Engine hesitation, wandering shifts (1 Viewer)

[imhighlander]

I'm getting used to my "new" 1998 UZJ100. JDM import with 72,000 miles. Cosmetically beautiful, and nice, supple hoses, belts, etc. I have a few little projects to address (brake flush, AHC flush) and have already been reminded how excellent this forum is.

Driving it in the Colorado foothills today I noticed a bit of hesitation in the engine, almost like it's missing a bit. I saw a post about spark plugs backing out, so I do plan to check that very soon. I'll check for cracked coil packs and anything else suspicious as well. I'm hoping to find the stumbling acceleration issue there. PO said he had replaced the fuel filter and while I haven't gone through the records to verify, I have no reason to mistrust that. Anything else I should be thinking about?

In addition to the stumbling acceleration, the transmission and/or diffs seem a little confused. My UZJ came with BFG 285s (roughly 33" tires) and I plan to keep them. When I ran 315s (basically, 35" tires) on my FZJ80 I regeared to 4:10 (IIRC) and that made a huge improvement on acceleration with larger tires. Might the 285s be just big enough to make me overgeared?

As I go through the honeymoon phase I will likely refresh the gear oil in the diffs. I'm debating changing the transmission oil & filter. I need to get the rig up on the rack and do some general looking around but I'm hoping those far more experienced with the hundo can help orient me to what I should be looking for/thinking about.

Cheers!

 

[excessive]

is it gas or diesel?

 

[imhighlander]

is it gas or diesel?

Gas

 

[2001LC]

"I noticed a bit of hesitation in the engine, almost like it's missing" If is was not for your low miles, I look first at coils. But at 72K, you should have the factory coils. Which would be, like new, unless spark plugs are walking out.

Spark plugs walking out, could do this. Tell tell signs is what sound like exhaust- tick, tick, tick. Spark walking out, is based on how many heating and cooling cycles, not miles.

"PO said he had replaced the fuel filter"
PO replacing fuel filter at such a low mileage. "May" indicate he had issue he was chasing.
When engine sit, not being run. Gas can foul.. Fuel injector needles can rust, spray patterns suffer. Fuel pressure regulators, can also be adversely affected. 2 cans of 44k in a tank of gas, may help. Onboard fuel injector service even more so. You can also, at other times, add seafoam or Chevron Techron to gas tank. All good stuff, that work a little differently. These work vert well, to clean fuel system and combustion chambers.

Make very sure radiator fins clean and that running engine coolant temp 184 to 187F range. OBDII wireless to smart phone, can log ECT, fuel trims and more. Some, like the OBDIImx, use open software. You can read ATF temp, AHC pressures and more.

Make sure all vacuum lines good. Including PCV grommet and seal in oil cap.

I'd do a full 12 qt transmission flush, with Mobil 1 full syn MV ATF. I'd not pull the transmission pan. A procedure used to check ATF for metal, if concerned. Filter what you drain from pan, the inspect filter.