Can't figure this out

[TexasTruck72]

I am not a newbie to bumpsides, but mine has started acting up as of the past couple days and I'm not sure what is going on . Would've posted this in another forum category, but like I said, I don't really know. Anyway, the symptom is a jolting/lunging of the truck while driving in normal conditions, especially when the engine is under load. I'll be going down the road and all of the sudden, the truck was start jolting two or three times, then resume normal. It happens every couple minutes or more. At first, I thought one of my plugs was fouling, resulting in misfire, but after changing all my plugs today, the problem still exists. The jolting feels like when you mash on the gas pedal and let off real quick, except all this is happening while their is constant pressure on the gas pedal. Not sure if this could be a carb issue or something else. Any input would be greatly appreciated. Thanks!

FYI:
My F-100 has a 360 V8 (2 barrel), 3 speed manual on the column, 2wd.

[chicof100]

Does your truck have the fuel pump with canister on it? Replace the filter in the canister. Most people don't know it's there so they install an in line filter closer to the carb. In the mean time the filter in the canister continues to get clogged.

[crazyhorse]

You could raise the hood with the motor running when it is dark and look for fire jumping.
If it is a manual choke you could pull the choke out a little to see if this helps.

Good luck.

[TexasTruck72]

Thanks chicof100 and crazyhorse for your replies. I thought about the fuel pump and or the fuel filter. That's something I'm going to check on today. Thanks!

[chicof100]

The fuel filter in canister should be C4AZ-9365-A Original part number Motorcraft part number is FG-1A

[1972hiboy]

Does this have petronix ignition?

[TexasTruck72]

Ok, I checked my fuel filter (which I replaced only 2 years ago) and it looked like new. Nothing clogging it up. My next guess is either something with the ignition or a vacuum leak? This could be causing my engine to surge while in motion or under load. Any guesses or ideas? I appreciate y'all's input. It's always great to get another opinion or set of eyes to look my question over. Thanks.

My truck's engine is still running points, no petronix.

[1972hiboy]

Ok, I checked my fuel filter (which I replaced only 2 years ago) and it looked like new. Nothing clogging it up. My next guess is either something with the ignition or a vacuum leak? This could be causing my engine to surge while in motion or under load. Any guesses or ideas? I appreciate y'all's input. It's always great to get another opinion or set of eyes to look my question over. Thanks.

My truck's engine is still running points, no petronix.

A vacuum leak would give you driveability issues across the board and all the time. When it acts up does the engine surge in power like the power increases then drops off or does the engine exhibit the symtom of more " momentarily" cutting out?? I would start inspecting your ignition stuff. good connections, points are in good shape. dwell angle is to spec. fwiw I have gone through four or five condensers in the past 4 years and when they went south they would cut the engine out.

[bluef250]

Any backfiring? If so, check distributor.

Check to see that fuel float is good.

[TexasTruck72]

Good news! My isn't acting up anymore as of tonight. I attribute this to when I removed the fuel filter this morning for inspection. I don't know for sure what the problem was, but I have a very good guess. My guess is that there was some small piece of debris that was trapped inside my fuel filter and under load(when the engine was sucking a lot of gas) was being pulled up and would partially block the fuel intake, thus causing a temporary loss in power. The temporary loss in power would allow the debris to sink back down, resulting in an opening in the fuel intake which causes a surge of gasoline; causing the truck to lunge forward. This all makes sense to me. The small piece of debris must have fallen out onto my driveway when I unscrewed the fuel canister and took the filter off for visual inspection. Gasoline dripped/poured out for at least a minute or so. Whatever debris was causing the problem probably was dropped during that time. Reason it wasn't until tonight that I noticed the truck was driving like normal is because I didn't start the truck until the evening after I had removed the fuel filter earlier today. Let's hope that took care of it! I'll let y'all know if the problem returns. Thanks again to everyone here on Fordification. Y'all brought some awesome advice to the table as usual. So great to have such a resource as the folks on this site!

[TexasTruck72]

Well, unfortunately, my bump is acting up again. I thought I had fixed the problem(and maybe I helped a little) but my truck's back to jolting again while going down the road. I spoke with a good friend of mine who has experience with these old trucks and he said immediately that it was a bad plug wire. Crazyhorse on here said the same thing last week when I first posted this thread. I believe now that it makes the most sense. I will check tonight for fire jumping. If I replace my wire set, does anyone have any good wire brand(s) to recommend for someone like me who is trying to keep a mostly stock looking engine. I'd like to replace my plug wires with new ones that are black in color, but the boots don't have to be(my existing ones are Belden 7mm with orange boots). Any suggestions? Thanks ya'll.

[Mctrick]

Check the distributor cap as it may have a hairline crack it and maybe shorting out across other plug wires.