This is driving me nuts. '98 AJ26 (NA) has intermittent hesitation problem, upon taking off and re-accelerate. When it happens, pronounced loss of power going uphill accompanies. Plugs are new, injectors supersonically cleaned, part-load breather checked, tried two MAFs with similar results, TB is new (though a remanufactured unit), fuel filter changed (but not yet the pump). No codes, but did once appeared P1230 as powertrain pending code(open power to fuel pump), so I switched the brown relays around, same condition. Tried hard reset a few times, in the beginning it seemed the car runs better, but after a couple of days it's back to having intermittent hesitation.
Now, the motor does consume oil. Every 2000 miles or so, 2.5L is lost. Mileage of the motor is about 120K miles.

Folks I need your wisdom..

 

This hesitation, does it come back strong after the power loss?
Sounds like it could be the TPS? With your consumption of oil, have you checked your EGR and tube (if you have one on that model)?

 

What're the load conditions upon take off that it happens most? Light, medium or heavy throttle? What's coming to mind is that an engine mount is separated and upon medium to heavy throttle, the engine lifts up and causes your air pipe to come unsealed or it has a slight rip in it. Once you idle the engine then it reseals itself. Just an idea.

 

to Addicted to boost:

This is the wildest diagnosis I've heard! But you might be hitting something!! Because lately the car has also been making slight ticking noise going downhill and in turns! I have been suspecting something is on the way out in the front suspension! The hesitation happens mostly during medium to heavy throttle!

 

Just a thought, did you reset the throttle cable adjustment when reinstalling the new TB?
How old is the fuel filter?

ps I like Boost's thoughts on the matter, you can check one side engine mounts by driving the car on the brakes, pop the hood, put it in drive, have someone stand on the brake and blip the throttle while you look for engine movement up^.