Slightly fast idle - suspect AAV, Am I right? Options

[gturner008]

Owned 76 2.0 for two weeks now.

Lots of little jobs completed. But I have an idle that’s 1100 rpm. The idle screw is virtually fully in.

I suspect the AAV is stuck slightly open when engine hot. If I pull the tube from the air intake and put my thumb over it, the revs drop to about 600 rpm.

Everything else is good. All hoses correct and no leaks.

Am I right in thinking the AAV should close up completely?

If it’s a stuck AAV, any recommendations for getting it freed up?

Cheers. Gary

[BeatNavy]

Fast idle is normally caused by vacuum leak and/or timing too far advanced. The AAR/AAV is essentially a managed vacuum leak. Yes, the AAR should basically close off all the way. But if you plug that hose and your idle drops to 600 -- that's too low and something else is going on (or I guess you need to open air bypass on throttle to compensate if you have it fully closed off).

Take the AAR out. You can test it by grounding the base and carefully attaching the lead to 12v. You can look inside and gradually see the valve close off over the course of 5 to 10 minutes. If it's sticking, spray PB Blaster in there and let it soak for a while before shaking it out. Try that a couple of times. If that doesn't work, you can try to carefully pry open the can, take it apart, and give it a more thorough cleaning from the inside. Try not to break the wire lead as those are pretty fragile after all these years.

Good luck, Gary.