javatrooper

I just put a '94 302 longblock into my '84 F150. Used the '84 distributor and intake and carb.

I have a miss that I couldn't track down so I bought a good multimeter that has a tachometer. Pulled each spark plug wire and noted the difference in RPM.

Base RPM was 460. Four of the cylinders had RPM drop to 410-420 indicating working cylinders. The other four had the RPM rise to 520 when the spark plug wire was pulled. What does that mean? To add to the mystery, it runs in pairs in the firing order. 2 have rpms drop, followed by 2 where rpms will rise. Not sure where to go from here? Warped distributor?

For sure the wires are on the right plugs. New plugs, wires, dist cap and rotor.

slash09

Are you SURE the wires are on the right plug? Pulling the wire shouldn't make rpm's rise at all. What are the cylinder numbers on the ones that rise and the ones that fall? From the front back on pass side is 1234, and 5678 is drivers side, front to back. firing order is 15426378. Double check to be safe.

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javatrooper

I had the firing order set 1-5-4-2-6-3-7-8. But a tech from 2 car pros suggested I try a modified firing order 1-3-7-2-6-5-4-8 and I'll be dammed if the truck didn't fire right up. In fact it seems to run even better but only in neutral. Idles fine and revs up great. Took it for a test drive and if I gas it the engine nearly dies and then slowly gains rpm, but is basically powerless. So today I pulled plug wires again. Now rpm rise on all cylinders as follows: Base rpm is 570-580. 1-600 rpm, 3-600 rpm, 7-600 rpm, 2-630 rpm, 6-600 rpm, 5-600 rpm, 4-620 rpm, 8-630 rpm. This leads me to believe my firing order is still not right.

pass front to back 1-4 drivers front to back 5-8, dist counter clockwise rotation.