Thread: disco 1 likes to stall!

Usually a lazy stepper motor.
Pull it off and clean it out.
Regards Philip A

i'll give it a go & let you know.

Adnic you have inspired me.

I have had idle problems for ages (never stalled just wandered up and down the rev range sometimes). I new it was the IAC valve but never did anything about it.
Anyway I just went out and removed it. Cleaned it up (including in the hole it came from) and refitted it.
Mine was filthy.

When I first started my car it stalled 3 times in succession so I started it a 4th time and revved it up. It has been fine since although I haven't driven it anywhere yet. If it is long term fixed is yet to be tested.

The RAVE CD says the IAC valve controls the idle when the vehicle is stationary.

also clean out the throttle butterfy valve.......it carbons up and prevents air flow at idle.....
then the stepper motor tries to compensate by opening up more.....till it goes out of range........


just spray some carby cleaner on a rag and hole the throttle butterfly open and wipe of the black soot from around it......

Does anyone know how the IAC valve works?

Is it an on/off solenoid or a motor that winds the stopper in and out?

I used to hear a noise like a struggling motor when I shut the engine off sometimes. I traced it to the IAC valve. However it looks like a solenoid to me (has a spring on the shaft).

After cleaning mine last night I still have an idle problem. It seems different though. Sometimes it idles a little high, other times quite low, sometimes it is fine. However it no longer seems to change idle speed willy nilly when stationary.

I'll clean the throttle butterfly this afternoon.

It's a motor (also called a stepper motor). I belive it is wound for four positions.

My car also still gives problems from time to time. I also heard Harry's on the weekend 'hunting'.
I've now fitted a new IAC among other things, but still having issues.
Had it scanned at MR & they said it showed an AFM/TPS fault so as I had a stuttering throttle on petrol I went with a new TPS.
I would have thought that LR testbook could pinpoint each component, I'm not sure what diagnostic MR use.
I have cleaned everything religiously & tweaked the terminals on the connector plug.
Perhaps there is still an AFM problem. I am assuming the faults were cleared so when I get a chance I can get it scanned again.

There was a link here a few weeks ago to a site where there were instructions to setting the base idle speed at the AFM. There is no mention of this in RAVE, only the air bleed screw on the plenum, so I have been meaning to run that by one of the Gurus on here.

I should say my timing is advanced to 14BTDC so I know this is disrupting the base idle.

The only idle speed adjustment is on the manifold.
the AFM adjustment is MIXTURE.

There is a reference voltage applied to the ECU via a Pot. The AFM supplies a voltage proportionate to the air flow and the ECU compares the difference.

Adjusting the pot OUT leans the mixture by reducing the voltage , not only at idle but across the range. The voltage AFAIR should be 1 to1.5V. ( end terminal nearest to engine)
Regards Philip A

Aha, thanks Philip. Underconstandy now.
I took their procedure to be calibration of the AFM to tell the ECU what the baseline airflow is at idle.
I didn't want to mess with it yet tho as IIRC there was another procedure described on that site that was flat out wrong (can't remember what that was and will have to dig for the link).