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Old 1st February 2020, 23:58   #11
trikey
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thank you, I'll try that.




Thank you, I'll get one in case just cleaning it doesn't work.
The plastic 'T' Piece deforms over time and catches on the throttle body.
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Old 20th February 2020, 23:35   #12
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Quick update: I've bought the kit with replacement gasket etc... but since then the original symptom has completely gone away! So I think I'll leave it alone unless the problem comes back, but at least now I am equipped to deal with it straight away if it does recur. If that happens, I will report back on this thread.
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Old 4th April 2020, 22:21   #13
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The problem has occasionally recurred, seemingly only after when arriving home after a run out.

As Phil-T4 suggested, when the problem was in evidence, I tried tapping the top of the IACV valve with the handle of screwdriver, and it did indeed seem to clear it. (So possibly something temperature-related sticking)

So today I set about dismantling the IACV, which was quite easy - disconnect the vacuum pipe, the electrical connector and the air inlet pipe, and then unbolt the top part of the metal casting (2 allen hex bolts).

Inside it was all quite gunky, so I cleaned it all out, as well as the pool of oily stuff that had collected in the bottom of the big rubber pipe that joins the air filter box to the throttle body. I also recovered the little plastic bit that slides into the top of the throttle body.

All easy. The most time was spent getting the remains of the old gasket off and making sure both metal surfaces were clean.

After cleaning it all, I reassembled it with a new gasket and a new plastic bit. (Haynes doesn't give a torque setting for the 2 allen hex bolts, so I just did them up to what seemed right).

A quick test running the stationary car up to temperature, and the idling speed settled to its correct 750-ish, and did the same after revving with a few accelerator blips.

I have not had a chance to do a run out yet, so I don't know whether it is fully solved yet (ref the first sentence of this post), but I hope that the 'thoroughly clean everything and replace the plastic thingy" will have done the trick. I will report back if not.

Finally, regarding trikey's comment that all this is likely due to "The plastic 'T' Piece deforms over time and catches on the throttle body", this may well be the case, but I forgot to compare the old one with the new one before I put it all back together! Actually, having had it all to pieces I am not sure what the plastic bit actually does! Once in place, it does not seem to move, nor to be able to move. Any insights?

thank you.
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Old 4th April 2020, 22:41   #14
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it does not seem to move, nor to be able to move.
Not sure.. but a fresh one does improve things!?!
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Old 19th September 2020, 16:26   #15
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ok, here's an update on the irregular idling problem, the long silence being because I had not driven the car much over the last few months, but after a 250 miles journey last week, I can now be a bit more confident that I seem to have have actually resolved it.

Reminder of symptom: Idle speed sometimes all over the place, not dropping to where it should do, and often seeming to stick and/or go up and down around 800-1200, although usually 'cleared' with a brief accelerator 'blip'.

As previously noted, I changed the IACV valve gasket, gave it all a good clean, and put it all back together. Initially I thought this had solved the problem, but after a while it came back again (indeed perhaps it had never really gone away as I was only doing infrequent short runs so could not be sure).

A couple of weeks ago, with a 250 miles round trip to Norfolk about to happen, I thought I would have another look to see if I could identify anything obvious.

Poking about around the throttle body area and the cable linkages I noticed that the mechanism was not returning fully to its 'idle', and the reason seemed to be that the white plastic bush that runs in a slot on the mechanism was getting stuck and holding the throttle position slightly open. (I think this might be something to do with the cruise control?).

Anyway, a bit of grease seemed to free it up, and it has been fine ever since (daily use and 250 miles over the last 10 days).

The picture below is taken from above, looking directly down onto the throttle cable mechanisms, and you can fairly clearly see the while plastic thingy in its slot in the metal bar, and a bit of the grease smeared in there.

Seems simple really (not sure why I had not noticed this before), and perhaps there were actually two problems (the IACV valve and the sticky throttle linkage), but hopefully my report will help others.


Last edited by david75; 19th September 2020 at 20:14..
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