Thread: Vacuum leak?

OK so my car has been idling a bit high for the last week, and I haven't had time to adjust it. I got up today and started turning the AAC screw to lower the idle, and I ended up closing it completely before it would idle at about 800 RPM. Shouldn't the engine die if I close that valve completely?

The problem is that now the engine feels horribly sluggish, and if I push in the clutch at about 4,000 RPM and just let it idle, it dies unless I rev the engine. Sounds like an intake manifold vacuum leak to me, but I wanted to check with you guys.

How would I go about locating the leak? I tried spraying water on the vacuum hoses, but the idle would never change. I'm going to try it again later with the engine cold...

It's not actually a valve, just a valve controller, and I think it's only supposed to be able to adjust like 100 RPM (according to FSM) so I don't think it's possible to kill the engine with it. But 800 is still higher than spec (750) especially if you had to clamp it all the way down. You're supposed to be able to tell if there is a leak by pinching the air regulator hose and seeing if the idle drops. If so, there isn't a leak (after the TB).. I don't know how realistic that is since if it's a small leak you might not notice. Easiest way is probably just to go through and check all of the vacuum hoses by eye for leaks.

There's one about pinching the PCV hose too. The idle is supposed to stay constant if you do that, otherwise it indicates a leak. Pretty sure that's what it is but not 100%.

Another way I've heard of but not tried is spraying starter fluid around different hoses while the engine's running. If it leaks in somewhere then the engine will rev a bit.

Thanks for the tips on finding those leaks - I was actually taught to spray water, and see if the idle drops instead of rising, that way you're not messing around with starter fluid in a hot environment

Thanks again,
Rick

800 is not higher than spec. Spec is 750+-100. Its known that factory spec is too low. I try to get my cars to idle 850-950 because it keeps oil pressure up a bit.

Did you reset the ECU? Pull codes?

Also that screw will not let the engine die. You can try cleaning you iacv assembly and checking your pcv valve for starters.

OK cool I'll definitely look into that on Thursday when I get some time on my hands.

Thanks guys!