Hi there, i have a 94 ranger with a 4.0 ohv and when i accelerate i have to drive it like a carburated engine. at wide open throttle the engine will not accelerate, just kind of stumble over itself but does not drop rpms, once i back off to 75% it will surge ahead no problem. this happens at all speeds in all gears, ive replaced plugs and wires and will be cleaning the maf and checking the coil pack tomorrow. any other ideas as to what i should check? possibly one cat is plugged?

 

If you have a vacuum gauge, $25, you could check if exhaust system may be getting plugged up, as air flow increases thru the engine a partially clogged exhaust will cause a build up of back pressure so all the new air:fuel mix can not enter a cylinder, causes loss of power until air flow is reduced to a level the exhaust system can pass.
Ol' potato up the exhaust pipe trick, lol.

TPS(throttle position sensor) tells the computer where the throttle plate is so where your foot is on the gas pedal.
Computer sends it 5volts on the top wire, inside TPS is a variable resistor, like a light dimmer.
Middle wire sends back .9volts when throttle is closed and 4.8volts when throttle is wide open, and of course the variable voltage in between.
I assume you have a volt/ohm meter if you are checking the coil pack.
Set it for DC volts, 20vDC if available
Use a sewing pin to pierce the center wire on the TPS
Turn key on
Ground the meter on the engine and test Pins voltage, .7-.9v is expected with throttle closed.
Slowly open throttle manually while watching the voltage, it should steadily climb until it gets above 4.6volts at wide open throttle, 4.6-4.9volts is expected
If volts stops climbing or you see voltage jumping around, replace TPS.

 

Pulled the maf and it had some dirt on the downstream wires, cleaned it off with vinegar and its all running nicely now

 

Good work.

Thanks for the update

 

Also just bought myself a '94 4.0, has a similar issue. She idles just fine but has a random miss/stutter anytime I'm accelerating. I've replaced the TPS, ICM, and MAF, along with new plugs and wires, to no avail. I'm going to do a fuel pressure check tomorrow along with the coil pack but just wanted to check with you guys, see if there's anything I'm missing.

Cheers and thanks!

 

Didn't know that you could clean the MAF with vinegar. That's what i like about this forum, learn something new every day.