my truck has started to fluctuate rpms at slow speeds of around 25-35 mph, about 200 rpm drop, then pops back up. this is a new to me truck. It has 224,000 miles on it. replaced the fuel filter, when I had it tuned up awhile back, 6 months ago. I don't drive this truck everyday as it is for ice fishing and maybe to pull my atv trailer, but also gets ****ty gas mileage. any help would be appreciated. thanks

 

I'm not an expert, but I had the same problems, but I noticed the engine running rough when idling, it was the intake gasket/manifold. My gas mileage was like 10 mpg, afterwards I got around 16 mpg, that is my 2 cents.

 

Have you changed the plugs and HT leads because that's the first sign of a break down in them.