Lude Generation

my mate has a similar issue to doubledanny on his h22 4th, only when hot though, engine revs to about 1500 then drops to 800 then raises again. engine idle is hunting. spoke to nathan on the blower yesterday and he suggested the iacv, so we had it off and cleaned it and thought it was cured but when it got hot again it started to hunt again.

so the next thing i did was look on forums and found that their are 2 holes inside the throttle body just before the throttle plate on the left as you look inside. plug the bottom hole with finger and if idle changes then the FITV needs replacing. but no change engine stayed high.
so i blocked top hole and idle returned to normal, what is linked to the top hole?

here is a google image of the throttle body holes, his is a standard body not the skunk as pictured.



also i cut off a piece of hose pipe and used it as a stethescope as i could hear an air leak, i listened to the inlet manifold and im sure i could hear a difference in sound from the belts side of the engine compared to the normal sound at the oposite end.

any advice would be good.

The hole on the top is actually for base idle and the IACV. Air goes in via the top hole and splits some going through the base idle screw and some going to the IACV. Base idle is ~500rpm so the ECU uses the IACV to get enough air in to maintain ~750rpm. If you are blocking the top hole and the car is not stalling then you have a vacuum leak somewhere as this should be the only place the engine is getting its air from when up to temp since you have blocked the lower hole and nothing happens (so the FITV has closed). You can spray carb cleaner around the inlet manifold/TB (anywhere there is a gasket or vac hose going in) and see if the idle drops a bit. Be very careful though as carb cleaner is flammable (Please don't use on a hot engine!)

^^ Like the man says. Bad IACV, vacume leak, or coolant leak (wich was the casue of my bouncy idle) which in return sucks air in.

Set the idle screw properly as per the service manual. IIRC with the IACV disconnected it should be 550-650RPM (rev counters usually read 5-10% high). If you can't set it correctly, or it goes funky after you reconnect everything, move on to finding a vac leak as above, although a can of air duster will do.

Failing that I recon the IACV could be bad.

ok. Thanks for all replies. Sprayed inlet with carb cleaner and car stalled. Held hand over throttle body and car nearly stalls but enough air is being sucked in the engine via the inlet gasket. Definate inlet gasket leak. Car being looked at on Friday for £100 as i do Not have time to do it. My mate rick thanks you all. As do i.

Mine also does this but not all the time. I dont have a fitv so it rules that out and ive also changed the iacv for a spare i had but it still does it. I also changed my complete inlet manifold and all gaskets and still the same. Any ideas. Sorry to jump in on your thread . Cheers jon

My lude also just started doing this I will try the above advice asap. Can this issue cause any potential damage?

I believe, a blown inlet (there are three suspicious gaskets here - the main one and the two gaskets surrounding the spacer) and/or exhaust gaskets (the main one and the one that connects the header to the downpipe) could *also* be a reason for such behavior.

You guys need to see what happens when you do this. If blocking the top hole does nothing there is a vacume leak somewhere.

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