Fast Idle
 

Hello Everyone!
I have a 1969 mustang that I am completly rebuilding and just recently put a 302 that I rebuilt in. The engine runs fine but it idle's to high. I completly turned the choke to the lean postion, and back off the idle screw all the way. I even removed the pins on the electric choke so I could turn the choke down even further. When I lower the choke the idle does lower but not enough. The engine is a high performance 302 with a comp cams extreme energy cam and 9.5:1 compression. The carb is a Holley 670 cfm with an electric choke. The car was on my 1969 cougar with a high performance 351 Cleveland and ran good. Do you think that my electric choke might have gotten screwed up. or maybe I need to put smaller jets in it. I am not sure if the guy who originally owned the cougar rejetted the carb so it could handle the engine. Any advice is greatly appreciated.
Thanks alot
Matt

Re: Fast Idle
 

Are throttle plates completly closed?? All four of them??

How "High" is high idle??

Sounds like maybe the back barrels are open a crack. Check it out and post back.

Re: Fast Idle
 

I will check the throttle plates today. As far as the idle goes, I can get it at best around 1000 rpm's in park. What should I do if the throttle plates are slightly open. Is there some sort of adjustment?
Thanks alot

Re: Fast Idle
 

If the plates are sticking, find what is causing it and unstick them.

The secondary plates have an allen screw adjustment for the stop on closing. You have to remove the carb to adjust it.

Re: Fast Idle
 

Hey,
Today I checked, and they dont look like they are sticking at all, The secondaries are completly closed. I noticed that the idle will vary. Sometimes it will be high, and then I rev it a little, and it drops down, and when it is really low, I rev it and it raised the idle. Sometimes it does it when I dont touch anything. The rpms are just all over they place when ever they fell like it. It seems like something is sticking or the electric choke is kicking on and off. Do you think that it is the choke.
thanks alot
matt

Re: Fast Idle
 

Timing.

Vacum leak.

Re: Fast Idle
 

Vacuum hoses swapped? Full time vaccum hose on the distributor advance...

The choke shouldn't be a problem if the engine is warm... the choke plate should be wide open, and the fast idle screw shouldn't be touching the cam.

Re: Fast Idle
 

I checked to make sure that the vacuum lines are all in their proper place. I did not hook up any of that emissions stuff, only the brakes, pcv, trans and distibutor lines back up. When the car is fully warm it is still idling high and the rpms dont change from when I start it and when it is warm. I retarted the timing and it lowered alittle bit but not enough. I have the idle screw off all the way and still it doesnt help. If I turn the choke all the way down past where the pins on the cover were the car will try to stall even when it is warm and if I turn it on alittle more then that the idle starts to race. I know that there is a fast idle screw that is located on the bottom of the choke housing. Will that do anything if I adjust it.
Thanks alot
Matt

Re: Fast Idle
 

The fast idle screw rides on a cam connected to the choke flap. If the choke flap is all the way open, the screw should not be touching anything. as when it IS touching the cam connected to the choke, it will increase the idle as it takes over for the normal idle screw.

The idle mixture screws should be turned all the way in until the idle drops off, then it should be backed off by 1/4 turn.

The float should have the gasoline level even with the sight plug bottom.

Re: Fast Idle
 

BTW... adjusting the choke to a leaner position (open) when it is warm should not change anything in the idle. It will speed it up as the choke plate closes, and eventually flood the engine as the choke is fully closed, leaving the engine in too rich to run.