4.0L Runs Rough when Cold

[Desert Drifter]

Hey Guys my truck has me stumped. I have a 1994 ranger 4.0L 4x4 with a manual trans. The truck runs really rough on cold start up (after sitting for 6-8 hours). It sputters lurches and hesitates at anything under 2k rpm. After about 10 minutes of driving the engine smoothes out though it occasionally will hesitate. I hooked up my code scanner and it's not throwing any codes and the check engine light never comes on.

Here's what i've checked/done:

- New Plugs and Wires
- New Cleaned Mass Air Flow Sensor
- New Fuel Filter and Air Filter
- Sprayed carb cleaner around the intake manifold to check for leaks
- Looked for vacuum leaks
- New Idle Air Control Valve
- New ECT temp switch (thought the ecu was getting an inaccurate temp reading)
- Checked fuel pressure at the fuel rail (37 psi @ key on, 30 psi Running, the acceptable range is 30 to 45 psi according to the testing kit booklet I was using)
- Performed a resistance test of the throttle position sensor with a ohm meter (operated smoothly with no spikes).


Am I missing something obvious here? I guess this could possibly be a weak fuel pump but that just doesn't seem that likely. Any thoughts?

Thanks,

Tim

 

[nb11]

Wait for it to warm up before you drive anywhere. Lol once upon a time mine had a stuttering problem similar to yours. Does it ever do a high idle? I checked for a vacuum leak and couldn't find one but the dealership did