1996 F350 with an occasional miss?

My 1996 F350 is a crew cab dually 4x4.
She's got the big gasser 7.5L 460. I bought this truck 9 months ago with an occasional miss. Very nice and hard to find truck, has 125k miles.

The miss is at random times, any rpm. It trembles while idling, can miss while driving and when i get on it a little hard from a light. But it's not constant, could go for hours without a miss.
Distributor cap, plug wires, plugs, IAC sensor, throttle position sensor, fuel filter, fuel pump relay are ALL NEW. I tested for spark on each wire when i put in the plugs. The fuel pump runs fine and for the correct length of time prior to start. I have the problem on both the front or rear gas tank.
I've replaced just about everything i can think of. Hopefully the timing isn't off, but it had good spark.

What other things could cause the miss?
Thanks guys.

paul h2015-03-05T12:05:59Z

Could be sticking/dirty/partially clogged fuel injectors not giving a good spray pattern at times...try running some Seafoam or Techron in the fuel tank per label directions (usually 1 ounce per gallon) for a couple tanks to clean the fuel system/injectors and see if it improves. May need the injectors professionally inspected for good spray pattern/cleaned. Given the mileage, they could be due for a good cleaning.

Could also be a minor vacuum leak causing a misfire at times...check all vacuum hoses for cracks splits, looseness, etc.. Spray around vacuum port fittings with carb spray with engine idling...rpm's rise or alter indicates a leak.. Check for air leaks/cracks in air intake ductwork or leaks around TB or intake manifold mounting/sealing areas...spray around TB mounting / manifold to head sealing areas with carb cleaner while engine is idling...if rpm's alter, that indicates a leak. Check electrical connectors for engine sensor harness/injectors for corrosion, looseness, terminals backed out of connectors, etc...

Random misfires can be hard to track down so just try to eliminate as many possible issues as you can.

Any check engine light? trouble codes?

00

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