PST2.. DME.. Drive Links.. IACV Test... questions:

[jcorallo]

Hi,

Three things:

1) I have access to a PST2 and was testing my IACV which I suspected to be faulty.

I removed the IACV from the throttle body, but left it attached to the wiring harness and left the unit on top of the oil cooler, angled so that I could see the flap.

When activating the IACV test in DME Drive Links, the IACV snaps open and closed very quickly about once a second.

I'm wondering if this is normal - I was expecting to see the flap move slowly open and slowly closed, not snap open and shut as fast as it could.

Or does this behavior mean the IACV is sticking?

2) Also can someone confirm, that the IACV flap is normally slightly open - maybe about 1/8 inch (~3mm) - at rest?

3) With the ignition on, engine stopped and the IACV connected up as normal, my IACV rattles and hums and gurgles. When I removed the IACV and shook it, it sounded loose inside. Does this mean its worn out?

Cheers,

Jules

Edited June 18, 2007 by jcorallo

[Loren]

1. That sounds normal to me.

2. The set position of the IACV is based on information the DME gets on temperature and mixture.

3. A rattling sound when you remove it is normal - when it doesn't rattle then it is usually gummed up with carbon.

In normal operation I have never heard the IACV make noise.

So what is the problem you are trying to solve?

Uneven idle? hunting?

[jcorallo]

Hi Loren,

Yes, when I come to a junction and dip the clutch, the revs sometimes shoot way up past normal idle speed, then down to a shudder before recovering back up to idle.

Also my car very nearly failed the emissions test. I have new MAF, O2, plugs - which all work - shouldnt be running bad.

With regard to my 2nd question, I meant with the IACV disconnected from the car - my flap is slightly open so was wondering if this was normal?

My IACV was buzzing which was what made me look at it. It was making a rattling / jingling / gurgling / humming sound. It made each one of these sounds over a period of a minute!!

Cheers,

Jules

[Loren]

Yeah, as I recall, when removed it is partially open. But you can usually move it around too so I don't know if the proves anything.

Again, I don't think a good working valve makes any buzzing noises. Usually I have seen the solenoid go out and the valve doesn't move or the valve is so gummed up with deposits that is doesn't move freely.

No fault codes in the DME?

Have you cleaned the throttle butterfly (front and back)?

[jcorallo]

Hi Loren,

No fault codes, I have the dumb early UK DME which is not fully OBD2 compliant, and I cleaned the throttle a while back in Feb - even then, there was nothing much to speak of to remove - all very clean.

At weekend I lubricated the IACV with some WD40 and the car has been running really well last couple of days now - so I strongly suspect a problem with this valve. The engine pulls cleanly and also I don't get the erratic bouncing-back-to-idle at junctions - just smooth now. Its a bit irritating that I havent found something definitive, but its very coincidental that after lubricating the IACV, the car runs so well now...

Cheers,

Jules