IACV (Stepper Motor)

I recently removed and cleaned the throttle body on my 97 VDP. Huge difference when driving and throttle is super responsive. I installed an aftermarket IACV which came with a red O Ring but no spacer or gasket. I did not use the O-Ring - I re-used the spacer washer and gasket (both in good shape) with HEX (Allen) keys screws and split washers.

As I am still dealing with a small idle issue I ordered an aftermarket one from one of our trusted suppliers. It came including:

b.Screws & O-Rings
c.Red O-Ring
d.Aluminum Spacer Washer

What is the red O-Ring for in addition to the spacer washer and gasket?

Interesting that the stems on the aftermarkets are shorter than the original one.

Incidentally when I cleaned the original I found it easy to move the cylindrical part and was concerned it might not be seating correctly when on the car. Perhaps someone who has cleaned and re-used the original IACV would comment.


Hmm, not sure how the shorter plunger is going to seal?
I cleaned mine when I had the XJ40 but that was a few years ago now.

I understand the PCM extends and retracts the pintle. It would appear that when the valve is new the pintle is not fully extended. That would explain why the car went to 3k rpm when I first cranked it up after putting the new valve in. I had to turn it off and on 3 times before it settled back down first to 1,200 rpm and finally to its correct resting place of 700rpm.

When I take out the first aftermarket valve I should see the pintle fully extended if I understand correctly how it behaves.


Pintle does extend when operating. I discarded the O-ring. Car is idling & running super after a week.


Good to hear you have a result.

Hmmm, replacing that o-ring is how I solved a minor vacuum leak!

If it works, I’d leave it be!

It never had an O-Ring in the first place. It had a spacer and gasket. There should be no leak with the gasket on there.There’s no O-Ring showing on the Jaguar parts diagram.

Can’t argue with you there, however, when I blew some smoke through the camcover hose (with the MAF blocked off), I was getting smoke out of the IACV. The o-ring solved that for me. Perhaps a new flat gasket would have done the same?

I suspect that’s correct.

Problem is that the smoke was coming through the top of the unit, not through the seam, where the IACV mounts to the car.

In any case, it certainly didn’t cause any problems, and I believe the o-ring fit inside the hole cutout in the gasket as well…

It is a little odd. It’s not really clear to me what the aluminum spacer does or why that recess is there as there is a gasket.