I have a 92 Ford Explorer 4 wheel drive with a 5 speed manual transmission. If I rev the engine in neutral everything is fine, but in any gear when I get up to about 2k RPMs the engine backs off suddenly and then after a few seconds will suddenly start accelerating again until about 2k RPM where it will happen again. I thought maybe the clutch was slipping but when this happens the engine won’t rev up when I pump the gas pedal. I replaced the Vehicle Speed Sensor and that made no difference. HELP!!!
I’ll bet your having fuel starvation problems. Check the fuel pressure. I’ll bet it is low, and drops when you give it gas. I mean press the accelerator.
A plugged or melted catalytic converter can do the same thing. I once drove a five speed Dakota with a plugged catalytic converter and it wouldn’t go over 20mph in any gear. Idled fine and all, but had no power or speed.