lumpy idle

my 1.6GTI has always had a very lump idle, ie it goes up and down from around 500rpm to 900rpm, it never just stays at 950rpm or around the mark where it should,

ive first tried to adjust the throttle cable, to hold the idle but that didnt work now ive tried adjusting the screw ontop of the throttle bodie  that also hasnt worked, so im kind of guessing there is an idle control vlave or simmilar wich is proberbly full of carbon or knackard, any tips???

also it does it when its warm and cold, so its notheing to do with anykid of anto choke,

one other thing the engine somthimes does, 1 in every 20 start ups it feels like my accelerator cable is 5cm to long ie if you floor it it takes ages for the engine to reach the kind of revs it should, this is pritty hard to describe but after 2/3 long hard revs it clears it up, any tips???

soon im going to be taking the head off to remeove some broken studs on my exhasust manifold so if any of these jobs can be done at the same time let me know, also on that topic its ok to re-use the smae head bolts isint it?

think it is!!
cheers for any help
alex

Check the auxillary belt. I'm not joking. Just changed mine and it's sorted it right out.

Peter.

i can say that i think its slightly lose, but why would that make any differnce?
need to tighen it one of these days anyway!
cheers
alex.

Yep slightly loose like mine was.

Because it aint charging the battery properly at tickover means less amps to your engine.

Just try it, it's only a ?5, 5 min job.

Let me know how it goes.

Peter.

I would check your ignition timing and also your CO mixture first. Procedures are in Haynes.

Don't re-use your head bolt, get new ones as they stretch when torqued.

Idle must be adjusted using the screw at the back of the throttle body - 7mm hex.  DO NOT adjust idle using the cable stop - If you have set it up again properly using the procedure in haynes or you will wear out your throttle body causing all manner of idle problems.

Another tip is to clean out the throttle body with carb cleaner and the air flap in the metering head.  Check the flap is centered and free to move.  DO NOT adjust anything in the metering head unless you know the procedure.

Cheers

Rich

My cab was the same & its great now, It was the a filthy air filter along with a filthy metering unit, as mentioned - Clean it - I used WD40