I'm running a holley 670 street avenger with an electric choke on my 350 sbc. It's been idling super high, around 1,100 and up in gear and then in park or neutral its at a bout 1,500. Needless to say this is a problem, I've tried to adjust the idle screw but it has little effect. On the way to Mooneyes it was idling at around 500-600 and almost staling, but at the end of the day went back up in the 1,000s. I' figure the choke is malfunctioning because it does not drop the RPMs down after it warms up. Any ideas?
Is it a newer carb? I ask because an older worn out one might have worn throttle shaft bushings. that would cause a vacuum leak, and the throttle might hang up intermittently. Do you have a strong enough throttle return spring on the carb? Is your gas pedal secure and free of obstructions? Linkage or cable operate smoothly?
spray wd40 around the manifold and see if the idle drops or sputters, that will tell you if you have a vacuum leak. sounds like the leak got worse as the day went on.
Spray carb cleaner near the carb base, intake manifold gasket to head area, and throttle shafts. If it changes rpm sitting with no action of the throttle then its a vaccum leak and where you squirted is where the leak is. Avoid overspray down the carb, that will change the rpm also. Just the way I would go about it.-Weeks
Thanks guys, i'll try all these. desertratrodder, it's about 9 months old, so its pretty new. I'm running a two consecutive return springs. and everything is secure and free of obstructions.
If the electric choke pod is "wound" too tight it will not allow the fast idle cam to come down to base idle. If all else checks out mark the current position and then try to go looser on the tension.
My roadster will do that from time to time. Every once in a while the secondaries will creep open just enough to make it idle too fast. It acted like it was stuck on fast idle but it would never kick down. I spent lots of time chasing a choke problem. I have to pull over and manually seal the secondaries. Then you can hear the cam lope. I hate the muscle car look of the carb and I have never got into fixing what ever is wrong with the linkage. It will be fine for weeks and then just when you are pulling into the fairgrounds it will idle way up. Check the secondaries to see if the extra fuel and air are coming from them.
A lot of choke sticking/idle speed problems can be fixed with a few drops of lube on the choke linkages. In the era when carbs ruled, it was part of a quality tune-up. Pretty much a lost practice anymore. good luck
If your car has an automatic it could be a vacuum leak at the modulator.it wont show a vacuum leak at the carb.pull the hose of the carb and plug it off.check to see if it still idles high.if it does,change your modulator on the trans.i wouldnt drive it cause you have to bring it to a high rpm to ever get it to shift(wait a minute, i always shift at a high rpm!!!).just a thought cause i had on drive me crazy like that.
Disconnected the choke and made sure the choke gate stays open, solved the problem and it's running better than ever. Idling at 800 in neutral and about 650-700 in gear.... you can fully hear the cam, sounds real bad!
The best and easiest check for a vacuum leak is, take the air cleaner off with it running, place your hand over the top of the carb to choke off some of the air. If the idle smooths out and picks up, you have a vacuum leak. It if tends to die out, you probably don't have one.
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