16v idle and starting to run out of options!!

[H981CVV]

I've got a H plate 16v golf, it likes to hunt for idle, when the engine is dead cold its okay for a minute but once it has been going for a minute it rise's and drops between 100 r.p.m, so 950 - 1050, now i've been playing with it for a while an am slowly running out of things to try with regards to what forum members have suggested. ive carried out the following work with no success :-

clean out i.s.v really well, checked wiring then tried a different one which i also cleaned and new it worked.
cleaned all the breather pipes, removed and blew through etc then connected and checked for leaks.
removed the 3 temp senders on the side of the head and checked that they all worked with a multi meter, cleaned and refitted.
replaced both sets of injector o rings with genuine volkswagen replacements, and cleaned injectors.
replaced the control unit behind the dash with a new one.
replaced the module in the scuttle panel with a different one that i no worked.
new plugs, leads, cap, and basic bits.

and it still does it!!!! what else can i try? replacing the warm up valve? enrichment injector?

please help

[Conker]

I had an idle problem a while back. Weirdly, mine was solved by an oil flush and change as the oil was contaminated and the [excess] vapour coming from the crankcase breather was screwing the idle up. 

Anyway, during my attempts to solve it I made a fairly comprehensive list of idle possibilities:

http://www.golfgtiforum.co.uk/index.php?topic=71501.msg569972#msg569972


From your list, I would say the most likely culprit you've not mentioned is the idle switch!!

[H981CVV]

okay thanks for the speedy reply, i give it and oil change every 3000 miles and it doesn't seem to have a bearing on idle, it had a new idle switch fitted due to failure which i forgot to mention, once its warm i.e oil 100 degrees it idle okay. Could this switch be so incorrectly set up that i will still cause this? i was under the impression that its just pretty much plug and play. Also the o ring on the idle screw, i take it this is the brass hex screw on the throttle body can you completely remove it and check it then just replace it but how do you put it back where it was? screw it in all the way and count the turns?

Also that list is great, i did put a different e.c.u on it that i new worked okay. 

[rowlers]

have you had the timing, CO and idle set up correctly?
Changing all those bits will have altered any setup you had anyway.
Take it to a MOT testing place or garage and ask them to set it to 2%CO and idle 1000 +/- 50. (Crackcase breather unplugged and airbox hole blocked, RED SPADE connector at coil disconnected) timing should be 6BTDC, if std.

If it still won't settle at a steady idle, another to try is the ISV control module under dash.

[Conker]

Also the o ring on the idle screw, i take it this is the brass hex screw on the throttle body can you completely remove it and check it then just replace it but how do you put it back where it was? screw it in all the way and count the turns?

From what you said above,  it sounds like Rowlers has hit the nail on the head. Get it setup at a garage, although you can have a go yourself too:

http://www.golfgtiforum.co.uk/index.php?topic=22031.0

[monzablue16v]

If that doesn't work try swapping the three temp sensors on the end of the head under the dizzy around. It's the most random solution ever but fixed my erratic idling a treat

[Notis_kr_16v]

check the resistance at the WUR!
you might have to change the whole thing!

[H981CVV]

i've check the three temp senders on the head and they are all fine! im going to check the o ring for the tick over screw and if thats okay i will have the co2 set up properly. hopefully it will be okay. i will keep you posted.

Ben

[H981CVV]

i have just noticed that in the co2 adjustment post, it stats that if the engine isnt hunting when hot or cold the co2 is correct, mine is fine when cold and fine when hot so has this ruled out co2? also when it is idling okay the r.p.m drop nice and steady to the correct 1000 + - 50. so does this all point to the bypass screw o ring?

[monzablue16v]

i've check the three temp senders on the head and they are all fine! im going to check the o ring for the tick over screw and if thats okay i will have the co2 set up properly. hopefully it will be okay. i will keep you posted.

Ben

Have you swapped them around. Definitley one to check, mine all looked fine but one of them when connected to the dash was red hot then freezing cold then red hot etc. Got a new one from ECP and it sorted it out.