I bought my 4runner used over a year ago, excellent maintenance history. Its ran great this whole time up until a month ago when a dome light was left on and drained the battery. since then, the truck will not 'get up and go'. it starts up fine, idles fine, but when you try to give it gas it bogs down and won't go. also i occasionally hear something like a backfire coming from the front right of the vehicle. if I'm going down hill i can get it to the 3rd and 4th gear, then it can somewhat keep up. but up going uphill i almost need someone pushing.

I have already replaced the fuel filter, AND the fuel pump... these two did not make the siltiest difference.
PLEASE someone tell me they know what the heck is going on here!!

 

Good on the maintenance history......but, what diagnostics have been done related to this issue?

When was the timing belt last changed? How many miles ago?
CEL (check engine light) on?
Dirty air cleaner?
Vacuum hose leak?
Bad spark plugs or wires?
How does the oil look?
How does the coolant look?

 

Post is far too vague to be able to pinpoint the issue. Could be any number of things. Right off the bat, sounds like TPS or MAF to me.

Also, that backfire sound is the engine backfiring through the intake. You're getting lots of air and spark, but not fuel when you hit the gas. This leads me to believe TPS more than anything else, but again it could be a number of things.

 

Also, what engine?

 

Any check engine light? Easy enough to clean the air flow meter and see what happens

 

I would start out by resetting the ECU, good place to start with any electrical issues.

Simply disconnect the battery overnight and then see if things are ay better.