Odd Problem...300 inline 6

[rusty ol ranger]

My buddy has a 93 F150 2wd with a 300 6 and a 5sp....

I am stumped on this one....

It starts, and runs fine at idle, give it gas and it misses like mad untill about 2000, is smooth from 2000 till about 3000, and from 3000-3500 misses liike mad.

Its very pronounced and very rythmatic, always the same RPM. However, sometimes it will alternate, and run smooth at idle-2000, 2000-3000, and run like shit at 3000-3500.

Or sometimes it will run like shit idle-2000, smooth 2000-3000, and 3000-3500.

Above 3500RPM the engine is really rapping, but sounds like its smooth.

I am absoultly stumped. Its good fuel pressure and when it runs smooth has plenty of power....

The check engine light is off...

later,
Dustin

[timster]

check your distributor, the stator and the ignition control mod. also check your o2 sensors, I would check that your fuel pressure regulator, cap rotor, vac leaks, EGR, map sensor thats where I would start. Just start checking out all the systems, the 300 is a damn good motor, it should a very long time.

[rusty ol ranger]

I know the 300 is an awesome motor....best one ever built IMO.

Would a TPS throw a Check engine?

later,
Dustin

[Ranger44]

My friend has the exact same truck. lol

The TPS is more of a driver imput sensor. It will usually only make an engine stumble when you stomp the pedal, etc.

Hmmm. My thought would be that it was ignition related.

But check the FPR. Just pull the vacuum line of the top and see if gas come out. My nissan did this and ran kinda simular.

O2's would usually make an engine miss, but i wouldn't think that bad.

Another thought that comes to mind is unmetereds air getting into the engine. Any intake leaks? I guess a good old carb cleaner check would work.