IAC Valve - How to remove/refit. (Stepper Motor)

mgfmad wrote: Great post David

Especially after the grief I got for daring to suggest cleaning an IACV on .org :dry:

Not sure what this guys problem was -
http://forums.mg-rover.org/showthread.php?t=396265

Woow what a kicking, thats the manual boys though......all read an no idea....lol

Hmmm think I would have told him were to hide that manual too...lol

I dont know about the normal ECU but on the Emerald ECU it re-sets its self (user defined either at ignition on or ignition off)

If the standard ECU has difficulties you can always use the manual re-set anyway

The 'it says in the manual' guys need to remember that MGR didn't make money out of people repairing their own car.

They wanted to sell spare parts and have people use their dealerships.

A prime example is the Electric power assisted steering(EPAS) fault.

If your car was turning left by itself, MGR said get a new Steering column fitted.
Whereas, the fault is easily fixed by adjusting the EPAS sensor.:shrug:

Using 'Wynn's air intake and carburettor cleaner', I successfully cleaned my stepper motor today. Bear in mind that I'm not mechanically minded, the guides done by David and Clive helped me breeze through it with a successful result.

Cheers guys. :broon:

well done leigh glad you sorted that tick over problem

And a steering column is close to £1000 to replace, a club member who for some reason wont join the forum he looks in but does not see the need to register. he paid £1500 to a MGR dealer to supply and fit a new column because it was steering left. He was gutted when i told him it could have been adjusted :slapme: they will always beleive the so called experts !!!!!

bryan young wrote: And a steering column is close to £1000 to replace, a club member who for some reason wont join the forum he looks in but does not see the need to register. he paid £1500 to a MGR dealer to supply and fit a new column because it was steering left. He was gutted when i told him it could have been adjusted :slapme: they will always beleive the so called experts !!!!!

Thanks Ray and Bryan.

Bryan, I think you're confusing this job with the EPAS fault.- How to cure it . But, your point is sound though. I would never have gained the technical ability to do a job of this proficiency level without being a member here. :broon:

Both David and CJJ's pictorial guides are excellent. But to those I would add the following procedure, which I found from surfing the net whilst researching the problem I was having with the revs fluctuating.


Resetting the IACV.
Reason for resetting - The throttle has a sensor on it (TPS - throttle position sensor) that sends a 'voltage' corresponding to its position to the MEMS unit (Modular Engine Management system). This tells the computer the current position of the throttle ( ie; How much throttle you are applying) This enables the MEMS unit to calculate the correct operating parameters ( Fuel / Air mix etc).

It is important the MEMS unit knows the absolute minimum and maximum input voltage it will see on the full extent of throttle to enable it to correctly know the current position it's in. We do this by resetting it.

How to reset the IACV.
If you find that the idle speed is 'hunting' or high, try resetting the throttle position sensor (TPS). Here's how you do this:-

Warm up the engine to its normal operating temperature (the engine requires extra air and fuel when cold). This is actually what the IACV - idle air control valve manages.

Switch the ignition to position 2 so that all the dash lights come on but don't start the engine up.
Press the accelerator down slowly to the floor 5 times in 30 seconds.
Wait for 15 seconds.
Turn off the ignition.
The TPS has been re-set and the engine can now be re-started.


You could give this a try before you clean or replace the IACV /Stepper motor. But you should also do it after you have done either of those two jobs as it apparrently allows the ecu (engine control unit) to re-learn.

As David wrote, every engine start throttle body is closed and the required amount of air the engine gets over IACV.
My experiences are the same as far as cleaning IACV. The first time was successful (cleaned with WD-40). After 3000 miles I tried again with a clean, but no real results so that I change IACV. Unstable rpm tachometer on the idle RPM 900-1100 :yesnod:
Motor-multi point injection stepping - 4 Pin connection - Genuine MG RoverPart No.: MDQ100170 (SBZ005 2403)

Motor-multi point injection stepping - 4 Pin connection - Genuine MG RoverPart No.: MDQ100170 is correct for the TF. It is worth mentioning that you should ensure that you buy the correct IACV as the old ones (Fs) don’t fit the TF and the TF has a 4 wire connection (the one in the picture above) and a five wire one. They are not interchangeable. :nonod:

Another thank you to David and Clive! I stripped and cleaned my IACV today with help from their instructions.
Those two bolts certainly are hard to get at. I was glad that my collection of too many tools contains a very small
driver bit ratchet.
While taking things apart I also discovered a badly split breather hose which I am sure contributed to my idle problems along with the very dirty stepper motor.
This will give me an excuse to order a set of nice shiny new silicone breather hoses from PTP. :woohoo:

David Aiketgate wrote: The earlier IACV looks like this. It is removed/replaced in the same way.

If one is just cleaning the early style valve it is easier to split the two halves in-situ by removing the two screws than trying to access the lower screws that hold it to the inlet..

This is a great guide. Just replaced mine with a spare as I had an unstable idle issue .

A pity that the garage I took it to couldn't seem to solve it???

I agree, this thread has been a great help.

However I have a question if anyone can answer please.

I fitted a salvaged stepper (to replace one I ruined by trying to clean it !) and idle seemed to work fine until I took it for a long run with the heater on full blast.
The 'hunting' came back . When I turned the fan down to 2 it disappeared ??

Now I guess this has something to do with air flow available whilst stationary.

Because this has happened with 2 steppers (the one I cleaned wasn't very dirty in the first place and the salvaged one came with a guarantee) does this suggest a different problem or should I bite the bullet and pay £45 for a new stepper ?

Thanks in advance