hesitation/bog after shifts (automatic) Options

[krewzn_along]

I'm looking for experience to solve this problem, really an annoyance. Ideas of what it 'could' be I've got but haven't found anything to solve this yet.

Accelerating wide open or hard throttle there is a power gap, lag, hesitation, bog, just after gear shifts. It's an automatic. It's noticable at the shift to 2 and 3, where you have the power on full. It just lasts for probably less than a second and then the engine is back full power. If you accelerate at partial or moderate full throttle it does not happen.

This has been going on for a while, maybe a year - it didn't start all of a sudden. Recent maintenance includes plugs, spark wires, rotor & cap, checked the intake path and found/fixed break in hose after the air cleaner, all the hoses look/feel good, and it otherwise runs great.

Seems like maybe an ignition timing or vacuum/controls thing since it happens just after the engine's made a change in revs and manifold pressure and timing have changed/are changing. But I haven't found anything wrong.

'97 ST204 (way cool I figured that outm huh? ) at 140k mi. Timing belt's been done.
2nd Owner - well taken care of, probably driven a bit hard by my 20 yo daughter.

As for things that need attention, valve guides are probably worn as seen by smoke on start-up (wouldn't cause this problem), and I'm wondering if the valves need adjusting as the top of the engine seems noisy to me (I've had a few toyotas so I know they are often a bit noisy around the valves).

Anyone had anything like this and figured it out?

TIA,

[Bitter]

is the trans slipping or the engine is actually loosing power? when a trans slips it will FEEL like the engine is loosing power. watch the tach when it happens, if it jumps up a little then pops into the next gear then its probably going to be the trans slipping some. the condition of the fluid can give a clue as to how bad it is (if it is slipping). fluid should be nice red in color, brown or dark red is worn fluid, where as cloudy dark red or cloudy brown/black is burnt with clutch material in it.

[krewzn_along]

I really don't think the tranny is slipping because I'd expect to hear the engine revs go up like I hit neutral for an instant and I don't, anyway that was my experence with a slipping tranny years ago. I'll check the tach anyway.

The sense of bogging down is just after the shift, at the lower rpm due to the upshift.

[Bitter]

they dont always rev up hard when they slip. if its a slight slip it simply feels like a power loss, like the engine stopped making power for a second.