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MG MGF Technical - Idle Air Control Valve Faulty?


I am having problems with the car not Idling again.

Anyone know any tests i can do to ascertain if the IACV is actually faulty?

Stu
Stu Dickens

I also need an answer. Am about to change T/B and if this does not cure the eratic idling the IACV could be the next thing to test.
Andrew Regens

IACV gets filtered air via a rubber tube from filter side of throttle body and it's easy to get to this on top of the engine. I inserted an extra piece of tubing and a cheap gate valve (off a garden hose) and used this to turn down the airflow to the iacv until the engine idles smoothly. This restricts cold start ability (you can adjust flow "up" in winter) but stops the high revving if the iacv won't close properly, and greatly enhances throttle response. I used it while I waited for a replacement IACV, took it off when the new one was fitted, then replced it the next day and left it there last 5 years!
Grant Vowles

Wip off the hose Stu - and see whether there is any gunk in the tube, or in the throttle body, stopping air flow...
Rob Bell

A surprising number of threads on this topic in the Lotus section of this site (have a look in the Elise Technical Archive using search terms "IACV" and "stalling")

IACV is often blammed for stalling problems. May need cleaning in petrol - although Scarlet Fever recommends some greygate plastic polish! Might be an idea as it will presumably help lubricate the plastic, and help prevent later build up of oily gunk?

Other problems highlighted are dodgy loom connections, and dirty throttlebodies.

I guess this is a case of going through things thoroughly until the problem is identified...

Keep us posted Stu! :o)
Rob Bell

latest news:-

Well its not the throttle body or TPS, I splashed out on a brand new one on Thursday and thought all was cured, certainly the revs drop back to normal idle ok now and don't occasionally stick at 1.5 or higher.

But after the mornings track day session when all was fine, i started it after lunch and again it wont idle again..

I drove from Anglesey to Grantham last night trying to heal toe the brake/throttle to keep it from stalling.

Again this morning it would not idle, I drove 30 miles up the road, missed a turning and turned into a side road to do a U turn and stalled it once more. restarted it and now it idles again and has been fine all day ???

I have definately got a smell of petrol though when i stop so gonna check for leaks and the breather pipe tomorrow.

This one is certainly a head scratcher

Stu
Stu Dickens

Sounds increasingly like the IACV Stu. Replacement is beckoning if a thorough clean with carb cleaner/ petrol doesn't do the trick...
Rob Bell

Stu,

I had the same problem,

For a short term fix once the engine is running un-plug the IACV, you'll find the plug on the back-side of the plenum, the engine will then run perfectly.

Tim
tim woolcott

Well today I replaced the T/B and checked all the pipes which were clean as a whistle. Still idles to high.
Andrew Regens

I picked up a replacement IACV yesterday from Victoria. It looked the same but now i have it side by side with the old one the shaft is shorter ? about half inch

I didn't realise they made a different one.

I'll put it on as see what happens anyway.

Stu

Stu Dickens


Watch the wiring to/from the valve. I went through a couple of replacement parts before discovering that i) the wiring had broken and (repeated stress at a tight bend) ii) the wiring inside the plug had broken (due to repeated removal no doubt).

Pig of a fault to fix. Quick wire-replacement-with-crimping-tool job to fix.

P.
Paul Nothard

Andrew - it does seem that the IACV is your next port of call to fix your problem.

Stu - I had no idea either. Typical. Hopefully should fit okay. Remember the TPS/IACV reset procedure (five stomps of the loud pedal with ignition at position II within 30 seconds, switch off and switch back on again), as the new IACV will be a little different to the original.

Oops, scotch that- you've got the Emerald. Plug and see; might need a little fine tuning on the laptop.
Rob Bell

Latest:-

I swapped to the replacement IACV and it seems to have done the trick although the old one was behaving itself on Sunday so I still cant be 100% its cured the problem.

Now I am trying to resolve another problem !!

The starter motor made some disgusting noises on the last day in italy which now seem to have dissappeared but. In first when pulling away i can here some clicking ?? but in no other gear?

I assume the starter motor locks in with the first gear to turn the engine over and I am wondering if its catching somehow?

I have a replacement starter motor from V just havent had the time to fit it.

hopefully that will cure the problem.

Stu
Stu Dickens

Hopefully you've sorted the IACV problem now Stu :o)

The noise is a wierd one - if the noise is only there in first gear and not any of the others, then I would probably suspect something other than the starter motor (although if that was making nasty noises in Italy... it wasn't head-butted by Zizou was it? ;o) ... I can understand why you've bought the spare just in case!)
Rob Bell

This thread was discussed between 28/06/2006 and 10/07/2006

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