Erratic idling on Mrk3 golf since replacing the throttle valve control unit, suggestions to solve problem please??

Hi everyone,

Have posted on here a few times before. Still having problems with my Golf Mrk3 (1998 - R-Reg, 1.6cl Petrol multi-point injection, engine code AEE)

Apologies in advance for the long post, bit of a long story!!

It all started a couple of months ago, when the revs started dropping really low and causing the car to cut out when I was coming to a stop at junctions etc. Took it to a mechanic, who done a fault finder test and it came up as a faulty throttle position sensor, which is within the throttle valve control unit, but unfortunately as you apparently cant just get the sensor for my engine code, i had to get a whole new throttle valve control unit. The mechanic quoted £300ish but as he knows my dad is fairly capable with cars he actually advised that we try to get the part cheaper somewhere or the other and that my dad could fit it.
Anyhow, managed to get the part from EuroCarParts for £172, and in the carpark a very kind mechanic who was on the way into the shop to buy some parts himself, offered to fit it for me there and then for nothing as it was only a five minute job.

He changed the part over (the whole throttle valve control unit) and it solved the initial problem. Seemed ok for a few days with the new part but now has a new variety or little party tricks to keep us puzzled about, these being:

1) Sometimes when I get in the car and start the ignition, there is kind of a split pause in the process, if that makes sense? Like I turn the key and its sort of about to start then theres a pause, then it will start but......

2) when first starting the engine (with the car still in neutral and me not touching any pedals) the revs will just go vrooooooom and shoot straight upto 2500, sometimes even 3000rpm for a few seconds then calm down to normal idling range. Very embarassing when starting in a quiet street, sounds like Im a girl racer intentionally reving my car!!

3) 'normal' idling range, is now higher than it should be/used to be. Its now usual to idle at around 1200rpm and therefore makes it sound like a tank as whenever im at a standstill the car is ticking over higher than it should be and to passer by's probably sounds like i have my foot on the accelerator a bit!

4) The most annoying thing is, when the engine is warm (at usual running temp 70c) it drives ok, but the accelerator seems very 'sensitive' for example I can be driving along a road at 30ish and take my foot ever so slightly off the accelerator and it can make the car jerk. Its almost as if its running too richly if you get what I mean by that, the revs are always higher than previously and I guess this is what is having an effect on the accelaration/decelaration

5) when the engine is warm, if I am decelarating for a roundabout or creeping down my road looking for a parking space etc, the revs are constantly fluctuating between about 1400rpm and 1800rpm, but rather quickly. You can actually watch the needle on the rev counter, up down, up down... It doesnt seem to make a difference to the driving, but you can obviously hear it in the engine noise.

Does anyone know what this sounds like it could be? Whether its linked to the new valve control unit or something different? I havent got access to a fault finder without taking it to a mechanic again (yet more money).

I also wonder if there is a procedure for when you put in a new throttle valve control unit, whether you are meant to reset the ECU in any way or something?? As obviously all the mechanic in the carpark done when he fitted it for me was, unscrew the air filter element housing, lift that off and remove the old throttle body bit and put the new one in. As you can tell I dont know much about cars, but from what ive read in my haynes manual its my understanding that the ECU part in my car is almost like the brain and controls much of what goes on. Should something have been done to this when the new part went in, in terms or re-setting the revs or something???

If anyone can offer any advice would be great, preferably in easy to understand female terms please!

Thanks,
Cara

Just found something on another website, that suggests after having the throttle body out of the car, even just to clean it, that you need to reset the ECU. Which could well be the soluction to my problem?

However, the other website said about hooking car upto a computer to do this, or you used to be able to disconnect battery for half hour and this would do it also. They didnt know whether the car was too new (1998) to do this and therefore the computer method was the only option.
Anyone know if this is possible to do by disconnecting battery and if so what do i do without frazzling myself!!

thanks again
cara

Quote:

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Originally Posted by cara_essex

Hi everyone,

Have posted on here a few times before. Still having problems with my Golf Mrk3 (1998 - R-Reg, 1.6cl Petrol multi-point injection, engine code AEE)

Apologies in advance for the long post, bit of a long story!!

It all started a couple of months ago, when the revs started dropping really low and causing the car to cut out when I was coming to a stop at junctions etc. Took it to a mechanic, who done a fault finder test and it came up as a faulty throttle position sensor, which is within the throttle valve control unit, but unfortunately as you apparently cant just get the sensor for my engine code, i had to get a whole new throttle valve control unit. The mechanic quoted £300ish but as he knows my dad is fairly capable with cars he actually advised that we try to get the part cheaper somewhere or the other and that my dad could fit it.
Anyhow, managed to get the part from EuroCarParts for £172, and in the carpark a very kind mechanic who was on the way into the shop to buy some parts himself, offered to fit it for me there and then for nothing as it was only a five minute job.

He changed the part over (the whole throttle valve control unit) and it solved the initial problem. Seemed ok for a few days with the new part but now has a new variety or little party tricks to keep us puzzled about, these being:

1) Sometimes when I get in the car and start the ignition, there is kind of a split pause in the process, if that makes sense? Like I turn the key and its sort of about to start then theres a pause, then it will start but......

2) when first starting the engine (with the car still in neutral and me not touching any pedals) the revs will just go vrooooooom and shoot straight upto 2500, sometimes even 3000rpm for a few seconds then calm down to normal idling range. Very embarassing when starting in a quiet street, sounds like Im a girl racer intentionally reving my car!!

3) 'normal' idling range, is now higher than it should be/used to be. Its now usual to idle at around 1200rpm and therefore makes it sound like a tank as whenever im at a standstill the car is ticking over higher than it should be and to passer by's probably sounds like i have my foot on the accelerator a bit!

4) The most annoying thing is, when the engine is warm (at usual running temp 70c) it drives ok, but the accelerator seems very 'sensitive' for example I can be driving along a road at 30ish and take my foot ever so slightly off the accelerator and it can make the car jerk. Its almost as if its running too richly if you get what I mean by that, the revs are always higher than previously and I guess this is what is having an effect on the accelaration/decelaration

5) when the engine is warm, if I am decelarating for a roundabout or creeping down my road looking for a parking space etc, the revs are constantly fluctuating between about 1400rpm and 1800rpm, but rather quickly. You can actually watch the needle on the rev counter, up down, up down... It doesnt seem to make a difference to the driving, but you can obviously hear it in the engine noise.

Does anyone know what this sounds like it could be? Whether its linked to the new valve control unit or something different? I havent got access to a fault finder without taking it to a mechanic again (yet more money).

I also wonder if there is a procedure for when you put in a new throttle valve control unit, whether you are meant to reset the ECU in any way or something?? As obviously all the mechanic in the carpark done when he fitted it for me was, unscrew the air filter element housing, lift that off and remove the old throttle body bit and put the new one in. As you can tell I dont know much about cars, but from what ive read in my haynes manual its my understanding that the ECU part in my car is almost like the brain and controls much of what goes on. Should something have been done to this when the new part went in, in terms or re-setting the revs or something???

If anyone can offer any advice would be great, preferably in easy to understand female terms please!

Thanks,
Cara

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Hi Cara, I have had this exact same problem ongoing for around 9 months, thorough check for leaks, replaced idle positioner, lamda, temp sensor, throttle body AND new gasket, (you need to make sure they replace it with new as they perish) to name a few. VW were hopeless, automatons trained to read fault codes and replace units with no diagnostic ability at all. A few false dawns but to cut a long story short my car was a very well looked after mk 3, 1.8 gl only 70000 mls, however there comes a time when you gotta move on and cut your losses, i sold it for £150 this week!
I have just bought a 2000 mk4 1.6 16 valve with 14000 mls on the clock and just depressed myself by reading thread on here of owners of the mark 4 with EXACTLY the same kind of problems!!! Its a scandal, how long have vw been devoloping
the golf now? Build quality isnt enough. My brand loyalty is wearing thin, any crap from this one and it will be arriverderci VW.

Hi Cara,

Just came across this thread when searching for erratic revs. Anyway did you ever resolve this as your description exactly describes my problem.

My car is a Golf 1.8 cabrio on a 2000 plate. Initially I replaced the temp sensor about 4 months ago and this seems to get rid of the problem. But just recently it's back with a vengence !!

Anyone offer any pointers as to the cause. Don't really want to replace parts in the "hope" it may cure it - especially at VW prices !!

Cheers
Paul

How about getting a fault code read to help avoid guess work?

Hi Paul,

I would definately get a fault code reader done and see if that comes up with anything.
But our problem turned out to be the 'throttle position sensor' which meant replacing the whole throttle body (throttle valve control unit) was quoted £380 but managed to get it from eurocarparts for £176 although still ouch!!

However Ive also known people with this problem and simply cleaning the throttle body has solved it for them also i hear mentions of vacuum leaks or something like that causing erratic idling so there can be a whole host of things it can be unfortunately!!

And also once the new throttle body bit went in the car we had to get the ecu reset to align the throttle body or something like that, crasher can tell you as he told me!

Hope this helped a bit?!
Cara x

I come across this alot it is almost definately the throttle body needs re-aligning http://wiki.ross-tech.com/index.php/...ment_%28TBA%29 (this requires the full version of vag-com)
You could of probaly just cleaned the old 1 and re-aligned it.