1992 Other GMC Models V8 Two Wheel Drive Automatic 250000 miles
I have an old cargo van (a GMC Vandura) - needs to be replaced, but it's all I have for now. It's in good condition for its age and use, but the accelerator is messed up. First, it's very slow to accelerate, perhaps getting to 30 mph in around 10 seconds. Second, my speed seems to top out at 50 mph on the interstate. I slow down as I climb a rise and use the subsequent decline to get back to speed. It seems to rev at three speeds, all of them ineffective. If I try to speed up too quickly, sometimes it pops at the tailpipe. Intermittently and rarely, it'll start working fine and I'll be able to accelerate with ease, but it never lasts very long (and I might be wrong, but it seems to happen more frequently when it's cold). I've recently had the fuel filter replaced - it was apparently very dirty - but that didn't help.
I truly hope it's not the transmission (can't afford even a used one at the moment), but if it is, is there something I can do short of replacing it?