jodysgarage

Just bought a 1990 F150 w/ 5.0 302 Auto Trans and 132,000 miles.
I have really tried to give it some TLC since it had been neglected.
New oil (high mileage syn blend), antifreeze flush, new plugs & wires, PCV valve, air filter, new front dif/rear dif/ transfer case fluids, and I have been using gas treatments for the past few tanks.
It had been running really smoothly until yesterday.
When I crank it, it revs a little high the first few seconds which is normal.
Then it goes from normal idle to revved and back again like it has a mind of its own.
Even driving in the first few minutes it was surging periodically like the idle was revving on and off- especially when I had my foot off the pedal and was coasting.
It was rough- I thought it was my transmission at first.
It did seem like it stopped after the engine was hot, but I did not drive it long, so that might have been coincidence.

Anyway, I thought I had this baby running good and now I am stumped.

Any idea of what would cause this?

Also... any other preventive maintenance you would do?
Besides above, it has a new battery & alternator, tires & brakes.

Thanks so much and I have enjoyed reading these forums!

JodysGarage