Right a little bit of background 1st:- Polo 6N 1999 1.4 16v AFH with 76k miles. Full service in July with brand new throttle body fitted. Recently the rear box has started to go and although not noisey i left it a few weeks before i replaced it and last week put just a std cat back system on. However last week the polo started doing the classic dodgy throttle body symptoms with a high idle of 1100-1300 , holding revs between gears and when in traffic the idle will 'bouce & surge' erratically up 2k before dropping back once the car came to a standstill. Oh and in general my daily drive is a mix but i'm only averaging approx 27-28mpg

So yesterday i dropped the car in with the garage who fitted the new throttle body in July & FOC they checked everything over and reset the throttle pot via VAGCOM - picked it up lunchtime and the throttle body is clean, there's no fault codes, all the sensors etc appear ok and the idle was back at 900. Chatting it over they suggested the problem could possibly be CAT related - i was hoping it was a duff temp sender or such....

Now by the time i got home last night ALL the symptoms were back

I really would appreciate any help/suggestions on a fix as this is really starting to pi$$ me off now.....

Dan

Tell me bout it...I have the same problem...

Everytime i dip the clutch the revvs will surge and stick there till i come to a stop...Really annoying...And destroys the MPG

Plus it never idles very high at 1200 rpm...

Vagcom returns no faults...

So what I'm gona do is...check for a vacuum leak at throttle body...then replace the air filter...then temp sender...then throttle valve control module

see how it goes...

Edited 6 December, 200718 yr by gavin89

I've got this with a customer's car as well. It came in almost as a non-runner with the cams mistimed, a carb Mk2 dizzy with the vacuum advance removed and a variety of other problems. I gave it a full service, did the cambelt (properly this time), changed the dizzy for the correct one, ran a 1551 diagnostic on it and changed the battery (which was knackered, although that was unrelated).

Gave it back to the customer and it was a-OK, then an hour or so later he rang me to tell me that it was doing the tacho dance. I found 4 seperate vac. leaks which I cured, and we changed the temp sender and cleaned the throttle body, all FOC.

Guess what? It's still doing it I was not amused. It's the only 6n 16 valve that we look after and it's being a right pain :(

mines doin this too, changed the temp sender, new throttle body before i got the car, disconnected the battery for an hour.

its a 1999 too but with 62k.

mines doin this too, changed the temp sender, new throttle body before i got the car, disconnected the battery for an hour.

its a 1999 too but with 62k.

and its still doin this?

i replaced a new airfilter today...still same problem...idle is too high

yeh, its not all the time tho. very rarely after i drive a few miles. it only revs itself under 1400rpm tho, never higher

forgot to mention, that when it idles high, if i put a little pressure on the engine by turning the steering wheel while stationary, it will bring the revs back to normal.

Same here desta or if i hold the brake and pull the clutch up to drag the revs back down.

I had a more detailed study with my VAGCOM.

Noticed some bizzar things...

The temperature dial is bang on in the middle of the clocks. So it should be 90 degrees C. VAGCOM reads coolant temperature as 60 degrees C!!

Temp sender problem...almost certain!

Throttle position sensor after basic settings is performed: when cold is 9.9 degrees...when warm settles down to 7.8 degrees...(factory default say should be 4 - 6 degrees)...

Another thing is the graph log of lambda sensor...the responce (sine waves) should increase inphase proportional to the engine revs/min. Therefore responce goes up when engine revs goes up. In my case the freqency gets lower with no increase in amplitude...bit odd.

According to this thread it is an ECU problem and the only solution is to just get a newer ECU according to VW. Only thing is I also get these problems but my car is only 1.4 8v.

Possibly we could compare ECU numbers?? Maybe rule out or conclude this as the solution.

Simon

According to this thread it is an ECU problem and the only solution is to just get a newer ECU according to VW. Only thing is I also get these problems but my car is only 1.4 8v.

Possibly we could compare ECU numbers?? Maybe rule out or conclude this as the solution.

Simon

I thought it was only AFH ECUs thats been affected...

Same here desta or if i hold the brake and pull the clutch up to drag the revs back down.

i meant...when i turn the steering wheel, then release it, the revs will go back to normal and stay back to normal.

Add me to the list , changed the throttle body , dizzy cap , spark plugs ,temp sender ,thermostat and i have cleaned the throttle body . The car idles at 1000rpm and sometimes , well all the time goes up to 1200rpm it is starting to piss me off . I need to fix this problem!!!!

wish my new valver was as reliable as my old 8v. hmm, I'm sure there must be a fix?

how much is a new ecu going to cost?

This is the thread I was talking about, it doesn't list what engine codes are affected only what ECU model numbers are. http://www.clubpolo.co.uk/forum/index.php?showtopic=52691

My engine code is AEX but not sure about ECU number but will find out.

Simon

i have a 6n 8v. and it idels at 2100 ..lol

fucking piss take

still having this problem.

when i changed my temp sender, i replaced the old yellow one with a new blue one (both 4pin). the blue one had a big silver bit on the end and the yellow one didnt.

is the blue one a better version of the yellow one? because when i went to VW to ask for a new temp sender for my car's reg plate they gave me the blue one.

should i try fitting a new yellow one?

I've got the same one mate they just said it does the same job as the yellow one , and they dont make the yellow one anymore .

try optimax or high octain fuel.. not sure why but it fixed my problem

still having this problem.

when i changed my temp sender, i replaced the old yellow one with a new blue one (both 4pin). the blue one had a big silver bit on the end and the yellow one didnt.

is the blue one a better version of the yellow one? because when i went to VW to ask for a new temp sender for my car's reg plate they gave me the blue one.

should i try fitting a new yellow one?

How much did you pay for the temp sender mate?

about £27 with vat

aparently the poloace chip will cure the problem associated with the ecu. go to the fahreghein tuning bit under "16v offer".

Edited 18 December, 200718 yr by desta

Nice to ressurect an old thread :)

Was there ever any conclusion on this? My 1996 6n 1.4 8v is doing this exact thing. Sits at 2000rpm for at least 30 seconds and then drops down to about 900rpm every time I come to a stop. Any help would be appreciated, or even advice on a good localish mechanic in South leicestershire or Rugby area.

I'm currently having a very similar problem with erratic revs as discussed here:

http://www.clubpolo.co.uk/forum/index.php?showtopic=123729

Have had it looked at today and confirmed that the throttle position sensor is buggered and a new throttle body will be required. Apparently it's a fairly common fault on the 6n.

Mine is sort of the same... It idles fine but as soon as I do anything electrical like opening the windows my revs drop, and even just turning my steering wheel does the same!