I have a 1996 F250 XL with the 460 and 5 speed manual transmission, 4x4. The other day I was out on a pretty rough gravel road, and hit a really bad series of bumps that shock the truck up pretty good. After that, I notice that the engine feels like its bucking when the truck hits bumps now. Here what happens now when I hit a bump:

- engine "bucks", or feels like it is cutting in and out as if someone were pushing and releasing the gas pedal rapidly;
- speedometer and tachometer needles bounce up and down while the engine is doing this.

It will do this in any gear, and seems to only happen the the truck hits a rough spot of the road/speed bump. The truck seems perfectly normal when on smooth roads and idles fine; nothing else seems out of place. It feels like a wiring issue: some harness or connection knocked out of place. Any ideas?

 

I'd check the rotor and cap and all of the plug wires.

 

I'd check the VSS and all the connections related to it including the PSOM.

 

I'd check your fuel level. I've had this happen when I was real low on fuel and the little bit that was left was sloshing around, so the pump was sucking air.

 

Thanks for the suggestions; when I'm back at home I'll try these out and let you guys know what happened. Hoping for a simple cheap fix!

 

Truck died on me today, after some rough running and backfires. Looked under the hood and found the bracket holdig the ignition coil and some other important components was loose, probably from the rough roads. I will check those parts out and replace the coil, and see how she goes.

 

Sounds like you found the problem.