Idle Speed High

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    The odd part is, it idles just fine at a lower RPM. The problem is when I put it into gear. I don’t need the higher idle speed to keep it running in park, I just need it so it doesn’t die when I put it in gear. 

We did a vacuum check on Sunday and it was reading 12. I also sprayed carb cleaner around the carburetor, intake, and all vacuum lines. Didn’t seem to have a leak anywhere.

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WhatISit Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Aug/07/2017 Location: Phoenix, AZ Status: Offline Points: 0	Post Options Post Reply Quote WhatISit Report Post Thanks(0) Quote Reply Posted: Dec/19/2017 at 1:06am
	The odd part is, it idles just fine at a lower RPM. The problem is when I put it into gear. I don’t need the higher idle speed to keep it running in park, I just need it so it doesn’t die when I put it in gear. We did a vacuum check on Sunday and it was reading 12. I also sprayed carb cleaner around the carburetor, intake, and all vacuum lines. Didn’t seem to have a leak anywhere.

needafasterAMX Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Feb/20/2008 Location: TLH,Florida Status: Offline Points: 724	Post Options Post Reply Quote needafasterAMX Report Post Thanks(0) Quote Reply Posted: Dec/19/2017 at 1:28am
	The problem , probably is not one thing, but a few little things. I had the same problem that you describe., 15 internal timing was all i could get out of mine, if this is a stock low compression engine , shoot for 38 total. if you are using the cheap gas. You may have to change your vac advance can to help with your idle. The biggest help on mine was putting the right PCV valve in, If you have a silver tin can PCV valve and not a stock steel black one , believe me , it would be worth it to source one. you can still get them at your local auto store, may have to order it in. Edited by needafasterAMX - Dec/19/2017 at 1:31am
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WhatISit Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Aug/07/2017 Location: Phoenix, AZ Status: Offline Points: 0	Post Options Post Reply Quote WhatISit Report Post Thanks(0) Quote Reply Posted: Dec/19/2017 at 3:42am
	I’ll have to check that out. I have about 9:1 CR

WhatISit Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Aug/07/2017 Location: Phoenix, AZ Status: Offline Points: 0	Post Options Post Reply Quote WhatISit Report Post Thanks(0) Quote Reply Posted: Dec/19/2017 at 1:26pm
	OK, so here's an update: I heard of others checking the idle in neutral to see how it runs to help evaluate whether there's a vacuum leak. So I got the engine warmed up, and slowly turned down my idle speed until I got it all the way down to about 550 RPM--it ran fine without even stumbling. Might have been able to go even lower, but I didn't bother.

DaemonForce Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/05/2012 Location: Olympia, WA Status: Offline Points: 1070	Post Options Post Reply Quote DaemonForce Report Post Thanks(0) Quote Reply Posted: Dec/19/2017 at 3:46pm
	This problem sounds like the issue I have going on with every Ford pickup that wants to run wild at a dead stop but there's no more idle screw to back off and there are no vacuum leaks. What kind of RPM drops do you see now?
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WhatISit Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Aug/07/2017 Location: Phoenix, AZ Status: Offline Points: 0	Post Options Post Reply Quote WhatISit Report Post Thanks(0) Quote Reply Posted: Dec/20/2017 at 1:53am
	I didn’t attempt to put it in gear to see what would happen, but I’m sure it would have died. That’s why I have to manually raise the idle speed to about 1400-1500 in park/neutral to keep it running when I put it in gear. It drops a good 600 RPM or so when put in gear. Wants to be at about 850 when in gear. That’s why I’m thinking it’s pushing against the tight torque converter and dying. I’m assuming the engine load is killing the engine at lower RPM—because the converter is trying to lock up to some degree. Edited by WhatISit - Dec/20/2017 at 1:56am

Boris Badanov Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Dec/14/2013 Location: NH USA Status: Offline Points: 4210	Post Options Post Reply Quote Boris Badanov Report Post Thanks(0) Quote Reply Posted: Dec/20/2017 at 5:35am
	Low compression at idle speeds makes for a cascade of minor problems that become a pain in the rump. As a result of late intake closing ("hot cam") you have poor vacuum at idle. This results in poor idle fuel control and compounds the problem. More ignition timing at idle will help, but the danger is detonation at high engine speeds. Restricting the total advance in the distributer and setting more initial timing should solve the problem with no danger of detonation. Hooking the vacuum advance to a untimed vacuum source with stock initial timing has worked for me. That is hooking it directly to the intake or any constant vacuum source.
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Lyle Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/17/2014 Location: None Status: Offline Points: 772	Post Options Post Reply Quote Lyle Report Post Thanks(0) Quote Reply Posted: Dec/20/2017 at 7:52am
	After reading this all over and your idle settings I'm thinking that your mechanical advance is cutting in way too soon. Between setting idle (fixing with the mechanical stop) at 1100 to 1400 and your idle drops, if it's not vacuum then your mechanical advance has already moved at this RPM and allows less advance and lower RPM when put in gear. Mechanical advance should be set to start near 1500 RPM and end at 3500 RPM. Might try locking out your mechanical advance to set idle and see what happens.

WhatISit Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Aug/07/2017 Location: Phoenix, AZ Status: Offline Points: 0	Post Options Post Reply Quote WhatISit Report Post Thanks(0) Quote Reply Posted: Dec/20/2017 at 12:40pm
	Wouldn’t a vacuum or timing issue make my car not able to idle at a low RPM. at all? I had it down to 550 and it was fine.

Lyle Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/17/2014 Location: None Status: Offline Points: 772	Post Options Post Reply Quote Lyle Report Post Thanks(0) Quote Reply Posted: Dec/20/2017 at 2:33pm
	That's why I'm now thinking is is likely not a very large vacuum leak. But the idle switch at approximately 1000 RPM? Steady idle should not jump here so if you can idle down to 550 then something is allowing the idle shift. Fuel or ignition advance and I'm inclined to think mechanical advance jumping in and out where it shouldn't. Easy enough to rule out. Plug the vacuum advance and set the steady idle to 700 RPM or so. Then slowly throttle up to 1400 RPM. There should be no change whatsoever in timing. Edited by Lyle - Dec/20/2017 at 2:51pm