uneven idle and hissing

[Jovic82]

alright

i seem to be having a few issues controlling the idle on the car, it is regularly hunting when i first switch it on and although i have had a quick look under the hood for any loose hoses i cant see any.

to make sure i revved the car from idle and listened under the bonnet and as soon as it revs i can hear a short sharp hissing sound from under the plenum area. I take it this would indicate a loose hose underneath but just wanted to make sure it isnt normal before i take it all off!

cheers

[g20wel]

it could be the the inlet gasket mine did the same

[Jovic82]

which gasket is that? is that the one that goes between the upper and lower manifold?


cheers

[Prof]

What gen is it ?
 
There are quite a few vac hoses around on the stock engines - anyone of them could give symptoms you describe - classic vac leak.
 
But as g20wel said - could also be one of the inlet gaskets - there\'s one between the block and the lower inlet manifold and one between the lower and upper manifolds.

[Jovic82]

it is a third gen prof,

yeah i have already had a few hoses come off that were visible but i have reattached with cable ties and they have stayed on . the two gaskets sound likequite major jobs though! fingers crossed.

[g20wel]

mine was a rip in the uim to lim can fix it in 15 mins tbh

[Jovic82]

well i would make that half an hour if i was doin it! how much is a new gasket for that?
cheers

[Prof]

mine was a rip in the uim to lim can fix it in 15 mins tbh

Yep - that one can probably be done without taking much in the way of pipes off.
 
You might want to try the flammable spray trick to see if you can pinpoint the source of the leak.
 
When it\'s idling - spray something flammable (propane/butane gas or carb cleaner) in different places to see if the engine note picks up - the idea is that the added \'fuel\' will offset the air being pulled in and the engine revs pick up slightly.  I\'ve found a couple of hose clamp leaks this way.  As long as you\'ve no stray sparks or exhaust escaping - and use something very volatile that will evaporate quickly it will be ok - but be careful !!

[g20wel]

as prof says that is a good test
i tried to get one from rotaryart but they never posted it
so i used a very high temperature high quality gasket compound its been on for months now and works a treat

[L18M]

i was taught to use wd40 by benlewismay i think it was

[Prof]

i was taught to use wd40 by benlewismay i think it was

The solvent in WD40 works ok, but WD40 does carry a silicon compound - not sure what that\'s like in the combustion chamber.
 
Carb cleaner and similar compounds are basic hydrocarbons with other compunds that contain oxygen as well - so it\'s all combustable - no residues to worry about.

[Jovic82]

cool, thanks guys im going to have a stab at removing the uim over the weekend so will give the carb cleaner a test run first to see how it comes out.

thanks