That lovely idle problem ive heard so much about :)

[Mr_PPP]

Hi everyone, hoping you guys can give me some advice about my babys little problems, ok i have what seems to be the well known idle bounce problem, whenever i stop at traffic lights i get the whole reving up and down business and when pulling away she dips low almost to a stall (occasionally going the extra distance ) now ive heard a lot about the 'isv' wondering if this could be the problem, but theres more also ive noticed that of the two throttle switches, the one operated by full throttle one of the cables has come away from the connector now im wondering what effect this would actually have on the car as im sure it wasnt like that when i got her (2 or so months ago) but maybe i never noticed and how would i go about replacing this, would a whole new cable be required? any help is much appreciated

[richandhazel]

I have some info on this problem on my website. Hope this helps:-

http://www.richandhazel.servebeer.com/gti/mk2/fuel/main.htm#ISV

[Mr_PPP]

much appreciated, thanks richandhazel i'll try cleaning it when i get a free day this week, still curious as to what effect the full throttle switch not being connected would have on the car though? anyone had experience of the differences between when its working and not? i was wondering whether the ecu would alter the fuel flow when flat out to perform better which would mean ive probably never experienced what the car can really do or is it not a significant difference? anyways thanks for the reply i think'll i go clean the car soon as well, im sure the amount of mud shes covered in is affecting the aerodynamics of the car through all the twisty country lanes we have around here

[richandhazel]

Can't see that the full throttle switch will have any effect on your idle - obviously the idle switch would, are you sure the idle one is ok?

[Mr_PPP]

sorry lol, my bad i didn't mean to imply that the switch in particular was affecting the idle, really was two seperate questions (shoulda paid more attention at typing better) was just curious as to how the car reacts to that switch not functioning when you put your foot down, as far as the ecu is concerned theres no change? would the car perform a lot differently when you attack the pedal with that switch functioning? thanks again about the advice on the idle problem, sorry i confused the matter a little as far as i can tell the idle switch is fine, but i will give that a check while im under the bonnet next

[richandhazel]

According to item 6 a little lower down:-

http://www.richandhazel.servebeer.com/gti/mk2/fuel/main.htm#bentley

.........a faulty full throttle switch can cause low power

[Mr_PPP]

  eek

Im on that problem as soon as poss now, to think i havent really enjoyed the joys of the real power of this car, as i used to have a 1.4 88 escort even a shopping trolley powered by the hot air of a a hair dryer seems lightning quick compared, ho hum best go get that switch sorted asap, thanks again richandhazel, mucho appreciated

[tinman]

If its 16v then this is what we found.

If its ISV, there are a number of things tht could contribute to the bad running.

(Not sure about the switches atm though).

There is an electrical unit in the cabin that also controls the idling. Not sure what its called, and its bl**dy expensive to buy from VW. Find a wrecked 16v (hang around here long enough and someone will of knocked their pride and joy into a lamp post) and nab it off that. The unit is found in the centre console. Rich may be able to guide you to it.

Find it, unplug it and see if the car behaves any differently. If the car behaves just as badly - replace it.

Next thing to start checking are the injectors. If they've done over 90k then apparently they are officially knackered. They cost ?50 odd from VW each, or ?25 a piece if you buy the Bosch part - and considering the injection system is built by Bosch, you may as well buy the cheaper part - exactly what i did.

The way the injector problem shows itself (in my cars case) is that at low revs (under 3k) it coughed and was uneven. At 3k it was perfect. Apparently at low revs with not much fuel passing the injectors are unable to make the proper fan shape cause they are worn out, whereas when they are pumping more fuel through (eg higher revs) they create the distribution spray pattern they are meant to make.

The next things to work your way down would be fuel system. Next stop is the cold idle injector or something like that, which is probably ok, then the lift pump in the fuel tank and then the main fuel pump.

Its also worth replacing the fuel pump filter anyway as its probably never been changed in its life anyway.

Tin

[Mr_PPP]

Thanks for the added info tinman, mines an 8v so i assume i dont have that extra equipment to worry about, still need to look into the idle problem this weekend, gonna start by cleaning the isv, this cars only just ticked over onto 64k so from what ive experienced all the original parts are starting to give out seeing as hardly anything has ever been changed!  hopefully theres nothing wrong with the injectors, but if the isv isnt the problem definately have to take a further look around, just like to add that tonight with a bit of diy (and my grandad holding the torch  ) i fixed the wire to the full throttle switch and what a difference! id forgotten what a handful this car can be with its acceleration, definately was like when i first bought her so put a big grin on me face, only problem is i couldnt have too much fun, my tires are nearly bare!  ho hum never ending bills but so much fun 

Thanks again to you both