92 F150 4.9 skips

I have a 92 F150 2wd AT 4.9L with 253,000 miles that skips when driving 35-45 mph under no/light load. Hit the gas, runs normally. Have swapped Throttle Postion Sensor, plugs, wires, cap, and rotor. Cleaned air intake and associated parts and used a couple fuel cleaners. Has been an issue for the last several thousand miles. Truck runs great otherwise. Appreciate your suggestions. Thanks!

You need to run error code scans but I'm leaning towards MAP sensor. but it could be a few things.Equus Innova 3145 OBD-I Ford Scan Tool (http://www.handsontools.com/Equus-Innova-3145-OBD-I-Ford-Scan-Tool_p_5574.html)

Thanks for the reply. No codes registered due to this issue. Not sure if MAP Sensor has been changed, but will look at that. Pulled Distributor to check gear mating and "sloppiness" - all good. Wondering if I could have a scorched valve - #5 cyl burns different than rest.

MAP Sensor no help.

Thanks for the reply. No codes registered due to this issue. Not sure if MAP Sensor has been changed, but will look at that. Pulled Distributor to check gear mating and "sloppiness" - all good. Wondering if I could have a scorched valve - #5 cyl burns different than rest.
But you have codes?

Welcome to the forum!

With that many miles a scorched valve could well be the problem. Under a light load the valve leaks, but when you give it gas and a heavier load the valve will seal up due to higher cylinder pressure. Not to worry. It could be the result of deposits on the valve itself. My suggestion......and there may be those that disagree.....put a quart of Marvel mystery oil in the crankcase and put 8 oz. of the same in a full tank of gas. Marvel Mystery oil. contains lubricated solvents which will clean up the valves and make it run better. I'd try this before shelling out $1500 for a valve job.

try unhooking your egr vacuum line and recheck it. i suspect that you have a bad egr valve and or clogged egr ports. the egr system is the only system that functions only during those types of driving conditions