In my '85 F-150 4x4 with a 351W 4v H.O., with a Holley 4bbl carb, I have this interesting problem with it trying to stall out when I lightly press the accelerator while the engine is below normal operating temperature. The problem usually goes away when the engine gets warmed up, but not always.

If I give it more than about 1/4 throttle, it doesn't stall, but usually when I'm driving through parking lots with a cold-to-warm engine, I give it less than 1/4 throttle. When I do this, it acts like I'm not pushing the gas at all, and will sometimes stall completely out.

The carb looks like it may have been backfired through, as it has a lot of black buildup in the main body, so I'm wondering if it might be a power valve problem? I know backfires destroy a power valve faster than you can spit... Could this be the problem?

I had always thought power valves were more for WOT (wide open throttle) useage, but I could be wrong. I know how to rebuild a Holley, but I still don't know everything about them.

The only other thing I can think of is perhaps an ignition problem. It's not a really major problem, as I can tap the gas a couple times to get it to go rather than giving it too much throttle, but I'd rather fix it rather than "just get by".

Any ideas from you folk out there would be greatly appreciated.

 

I'd check your acclerator pump, and make sure your choke is working/adjusted properly.

 

When you press the pedal the throttle valve opens a little, the accelerator pump is supposed to give a squirt of fuel so the air/fuel mixture isn't out of line. Apparently it isn't. Turn it off, stick your head over the carb and move the linkage....any squirt?