rough running @ low RPMs

[Karu89]

i have a 2001 3.0l non flex 5 speed with 222k miles and runs choppy from around 1000-1500 rpm during take off in 1st to sometimes in 4th gear. the choppiness is like it's not getting enough fuel.

i'ev already replaced the fuel filter and the MAF is clean. any ideas what the problem could be.

 

[planeflyer21]

Did you clean the sensor at the other end of the intake tube, opposite the MAF?

I had a similar rough running and cleaned the MAF and other sensor/valve at the same time, with the MAF-safe cleaner.

 

[RonD]

After engine is warmed up and idling, unplug the 2 wire connector on IAC(idle air control) valve, engine RPMs should drop to 500 or engine may even stall, either is good it means no vacuum leaks.

If RPMs stay at or above 700 then you do have a vacuum leak


Low fuel pressure shows up first at high demand, i.e. climbing hills or driving above 60MPH, engine "runs out of gas"
Mid or lower RPM issues shouldn't be fuel related.

Throttle position sensor(TPS) is a moving part, like a volume control or light dimmer.
When foot is off the gas pedal TPS sends computer under 1volt, .69v to .99v is specified.
As you push down on the gas pedal TPS sends more voltage back to computer, like turning up the volume, with foot "to the floor" TPS sends computer above 4.5volts.
IF(big if) you have a "bad" spot in the TPS computer could "think" you have taken your foot of the gas pedal, i.e. instead of computer getting 2.5volts it drops to 1.5volts so computer lowers fuel amount.
Long shot
But keep track of your "foot position" on the gas pedal to see if roughness happens at a certain "foot position".

Early 2000's Ranger 3.0ls did have coil pack issues, there was a TSB about it, they need to be replaced.

 

[Karu89]

After engine is warmed up and idling, unplug the 2 wire connector on IAC(idle air control) valve, engine RPMs should drop to 500 or engine may even stall, either is good it means no vacuum leaks.

If RPMs stay at or above 700 then you do have a vacuum leak.

it drops to i'd say a little over 500-600 rpms but it just throw the engine light up and saddly i don't have an OBII scanner/reader yet so i'll be heading to autozone down the street to get it checked out and cleared but it's now not doing it as mush but is starting to happen at higher rpms and rarely when i put the peddle down more for hill take offs or climbing but not as bad at the the lower rpms

the cose was for the IAC and spent sometime tracking an AZ that could still reset codes

 

[Karu89]

ordered an OBII should be here on monday then maybe i can get to the bottom of this but it has tried to stall on me at a red light and now seems to be running smoother as if if coughed up a hairball

 

[Karu89]

ok ron your right on the money with the IAC/vac.leak so now i guess i should go hunting for the leaks. i pulled up the rpm tac and the rpms dropped from 845-920 or so and only dropped down to 741-753

 

[Karu89]

checked all the lines that i could see and no leak...also i did a seafoam on the truck lastnight and today its been alot better just everyonce in awhile it'll cut out like it was only when i'm going up a hill or if i try really hard to get it to mess up