idle fluctuation

onefastmustang · #1 (**permalink**) 05-09-2009, 02:15 PM

My webers are running the best they have ever been except for one thing.. When the car is cold it idles perfectly, once it warms up the idle seems to rise up a couple hundred RPM.. thoughts on this? Should I just lower it a bit more so it's a bit rougher cold?

MaSnaka · #2 (**permalink**) 05-09-2009, 03:31 PM

Do you have a vacuum advance? I had the symptom of higher rpms when warm and I recently discovered on my holley carb that I was getting a slight vacuum when I shouldn't be, hence causing the timing to advance and raising the idle. A quick jab at the pedal would bring the idle back down. I haven't resolved that issue yet because others have crept up, but thought I would share incase it helps you.

John

onefastmustang · #3 (**permalink**) 05-09-2009, 05:58 PM

No.. I have mechanical advance only.

Rick Parker · #4 (**permalink**) 05-09-2009, 07:11 PM

Clearances "loosen" up with temprature, normal...mine does the same thing.

onefastmustang · #5 (**permalink**) 05-09-2009, 07:26 PM

So what you are saying is I should turn the idle down and live with it...

So what's a good idle to have when warmed up? 800?

Rick Parker · #6 (**permalink**) 05-09-2009, 07:51 PM

The cam will dictate the idle to some extent but 800-900 RPM approx. The adjusted idle & idle mixtures should be done with a thouroughly warmed up engine.

Gaz64 · #7 (**permalink**) 06-28-2009, 03:07 AM

I've yet to see any carburetted engine idle at the same speed hot AND cold.

As others have said, adjust idle speed at operating temperature to 800 - 1000 rpm depending on your cam.

More than likely it won't idle well cold, just something to live with.
Better than a hot motor that won't shut down.