I just bought an 88 Bronco... but for the last few times I have tried to take it anywhere, it has been acting up on some of the hills. The problem fades in and out, so I am not sure whether to take it in, or just ignore it?

The problem is this: on big hills, or on long, gradual hills, when i put on any gas there is this low, rumbling sound and the whole thing starts to shake. On the steep hills I lose power (but can still make it to the top - slowly)... otherwise, I can generally maintain good speed. What is causing this? Is it serious? I'm thinking it has something to do with the fuel pump, since the rumbling stops when I take my foot off the gas.

Any advice?

Thanks!

 

Is it like an exhaust rumbling sound, or is it from the engine compartment?

 

I had the tailpipe and muffler replaced (muffler had a small hole - thought that might have been the problem..).. but to no avail. could it be something else in the exhaust system? I thought it would be a fuel problem because it only makes the noise when the gas pedal is applied...?

Thanks for replying!

 

Sounds sort of like an exhaust blockage. Hook up a vacuum guage, and check out this site:
http://www.users.bigpond.com/ergoff/vac1.htm
The exhaust restriction is on the second page.