Slow return to idle and hunting revs

[jtpdubz]

has anyone managed to solve this problem??
mine has exactly the same symptoms and its driving me crazy as its my daily!
could it be the springs in the throttle body a bit knackerd and not snapping the butterfly shut properly
im looking into the 51mm body to try and sort it...

[dub-disaster]

I thought mine was caused by pipes from the vacuum and fuel system getting stuck behind the arm on the throttle body . This fixed it temporarily then it cam back. Havnt driven the car and tried to sort it though the things I did and it didn't help included.
Using a completely standard throttle body - this ruled out any sealing issues as my 51mm seals better than the standard!!
Replaced all earths including run ing a separate on for lamda sensor.
Adjusted all linkages and stops for correct function of throttle - this didn't help
Watched the throttle through a mirror on the bonnet closed fine no problem !
Replaced all vacuum system with new silicone hose
Checked for vac leaks using a butane gas torch
Checked ignition time twice with different timing lights
Havnt tried chaining ecu and chip although this was going to be next on list
New coil didn't help
New leads and plugs didn't help
Checked for boost leaks no help
New lamda didn't fix it
You can try all those things although I'm convinced that hunting revs and slow return to idle is a vac leak issue I'm just thick or not experienced enough to find it !!
One more thing is Jezza once had a problem like this and was caused by the routing of his breather pipe when he removed the breather completely it stopped, I was going to try that next Aswell.
This is a realy common problem with g40 and one there seems to be no easy/definitive answear for unfortunately.

[jtpdubz]

thanks alot for reply, which breather pipe do you mean?
ill give that a go and see what happens
also its a long shot but are you running a cone filter or the airbox? might put my standard airbox back on and see if theres any difference
ive checked for boost leaks a thousand times! changed the blue temp sensor, played around with the throttle body cleaned it greased the springs etc, but none of this has helped

[Justin14100]

Hows your ISV? Might be worth giving that a serious de-gunking. One more thing there is a throttle stop on the throttle body, its on the left of the unit at the front, its a screw and a nut. try having a play with that.

[jtpdubz]

thanks for that ill have a play about today

[Jezza-7]

My pipes were all moved and it has stopped it. I get occasionally the high rev but thats cause i need to sort out the stop bolt... still.

[jtpdubz]

ok which pipes/breather pipe do you mean? and do i move or re-move to cure it?

[Jezza-7]

There is only one breather pipe on the back of the block.

[Jezza-7]

I know this is an old thread but i finally (fingers crossed) have sorted this ruff/lumpy idle hunting.

I took the top t-piece off to use some liquid metal on this small hole on the wall and with the engine running there was a very loud suction whistle sound coming from the idle hole. It sounded too loud imo so I covered it. The rpm dropped and the engine ran a lot better.

Squirted a nice amount of WD40 into it and then adjusted the idle screw till it was lower as the revs were slightly high. Were just over 1000rpm now around 900rpm.

Took it for a drive and so far its been spot on. Even round town where it usually happens, its stopped.

Not sure if it was the idle thats stopped it or the adjusting if the screw.

Anyway if anyone has similar problems, this is always a good route to take.

[metz]

T peice?

[Jezza-7]

t-piece on top of throttle body

[metz]

ah right cheers