Engine idle problem.

Did you check the fuel pressure? Possible restriction in exhaust system.

new spark plugs this decade. (a tune up?0
the filter is part of all 60k tuneups. letting it clog wrecks good pumps.
my wild guess, its lack of fuel flow, do to old filter.
or low fuel pressure.
car is identical to a Corolla. so is not unique or rare as some Geo cars are.
the cam belt not changes, invites valve kissing piston tops. BOOM
end of engine. (costs more to fix then worth of car)
the word is bogging, my engine bogs
if if bogs WOT (wide open throttle) and dont catch up < ITS NOT THE TPS. ever.
tps bad causes short bogs, called hesitations.
The map sensor , is what measure air flow and the ECU matches fuel to this air flow.
my guess, is it does that, but fuel pressure is like 15PSI, bad.

does thr engine rev upwhen started than idels back down.try idel control switch and map sensor

Sounds like a fuel pressure issue. Have you changed your fuel filter lately ?

look for a serious exhaust or intake leak. look for bad wires to the o2 sensor or map sensor. just for starters.

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your fuel filter might be old and clogged. try replacing it. if it is and not enough fuel can get through, the engine will stall when you let more air in (step on the gas pedal).

check on the rear of the engine below the throttlebody area there is a vacuum line that collapses or splits and cause this

i think the dist is adjable try advanceing it some times the after market caps are a little diffront

could be a fuel problem have u checked the fuel filter

ecu is bad did you try to jump start the car or had any dead battery lately?