Fast idle, In search of air leaks |
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Fast idle, In search of air leaks |
Rand |
Jan 25 2006, 05:54 PM
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#1
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Cross Member Group: Members Posts: 7,409 Joined: 8-February 05 From: OR Member No.: 3,573 Region Association: None |
Been trying to nail the fast idle problem for a while. Have absolutely ruled out any vacuum leaks above the throttle body. Have replaced the injector seals. That leaves me with.... Leaking around the butterfly in the throttle body? Or somewhere else in the plenum or intake runner seals?
If I put my palm over the air intake, it does choke it down. That makes me wonder if air is getting around the butterfly (since the idle air adjustment screw is all the way closed). But I'm a noob on this detail... Please comment on this!! I would think a crack in the plenum / air distribution box (whatever you wanna call the air box under the throttle body on a '75 2.0 Djet) would be rare. But I'm down to checking rare things on my list. I guess I don't mind taking all that apart because I haven't been there yet and wouldn't mind painting the plenum and air intake tubes anyway. Sooo.... Anyone have photos of disassembled plenum, intake runners, etc.? What will I need if I take this apart? (Seals/gaskets? Anything else?) |
Rand |
Jan 26 2006, 03:01 PM
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#2
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Cross Member Group: Members Posts: 7,409 Joined: 8-February 05 From: OR Member No.: 3,573 Region Association: None |
The vacuum hose between the plenum and MPS is good.
I don't think my 75 has a PCV valve. I'm not sure which models had or didn't have them. But if I completely plug the port where the oil breather hose connects to the airbox, idle doesn't drop. So I don't think that could be it in my case... unless there's something else I don't understand about how the PCV valve could affect idle. With the idle-air adjustment closed tightly, and the butterfly squarely closed, it's still sucking pretty hard when I put my palm over the opening. Blocking it pulls the idle way down below normal and makes it stumble. Is it normal for that much air to still be getting past the closed butterfly? (Before anyone asks... no, I don't run it without the air cleaner! Except that few seconds just long enough to block the throttle body intake to see what happened to idle. (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif) ) |
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