98 tacoma back fires

98 tacoma 4cyl. engine runs good under no load, very smooth at any rpm. Under load (in gear) it hesitates and backfires during increase demand at any speed. It will smooth out but start to hesitate and backfire when you step down on it.
ignition modual?

Sounds like you have a misfire, not a back fire. Check the ignition timing, battery connections, plugs, wires, distributer (if you have one), etc. Basically give the ignition and electrical a good look over.

Got it fixed, thanks. It was a plug wire shorting to ground at the plug. Runs great now.

Thanks for letting us know you found the problem.

Clifton