Hey guys i have a sohc KA. the car used to be an auto, i swapped to a manual ecu when i did the 5 speed swap. I also installed a new fuel pump because the old one went bad.

the car has had a tune up, consisting of plugs and wires, new air filter, cap and rotor.

The car has had a stumble since i got it, it was a little one that i only experienced in closed to fully opened throttle positions(ie when shifting during full throttle). The stumble has slowly gotten worse, it stumbles much more severly and also with anything past 1/3 throttle now.

today a friend of mine suggested that i should replace the TPS, i had a spare and replaced it. as soon as i started the car the rpms climbed to 1800 and stayed there. they hold at 1800 and slightly dip in a continuous rythm.
i put the old tps back in the car and the rpms still do the same up and down. i tried adjusting it and it has no change even when its moved.

meanwhile the stumble has not changed. i pulled the ecu to look at the green light inside, and noticed that when the light is on it holds the rpm and when the light breifly goes out the rpm drops...

i think the stumble is a bad fuel injector and a dirty fuel filter, but i cant figure out the high rpm problem. please help, thank you in advance

 

you might have a vacuum leak. Mine was kinda doing the same thing. Try spraying TB cleaner fluid all over the vacuum lines. When the engine just revs up for no reason, then theres your leak

Id also get a bottle of fuel injector cleaner, replace the fuel filter to a TT 300zx one, and i would seafoam the car