71 El, 350

When ever I floor it at 25, 35, 45 etc M.P.H it hesitates big time almost to the point of shutting off, then I back off and it runs O.K. It has new spark plugs and a new fuel filter in the carburetor. At a stoplight it will idle smoothly and intermittently stumble and occasionally shut off. Could the two be related? The car is still new to me and it has a Quadrajet and an HEI distributor. Thanks to all!

I am not sure about the Quadrajets, but Holley has float adjustments. Make sure your equivelant is correct for the idle problem.
As far as stumbling or quitting when you get on it, make sure your timing is correct and your advance is working. Check the gas shot from the accelerator pumps. It must be large enough and come on as soon as the throttle plate starts to move. It should also inject right to the center of the venturi.

Hope this helps.
Dave

I know this topic is old, but I ran across it and thought someone else having problems might also.

I had this same problem and found it was caused by a vacuum leak.

First of all I hate quadrajets, they have always caused me nothing but problems, I threw it out the window and got an Edelbrock. I recently just put a new hei distributor in and my car would die while idling after abot 10 minutes of driving. It turns out it was a bad distributer. Threw a new one in and the car ran fine. Who knows?

[This message has been edited by 72SS_Scott (edited 01-07-2003).]

My symptoms were slightly different, (no problem at the higher speeds you mentioned) but my problem was the accelerator pump.

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I'd rather walk than be seen in a ford!

The first order is to check fuel pump pressure. You want to see a steady 4 - 7 psi when you crank the engine with the ignition disconnected, and you want to see a slow steady drop in pressure when you stop turning the engine.

Next, start the engine and let it warm up fully and then shut it down. Open the secondary air valve and release it quickly. It should snap closed instantly. If it doesn't snap closed, we'll go through the adjustment procedure for it later. Is the choke fully open, or is it still partially closed even when the engine is warm? With the choke butterfly fully open and with the engine off, look down into the primaries and open the throttle by hand a couple of times. You should see a couple of streams of fuel indicating that the accelerator pump is working okay.

Next, give it a good visual inspection for obvious vacuum leaks. You're looking for brittle and cracked vacuum hoses, and for open vacuum ports that should have something connected to them.

Finally, obtain a timing light and check the base timing. You should have it set around 10 degrees BTDC.


Q-jets are just fine as long as you know how to adjust them.

[This message has been edited by Randy Mosier (edited 01-08-2003).]