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1994 Ford F-150, acceleration interuptions, pops

Ford F-150, 1994:
intermittent problem. going down highway, foot on the gas.
at times, will press accelerator to go faster but nothing happens, like clog somewhere.
sometimes, with foot still on gas, i will hear a popping sound coming from under the truck, (under the engine?, or drivers seat).
Usually 4-5 pops, sometimes none. But after each pop, car accelerates slightly, as if it is a slight clearing, until finally, as if some clog was opened up, the car plunges forward, so i then take my foot off the gas.

sounds like either problem with fuel getting to the engine or a problem with the exhaust.
any ideas?

The first thing I would suspect is the timing chain. Your vehicle is at an age and design where the timing chain could cause this type of problem.


thanks for the comment, but the pops sound like they are coming from the bottom of the truck, not inside the engine.

The pops could be in the exhaust and due to an engine performance problem. There are a number of things that could cause something like this but not enough technical info is known to be in the ballpark with any guess.

Fuel pump breaking down, exhaust system restriction, or ignition miss possibly related to the ignition module are a few of them. This truck should be a TFI module version so those units are always suspect due to a history of heat related failures.

Some diagnostic procedures might involve a vacuum check, fuel pressure test, check for any codes, and so on as a starting point.

these are good ideas. thanks much.

I know that the fuel pressure is lower than it should be. (was checked recently). Also, it did this 4 years ago, --I took it to a mechanic and he fixed it. I brought it back to that same mechanic and he cleaned out the fuel system and put on a new fuel filter, but it did not prevent the problem–in fact it made it worse.

The exhaust system is a little beat up and I had thought about that as a candidate–but that has not changed since I have had the truck, so probably not it.

I may take it back and have the fuel system looked into more. I will ask him about the ignition module.

thanks again