g40 strange problems

[poloandyb]

hi all right where do i start...iv put a g40 engine in my polo van i only took it out the garage beggining of week for the first time out after the convertion..done about 120 miles in it all was fine..then the other night came out to it and it would start but wouldnt tickover,so started it and put some revs on and it started hunting,let off the throttle and it'd just die.
my first thought was throttle switches playing up.so picked one up today from pete off here put it on and started up ticked over great but now iv got another problem.tickover a treat but when you put your foot on the accelerator and rev it slightly and take it off again it keeps at a perminent ammount of revs like the throttles sticking but the throttle linkage is fine and moving freely.
if you turn the engine off and start it up again it ticksover lovely again untill you give it a rev and let off again,then the same thing happens (perminent revs) 

iv tried to explain as best as i could hope someone can help

[gaz g40]

the timing is spot on and we cleaned the isv out aswell plus we redid both the throttle to mani gasket and the throttle gasket itself (as the throttle can go in half)

[hayesey]

Is it a standard throttle body? Have you tried adjusting the idle screw?

[poloandyb]

no its been ported to 51mm,we messed about with the screw abit to get it ticking over and timing spot on

[Jezza-7]

This is the 3rd 51mm tb i have known of now to start doing this. Mine does it everynow and then. I think sometime the plate inside doesn't quite close properly. I have just put up with it and let itself bed in which it now has done. Sometimes it does this but only when its cold, soon as its warmed up its fine, i also get a slight hunting when im slowing down and go down the gears to stop. That gets annoying, but if i blip the throttle 2 or 3 times its sorts it out.

[poloandyb]

interesting the times its done it i turned it off pritty much straight away cus i didnt want to damage the charger

[poloandyb]

right just been out to the garage started it up revs came on fine,gave it acouple of gentle revs it did the same stuck at a certain rpm then died completely now it wount start

[Jezza-7]

Take the throttle body off and look to see if the plate gets stuck or is sticky.

[poloandyb]

i'll check it tomoz before i start work and see what its doing

[hayesey]

my 51mm plate sometimes sticks a very small amount - so the revs will hunt a little bit and you just give the pedal a tap to stop it. 

do you mean that its like the throttle is sticking all the way open?  sounds like a pretty bad throttle body job if that is the case.  ubt before making any assumptions you need to get it off and give it a good looking at.

[Jezza-7]

Mine does the same as your paul. Can get annoying.

[gaz g40]

the throttle seems nice and free but when you hold it up you can see light past the butterfly. ye we adjusted the idle screw to get it to idle as it was very lumpy to begin with and would die, we thort wed cracked it so andy revved up the car with a little blip and it stuck screaming high. im taking my car round to his to swop bits round would people look at:
throttle body
isv
and to check manifold gasket with carb cleaner to listen for a change in tone as it only revs high when the throttle is blipped

[hayesey]

seeing light around the throttle plate is normal it's not a perfect air tight seal.  I'd try swapping a standard throttle body on if your mate has one you can try.  Or try swapping over throttle cables.

[gaz g40]

aaaaa glad to see you mentioned throttle cable as it used to be a GT engine in before so its got that throttle cable still on are they different? but when you let on the throttle the cable is slack.
its doing my head in and its not my car lol

[ereeiz]

Checked for leaking / damaged vacuum pipes?