thebigman

I did post earlier but have more info on problem.
When I start the car it goes and sits at 4000rpm. I have cleaned out idle valve and throttle body etc. I have sprayed carb cleaner at the right hand side of the inlet manifold and the enging speed rises higher. The manifold is tight etc. Wondered if there was anything i could try. I was going to take the manifold off for a look but not sure whats involved.

Looked at all the pipes etc seem ok. There is a small pump like thig under the throttle body with a pipe going to the inlet manifold but dont know how to test.

Any help would be great thanks.

bythomson

petrol or diesel ?

thebigman

Sorry its a 1.8 petrol 2004 mk3 i sprayed a wee touch of carb cleaner at the right side of the manifold and it raised the speed.
Thanks

martysmartie

iTrader: (1)

Suspect a broken inlet manifold gasket (Or cracked manifold worst case scenario) or a split vacuum pipe.

Martin

thebigman

Forgot to say. Stopped in past a garage with it and they poured cold water over the inlet manifold and it dropped the revs temporarily.

tabetha

The fact the speed changes at all with spray or water means that there is a leak, ie air is getting in, most likely through a gasket, spray with easy start, and listen for the engine note, this has the added bonus of cleaning the area, and will enable the suspect bit to be identified, engines need air to run, idle is only cutting the air down, and hence the speed, it is finding it elsewhere due to a leak.
tabetha

thebigman

I took off the inlet manifold and there is a pipe connecting the manifold to another smaller plastic box i think an engine breather. The small pipe has a crack in it about 2 inch long. Do you think this would cause it.
Thanks

martysmartie

iTrader: (1)

LOL yes, the vacuum pipes are common for splitting causing air leaks, run the engine and put your finger over the crack you will most likely find the revs will drop.

Martin

thebigman

You would never have saw it if the manifold hadn't been off. Its about 6in long and about 1 inch thick with a split about 2-3 inch. Manifold gaskets look a bit burnt anyway.

Thanks for all your help.

RichieST

iTrader: (2)

That will be it then! Stick a new gasket on when you refit the manifold.

thebigman

OK Thanks again