Hello I am new to this forum. Was wondering if anyone might give me a point in the right direction to fix my problem. I have a 1991 4WD auto. with the 318. It has 168,000 miles and has run like a top until about 3 weeks ago. Ran great on a Friday and like crap on Saturday. The idle seems to flucuate and go from almost stalling to 300 rpms above the usually idle. It will even out for a bit and then do it again. The truck never stalls though. When the truck is at a stop sign it seems like the wheels are trying to over power the brake. In the gravel the tires spin alittle when switching from Reverse to Drive. The truck will run but is slopping in throttle response. When you get up to 40 to 45 mph the transmission seems to switch back and forths between gears. I have done a tune up replacing rotor and button, plugs and wires with no improvement. I also cleaned the throttle body. I was wondering about the Throttle Positioning Sensor, I can see it causeing the fluctuating throttle but wasn't sure if it would cause the gear switching at 45mph. Should the TPS be the next step or is there anything else I should look at next. Thanks for any help.