which cycles it open-closed at an appropriate duty cycle to admit the desired amount of air.

Nothing to it, really, bit if you want a new one, it'll cost you $150 to $200.

Removing it is easy - it's held on by two T-30 Torx screws, and has a flat gasket between it and the manifold.

Once it's off, you can look into it and see the valve that bounces back and forth. It should be movable, with a bit of resistance and bounciness because it sits in a strong magnetic field, which will make it want to sit in one or another position.

If it doesn't move freely, or if it is obviously blocked up, it can be cleaned.
Others have suggested carb. cleaner, but be advised that this thing has one internal O-ring, which could be damaged by carb cleaner, and may swell and make it impossible to reassemble the unit if you disassemble it further.
There's no rocket science here - try to avoid scratching the thing up too much or bending it, but you don't need to remove every last scrap of crud that you find in there - it's just letting air in so the motor can idle, it's not a high-flow, high-performance part.

If it's really stuck like mine was, you may need to take it apart.
The unit consists of two halves, held together with little cams, like the bolt of a rifle. The cams are parallel, not angled, so it doesn't tighten, and it has no "on" or "off" direction - it will come apart and go back together either clockwise or counterclockwise. It is prevented from rotating open by a thin brass roll pin, which you may be able to pull or pick out, but which is probably easiest to drill out. The hole can probably be threaded to accept a small screw, or you could just force or glue any solid bit in there - it's just to keep it from rotating, which it would be very unlikely to do anyway (I left mine without anything in it because it was tight enough to feel secure).

Once the roll pin is out, just rotate the halves in either direction about a quarter to a third of a turn and it should pop open. It will be a bit hard to pull the two halves apart because of the powerful permanent magnet in the valve half - you're not going to break anything, just pull them apart.

Inside, you will find an O-ring sealing the two halves and a spring washer that puts pressure between them so it's hard for them to rotate apart or rattle.

You can now grab the magnetic end of the valve half, which used to be inside the other half, and rotate it back and forth to loosen the valve. Some carb cleaner or penetrating oil may help loosen things up. Play with it until it's floppy and loose.

The whole thing just slips back together. If you got carb cleaner on the O-ring, it will be swelled up, and you may not be able to fit all of the parts together. Any hardware store should have a replacement. Just push it back together, line up the cams, twist, and align the roll pin holes, and you're all set. As mentioned above, use your own ingenuity to stick something in that hole to keep it from opening up later on.

Reattach with the two screws. Use a small amount of any innocuous sealant on the gasket. Tighten to about 5 foot pounds (like you would for screws, not like you would for bolts).

That's all there is to it, an easy way to save $200 and God knows what a shop would charge for the labor.

Enjoy the photos.

- Eric