Ford 302 (5L) hesitation

Benzoid · May 24, 2010

I'm having a problem with my Ford 302 V8

It's hesitating a lot when I'm going slow (around town and such). It seems to run fine when i step on it and at cruising speed. There is also a sort of whistling or squealing sound that isn't belts. It's more like an air thing. Kind of hard to pin-point. That also goes away when I step on it.

I just changed the plugs, wires, cap and rotor. I'm thinking fuel system but I'm not sure where to start.

Also, I'm sure there are other things to check, but I'm unsure what those might be.

This is on a ford Pickup (not a van if that matters) I just figured you guys would be the best to ask. (other then the ford dealer

)

Thanks!

danthewolf00 · May 24, 2010

Check the vac lines could be a valve not opening all the way do to a crack and air bleeding in

highway star · May 24, 2010

Is this old enough to have a carb instead of injection? If so, there's an EGR valve behind the carb that can cause a problem. Take a screwdriver and work the plunger in and out a few times and put some grease on a q-tip to lube it up at the base of the plunger.

greg334 · May 24, 2010

What year?

If it is a 1972 ford P/U with a 302, it will be a different solution than if is a 2000 P/U with a 302.

Jack_Berry · May 24, 2010

tried the ford forum?

Ford Truck Enthusiasts Forums - Ford truck and SUV owners and enthusiasts Community And Information Source.

Benzoid · May 24, 2010

OOps.. Sorry I didn't put the year. it's a 93 with FI

I will check out the ford forums Jack. Thanks!

rollnthunder · May 25, 2010

The whistling could be coming from the maf sensor(mass airflow sensor) older model fords where prone to that.The stuble could be from a bad or dirty maf sensor.You can take them apart with a set of secure torx bits and use some mouth wash on a q tip to clean the really fine wire inside dont use to much pressure or u will break it.It gets dirty and can cause a stumble by any chance do you have a K&N air filter in it?If so the oil from the filter can add to this getting dirty.

Benzoid · May 26, 2010

rollnthunder said:
The whistling could be coming from the maf sensor(mass airflow sensor) older model fords where prone to that.The stuble could be from a bad or dirty maf sensor.You can take them apart with a set of secure torx bits and use some mouth wash on a q tip to clean the really fine wire inside dont use to much pressure or u will break it.It gets dirty and can cause a stumble by any chance do you have a K&N air filter in it?If so the oil from the filter can add to this getting dirty.

I don't have a K&n on it but I will take a look at the MAF Sensor.

Thanks! and I will let you know what I find.

stamp11127 · May 26, 2010

Sounds very similar to the problems I've had with my F250. How does it run when cold? Mine doesn't have the problem as bad until the computer switches to the warm run condition.
Since you can hear a whistle while driving the first thing to look at is the brake vacuum booster. Mine leaked and you could hear a hiss right after the engine was turned off. Once that has been checked/replaced I would get the ol' can of carb cleaner out and search for an additional leaks at the fittings on the engine.
One area that has been known for problems is vacuum canister on the passenger wheel well. Looks like a black coffee can with vac lines going to it.
Another point for hesitation is the throttle position sensor. Some of the Ford forums have stated that new imported ones can give problems and to stick with the Motorcraft brand. Sounds crazy but the guy said you can see the difference with an oscilloscope. And it may be what is goofing up the ecm. That is my next change, going to dump the cheap import part. I've gotten most of the hesitation out but still have a slight skip from idle to 2000rpms.
Spark plug wire routing is important on this engine. Found out the hard way. The passenger side wires need to run in front of the valve cover and not over the top. Even though the egr pipe is insulated it will burn through the wire. Lesson learned.