1992 Other GMC Models accelerator problem

PANDARSSON

MEMBER
1992 GMC
V8
2WD
AUTOMATIC
250,000 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?

1 Reply

MMPRINCE4000

MECHANIC
8,548 POSTS

Check fuel pressure with a mechanical gauge. Check spark at each cylinder and the condition of the plugs.

Check timing by shorting terminals A and B of the ALDL and start engine, set according to manufacturers instructions, usually 10 degrees BTDC.

Check fluid level in trans, and if it has been more than 2 years, change the trans filter.

If equipped with a TV cable to control trans hydraulic pressure, (a cable connected to the throttle body cam and goes to trans) make sure it is not binding or kinked.

When was your last tune up?

Do you have a check engine light? If so get codes.

Take it to any autoparts store and get the battery and charging system checked for free.

Remove vacuum line from fuel pressure regulator, looking for gas in line, if present, then the FPR has a ruptured diaphram and would need to be replaced.

Check backpressure on CAT, you would have to remove O2 sensor and rent a backpressure gauge to check it, if excessive backpressure is detected the CAT may be clogged or partially clogged.