UK-POLOS.NET - THE VW Polo Forum

Hi everyone, am new to this forum having just bought a Mk 4.
The vehicle is a 1.0 L AER engine 6N1. 1998. showing 80k on the clock.It has sevice histiory to 60k but after that the servicing gets a bit vague.
Being my daughters' first car I have given it a check-over and done/found the following things.
Changed air filter, oil, oil filter, fuel filter, pollen filter.
Renewed plugs, (old ones rusty !.)
Renewed rotor arm (rusted to distributor shaft !).
Renewed distibutor cap and leads (old cap showing signs of tracking !).
Renewed auxillary belt and renewed cam belt, plus new tensioner.

After doing the above, I took the car for a run yesterday.The car starts first time and ticks over, "sweet as a nut", and accelerates krisply.

PROBLEM.
After the car had warmed up, when you come to stop the cars' idle goes below what it should be and tries to stall.If it doesn't stall the revs pick up and it ticks over ok.It seems to be occurring on "over-run".Once the car regains idle it ticks over sweetly and will rev up and down and return to normal idle speed without any signs of stalling.It only seems to happen when you are actually in motion coming to a stop.
I have checked to see if any pipes have been dislodged and found none.I haven't disturbed any of the fuel system apart from the new fuel fliter, which I have checked, and is on the right way,and not leaking.
I have added the stated amount of Redex injector cleaner to the fuel in the tank........could it be that?.
I am hoping that someone could point me in the right direction as to the cause of this problem and how I might rectify it without wasting time changing and testing sensor etc.
Your response will be most welcome...many thanks Ron H.

hi i would try a throttle body clean and carry out base settings on it

Thanks to Yorks for such a quick reply.
Must admit had more time yesterday evening to look at some threads on the forum and saw that idle problems on Polos are quite common.Having read a few , I see the consensus seems to be to clean the throttle body with carb cleaner, and then disconnect the battery for half an hour to let the ECU reconfigure itself,.....although one person said this was "an old wives tale and didn't work !.
Some also said that, after cleaning, their tick-over raced for the following few days and then settled down to normal....is this correct ?.

I like to do things correctly, and see that OBD leads are readily available on E-Bay and that VAG Com is free as a download from Ross-Tech.Can someone tell me of their experiences with these items and if they are as easy to use as implied.Rather than use "tricks" to set a car up, it must benificial to do the work as it would be " hopefully done" at VW.
I presume,with VAG Com any faults can be detected and, hopefully, if i clean the throttle body, the ECU can be reset afterwards.
Any input would be much appreciated.......RH.

as said, clean the throttle body out and carry out the basic settings, best done with vas 5051, can b done with vagcom 2 i think

Someone might find this interesting.
After cleaning the throttle body, the problem went from almost stalling when pulling up, to racing between 1200-1500 rpm. when taking your foot off the throttle....only stablizing at 700rpm when stationary for about 5 secs.Having disconnected the battery terminal, on refitting the throttle body, i drove the car expecting the idle to settle down after a few days......it didn,t!.
As this is my daughters first car, in this condition, there is no way i would let her drive the car.
I took the car to an independant who wanted £50 to reset the ecu...more later!.
Not one to throw ones money away, on looking on the internet, I saw that Ross-Tech mention that a TBA may be needed if...
A.The vehicles battery is disconnected and re-connected.
B. The ECU has been removed and reinstalled.
C.The throttle body has been cleaned or removed and reinstalled.
D.The accelerator pedal has been removed or reinstalled.

If this is the case, then a TBA might be needed every time the battery is disconnected.........at £50 a pop that could get expensive !.

I have now invested in the program and the lead needed to perform the procedure myself.Bearing in mind i hadn't done it before, the procedure took all of 10mins...........if i did it again...... 2min max ...not bad if you are charging £50 !.
The process worked, and the cars idle is correct and revs sweetly!.

Whilst looking into VAG-COM, it was pointed out to me that on some Polos with MP9 ECU.s they might not take Basic TBA adaption from VAG-COM
without running a program to ERASE THE LONG TERM MEMORY from the ECU.This is a differant program, downloaded off the internet.It was pointed out to me that i might have needed to perform that process....i didn't!.
This proceedure is known to VW evidently, and they use it to cure MP9 ECU associated problems.

From my experience, disconnecting the battery after cleaning the throttle body, will only work if you are lucky....I apparently wasn't !.