UK-POLOS.NET - THE VW Polo Forum

Evening all
I've been lurking around the forum for a while now, trying to sort an idling problem by using as much info as i could that has been posted, so i don't end up repeating a question that's already been asked. Apologies if any of them do appear on this forum, but i couldn't find the answers, hopefully some of you guys can help me.
Anyway, i'll get to the point. My girlfriend has a 1997 1.4 16v with engine code AFH. We bought the car just under 3 months ago, and it's developed idling problems, which by the looks of it, seems to be quite common on here. It idles fine when cold, but once its warmed up, it develops a lumpy idle, kind of like it's only firing on 3 cylinders, with the idling speed staying constant.
At first i tried cleaning the throttle body. Didn't work, so i decided to take it to my local specialist, Autotechnik. They had it for the day, reset the throttle body to basic settings, and replaced the spark plugs and the yellow temp sensor... Still didn't work!!! Said it could be the throttle body. So i came onto this site and found it was a common fault on these cars. I ended up buying a brand new one from these guys 'www.vagcomponents.co.uk', not sure if any of you have used them?
Anyway, when it arrived, i fiitted it, and at the same time did an ECU reset by disconnecting the battery for half an hour or so. When i connected it back up, took the car for a 10 minute run, then let it idle for 10 mins.... Still there
Where do i go from here? I couldn't find any procedure you need to go through after an ECU reset, is there one? I know there is for the VR6 Corrado (My pride and joy )
As it's also a brand new throttle body, i assume it would arrive programmed with 'basic settings', or does this need to be programmed with VAGCOM? If so, is it something anyone with the software can do, or will it need to be done by a VW specialist??
Any help on this would be appreciated, or i will get it in the damn neck as it was me who told her to buy the car. 'Throttle body probably just needs cleaning' i said

Thanks
Steve

is it just under idle - no problems under power or anything?

ecu reset is usually just diconnecting the battery gor a while - although some fault codes can still exist

did the throttle body cost you an arm and a leg?!

It would suggest a spark problem / HT lead perhaps, but that would be bad under acceleration too. any water / moisture in the distributor cap? that's a cheap change.

other than that - vag-com could be useful in seeing if there are any fault codes?

Hi David, cheers for replying...

To answer your questions, yes the problem does only occur at idle, and when the engine is warm. Even just touching the accelerator will make it disappear...

We've had it on VAGCOM, and no faults are recorded... VAGCOM did spot the faulty temp sensor though, but only through it's readings. It didn't flag a code...

Funnily enough, i haven't even looked at the distributor cap and rotor arm. Suppose it's one of the first things i should've looked at, but totally dismissed it for the reasons you stated. It they were faulty, then the problem would occur throughout the rev range, right?? I'll double check it though..

The new throttle body cost £225 inc delivery and VAT. Damn expensive if it's not causing the fault, and also means i have a spare one that potentially has nothing wrong with it!!

Anyone else have any ideas??

Cheers
Steve

injectors? try running redex through there, perhaps they are a bit clogged up on tickover?

Worth a try i suppose, but pretty sure it's not that. Also, pretty certain it's not the distributor and rotor arm. When you take the airbox cover off while it's running, you can see the throttle butterfly rapidly opening and closing, so something must be telling it to do that.
Meeting up with one of my Corrado buddies tomorrow night, who's gonna have a play with VAGCOM. Will try and return it to basic settings, and see what happens.
Cheers for replying Dave, i'll let you know how we get on..

Steve

how many sensors could lead to that behaviour? anyone here know?