no accel past certain point on gas

[silverclaw328]

i just put a long block 4.0 ohv into my 94 ranger and everything checks out except for one thing. i have no power past a certain point on the throttle. I'll get decent acceleration to about 1/2 to 2/3 of the way on the gas pedal, about what you'd expect for not flooring it. Then, when i hit that sweet spot, all acceleration just stops. Here's a couple things i've thought of

clutch slip - i feel like i would definitly smell it if the clutch was slipping, the clutch kit and flywheel are brand new with the engine.

Unplugged sensors or vacuum leaks - double and triple checked all connectors and vacuum lines, nothing out of place or missing

throttle cable - nothing appears to be damaged, loose or missing.

PCM relearn - i drove the truck for a good 30 to 45 minutes and nothing changed. Does it take longer to relearn PCM or did i drive it long enough?






any thoughts on what i may have over looked or if i was looking in the right area would be much appreciated

 

[alwaysFlOoReD]

Search for "throttle cable mod". Basically you attach a zip tie between the throttle pedal and the ball end of the cable. This takes cable stretch out of the equation.
Good luck,

Richard

 

[silverclaw328]

i just put the zip ties in and there was no change to the acceleration. all it did was change the loosness in the gas pedal.

 

[alwaysFlOoReD]

Next I would check for codes.
I'm not the best at diagnosis so hopefully someone with more knowledge chimes in.
Good luck,

Richard

 

[silverclaw328]

update on the symptoms. if I disconnect the battery and connect it back again, the problem gets way worse and gets better over time after driving. it never fully goes away though. PCM?

 

[RonD]

I would check the TPS(throttle position sensor) on the upper intake.

It is basically just like a light dimmer or volume control, inside is a rheostat(variable resistor) that has more resistance in one position and less resistance in another.

The PCM sends the TPS 5 volts, if throttle is closed TPS send PCM .9volts, if throttle is wide open TPS sends PCM 4.6volts, so voltage varies between .9v and 4.6v, that's how the computer knows where your foot is on the gas pedal.
So PCM bases how much fuel to feed into the intake via the injectors, by the voltage it is getting back from the TPS.
If the TPS never sends back more than 4volts then PCM never sends more fuel than is needed at that position.

TPS can be tested with volt meter, use a pin to pierce wires
Good read here:
http://www.therangerstation.com/Magazine/winter2009/throttle_position_sensor.htm

Also make sure MAF sensor is clean