Idle still too high

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Oct 14, 2002 | 06:20 PM

WrenchHead84

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From: Warrenton, VA

Idle still too high

My idle is still around 1000 rpm's. I've taken my carb off and looked at the butterfly valve. Nothing is catching, or preventing it from closing. My high idle is not interfering with my curb idle, and my curb idle screw is so far back it's not even touching the throttle lever. My choke is fully open at warm up temps. According to the chiltons manual I think it says 700 rpm's at curb idle.
Any ideas would be helpful...
WrenchHead

1979 F-150 Custom. 302 V-8 4-spd 2WD. 126,200 Miles

Oct 14, 2002 | 06:37 PM

71swissaqua

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From: Huntersville

Idle still too high

Is your timing way advanced? I've noticed on mine if I advance it sometimes I have to back down my curb idle.
Clint

Oct 14, 2002 | 07:22 PM

airharley

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From: Escondido, CA

Idle still too high

What kind of carb are you running? You could have the butterflys sticking open from the throttle return spring not having the correct amount of tension on it. Also look down the top of the carb and see how much gap you have in the butterflys. If you have more then 1/16 of an inch gap you are off of the idle cicuit and the air rushing by is sucking the fuel out as if it were driving down the road. Just don't check the butterflys while the engine is running.

Oct 14, 2002 | 07:30 PM

Bronco408w

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Idle still too high

Oct 14, 2002 | 08:52 PM

WrenchHead84

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From: Warrenton, VA

Idle still too high

My timing is at 6 degrees BTDC. As far as the return springs go, they are a suspect. I can put pressure on the throttle lever and force it down to maybe 800 rpm's. I'm going to try to get new springs soon. If that doesn't solve it....man oh man. I can check the butterflys, but when I had it pulled off, I checked that anyways. It appeared to be fine.
WrenchHead

1979 F-150 Custom. 302 V-8 4-spd 2WD. 126,200 Miles

Oct 14, 2002 | 10:53 PM

airharley

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From: Escondido, CA

Idle still too high

What you are looking for is the .025 wide groove that is cut into the bottom of the carb bores. If the grooves aren't visible with the throttle closed then you are past the "Idle Circuit" Look for a bent linkage rod or partically open secondaries. The secondaries shouldn't have any gap between the butterfly and the wall. I know a lot of stuff to look at closely. What may help is knowing exactly what carb you are running. ie... Holley, Edelbrok, Carter, FoMoCo, Demon, or Rochester QuadraJet and the cfm if you know it off hand.

Oct 15, 2002 | 10:56 AM

WrenchHead84

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From: Warrenton, VA

Idle still too high

The carb I'm running is the stock motorcraft carb, but it was rebuilt by holley. I'm not sure what the cfm is on the stock carb.

WrenchHead

1979 F-150 Custom. 302 V-8 4-spd 2WD. 126,200 Miles

Oct 15, 2002 | 07:25 PM

WrenchHead84

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From: Warrenton, VA

Idle still too high

Found the Problem!!!!

I looked at a vacuum diagram...finally...and found an incorrect routing. The distributor was basically getting full vacuum right from the manifold, leaving it at full advance the whole time. I corrected the lines, and it now runs fine. As far as a vacuum leak goes, it would normally slow the idle...I believe.

WrenchHead

1979 F-150 Custom. 302 V-8 4-spd 2WD. 126,300 Miles