Weird Throttle/Load issue confusing my mechanic

[brachypelma]

Hey all,
Having some weird stuff happening to my '02 4x4 and was looking for your expert input! My friendly mechanic is confused too. Let me know your thoughts.

Problem: After 'warming up' (~30 sec after starting), At any throttle position (and idle), the engine rpms pulse at ~1sec frequency, up/down 3-400 rpms. MPG is down from ~20 to ~15.

at idle, checking the odb2 data, the ecu is reading 'load' fluctuate from 10-20% (which I assume is why it's blipping revs up).

Things I've tried, with no change:
- Intake smoke test (no intake leaks)
- Cleaning MAF
- new spark plugs/wires
- replaced AF/O2 sensors
- new PCV and gasket
- cleaning throttle body
- swapping out throttle body for a different (used) unit
- running it with power steering belt removed

Any recommendations?
Thank you guys!

 

[19963.4lsr5]

How old is your front O2 sensor?



Sent from my iPhone using Tapatalk

 

[brachypelma]

Sorry, forgot to mention; I've replaced both the A/F sensor and the O2 sensor, and to answer, about a week old.

How old is your front O2 sensor?

 

[JRZEE2000TR4LTD]

I'll throw this out there. With the AC on it will do what your describing if your refrigerant is low. Probably not that though.

Sounds kinda like timing. Crank sensor? Cam Sensor. Is the harmonic balancer/lower TB pulley secure?

 

[LittleCaesar]

Are all the replacement parts OEM, or at least Denso?

Throttle position or % amount during these times? ECT values?

 

[brachypelma]

Yeah, it happens with AC on or off...
I'll check timing, but in theory if it were timing, it'd be happening all the time; before warm-up too.

I'll throw this out there. With the AC on it will do what your describing if your refrigerant is low. Probably not that though.

Sounds kinda like timing. Crank sensor? Cam Sensor. Is the harmonic balancer/lower TB pulley secure?

 

[JRZEE2000TR4LTD]

Yeah, it happens with AC on or off...
I'll check timing, but in theory if it were timing, it'd be happening all the time; before warm-up too.

I agree. So it sounds like it is probably going into closed loop and acting like it is. OR Possibly a component acting up when it gets hot. A good OBD2 scanner should help pinpoint the problem.

Caesars suggestions are good places to start.

 

[gamefreakgc]

I was going to say IAC or problem with the TPS sensor, but if you swapped the throttle body it would have shown improvement.

I would double-check your wiring to the TPS as well as the MAF to make sure there's no damage. Also double-check your ground wires and your battery terminals, bad grounds cause all sorts of weird gremlins.

 

[spartacus]

in addition to what everyone else has recomended above the camshaft position sensor not functioning properly would have these symptoms too.