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mk4 golf 1.6se auto 1999 eratic idle

As per subject really.

Since its service at a VW specilist who are claiming its nothing they have done and would cost me a "exploratory" charge to diagnose the fault. Basically when ever I put it in to park the revs bounce all over the place, never over 2000 rpm. Although it could be a fault that co-incided with the service.

I tried a throttle body with VAG-COM, which would not let me do it. I have the full verson aswell.

So far I have tried cleaning the throttle body with carb cleaner sprayed on a clean rag around it, top and bottom, it was removed. I put it back on and tried to align it again with no joy.

Also I sprayed some electrical cleaner on the electrical contacts in the air flow meter which a local ex vw tech said to try. He also said to remove the throttle body and remove the black cover on that which houses the throttle position sensor I think he called it and pray some electrical cleaner on it and let it dry out in a clean place as even a small bit of dust can play havoc. Neither have worked.

He reckon a bouncing idle in park indicates a vac leak which I cannot find for the life of me, he said usually its the plastic pipe from the air flow meter to throttle body which is gets small splits. So I replaced that. It didn't work.

He thinks its now time to start replacing the offending parts starting with the air flow meter, and if that fails then the throttle body. He suggested the air flow pipe first as its the cheapest.

Its one or the other he says so its 50/50. I think the AFM is about £60 from GSF, he recommended a genuine one from VW though.

Has anyone any other ideas on what might be causing this or should I just replace the AFM first hope it goes away then the throttle body ?

It could be time to let a garage take care of it but that will cost more and then parts etc. I reckon they will only diagnose it as one or the other ? or possibily find a vac leak some where else ? (although my friend couldn't find a leak, he was spraying wd-4o around pipes listening for engine tone changes I think he said he was doing and nothing)

Pfffft what do you guys reckon ?

Reply to
Pete
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have you checked for vacuum leaks?

Reply to
Mrcheerful

I have checked the pipe between the air box and throttle body and replaced it with no joy under the advice of a friend who is a mechanic. I'm just a hobbyist where else can I look ?

Reply to
Pete

You could look at the thread on this at:

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The

salient points seems to be;

OK this is the answer and why it happens.

When you clean the T body - spray and or rag as well, you are removing the deposit from the body.

After doing this, the position of the flap is altered ever so slightly.

Why - as the material builds up, the shaft which the flap is attached, this is connected to a computer at the end - plastic bit on the TB. Why its not noticeable as the car gets older, the computer learns and makes corrections ever so slowly.

Once you do a clean the TB the alteration is too large for the computer to compensate hence the erratic idle.

How to fix - you need to do a basic setup by attaching the computer to make those idle adjustments.

This you can't do yourself BTW.

Another hint is that some cleaners will enter the TB computer and dissolve the circuit board so be careful.

Reply to
krak

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Interesting read. The problem occured before cleaning the TB and I did try a TBA (throttle body alignment) with no joy. Although I wonder if the TB was cleaned on the service and the circuit board was damaged. I hope not as this part is over £300 from VW although no doubt cheaper from euro car parts.

Reply to
Pete

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Seems that when it was serviced, a junior mechanic without any VW training may have shot some cleaner down the tube to make it look clean, unaware that it affects the circuit board.

I can ask later if its as critical on this particular model but seems to be in the scheme of things.

You could always pull thr cover on th TB and visually inspect it.

Reply to
Rob

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Balls, so it looks like it could be the throttle body that has been mullered from lack of knowledge by the garage or just someone not thinking right. They are arsey to deal with at best. I think I should call them and see what they say. I put a lot of money through them with this and another car. If they want to lose me as a customer its not an issue for me. I hope they do the decent thing.

The model Rob is a mk4 golf 1.6se 1999 aeh engine. Also to add its an auto.

I have inspected the TB and its shiney as most new, with slight rubbed of areas on the side walls very light kind of like a sace pan after some time of using it.

Hmmm I wonder if a cheapy off ebay could do the trick or if I should head to vw - gsf- euro for one :( .. I feel my wallet about to lighten.

It has affected my fuel consumption unless there is another part failed since this has been done.

Do you think it could still be the air flow meter I only ask as its a cheap part ?

Thanks kindly all for the info so far proved very helpful! ... although I get the feeling I need a new TB and AFM pffft the cheap skat in me says used break yard parts considering its a 1999 car but these kind of parts can be quite fragile.

Reply to
Pete

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