4.0 RPMs choking

[1994fordranger]

so while driving down the road it randomly began, the rpms would drop by a few hundred for a split second, and it felt almost as if i was tapping the brakes, so i went home, by the time i got there ( 15 minute drive) the rpms were constantly dropping by around 500, i would have to keep it above 3000 rpms just to stop it from stalling on me, it wouldnt even idle because of it, anyone know what could cause this?

 

[Lil-Pony]

tps? but that doesn't explain the wanting to stall.

 

[trader007]

probably the same reason mine and thousands of other rangers do it. the very reason nobody can figure out

 

[Lil-Pony]

probably the same reason mine and thousands of other rangers do it. the very reason nobody can figure out

hahaha +1^^^^^

 

[adsm08]

probably the same reason mine and thousands of other rangers do it. the very reason nobody can figure out

I bet if you left one that does it alone with me for a week I could figure it out.

Postin' from teh Galaxy

 

[RonD]

TPS ...maybe.

Throttle Position Sensor(TPS) tells the computer(PCM) where your foot is on the gas pedal.
It is located on the upper intake connected to the throttle plate.
It works the same as a light dimmer or volume control, the PCM sends it 5volts, and the TPS sends back 1 to 5 volts depending on where the throttle plate is,
1 volt closed
5 volts wide open throttle

You can test a TPS with a OHM Meter or Volt Meter, just manually open and close it while testing its signal.

The TPS can get "dead spots" so if you hit a dead spot while driving the voltage can drop to 0volts so PCM thinks throttle is closed and idles the engine, RPM drops, until you move your foot up or down on the gas pedal, getting TPS off the dead spot.
But engine shouldn't stall even if TPS sends back 0volts.

You could have a fuel pump relay issue or fuel pump issue, even fuel filter.
Fuel filter is $10 and easy to replace.

Does engine start and idle now?

 

[trader007]

Turns out, for me, the upper intake gaskets are leaking. I think my whole plastic intake is warped...

Ive seen gaskets that are thicker, much thicker then the OEM ones. The ones I put in a year ago were OEM thin style, and you can hear it hissing until the motor warms up.

Instead of buying a new gasket set again, I just RTV'd the crap out of it. I probably will never be able to pull off the manifold again, but hopefully this works for awhile.