low rpm engine hesitation

[Fergifruitchew]

recently at low rpms while driving (manual) my cars engine hesitates, kinda sputters, at high rpms is runs perfect. what could this be? i was thinking either fuel filter which is inside the tank, or a sensor on the intake could have dirt or oil on it.

[fishexpo101]

There is an intake air temperature sensor on the intake. But sounds more like a fuel issue. Could be a dirty filter or faulty pressure regulator - but generally should cause problems at higher RPMs too. I believe you had the earlier 8th gen Corolla (non-VVTi)? Could be the injectors are fouled - not able to spray evenly at low engine speeds causing some stumbling, would also tend to run OK at higher RPMs.

Vacuum leak(s) could be another possibility - misadjusted TPS sensor on the throttle body or a throttle body in need of a good cleaning are other possibilities.

[Fergifruitchew]

yea my engine is a non vvti, i have a complete spare intake throttle body, complete fuel rail too. i should check my filter.

[fishexpo101]

Does it stumble if you are running the A/C or defrost? If it does not, could be a clogged idle-air control valve on the throttle body - those can get pretty gunked up, especially if you got some miles on the car.

Could always toss on the spare TB, assuming that everything works on it, and see if it makes any difference. If it does, then you know the culprit is something on the throttle body (gum, varnish, bad vacuum hose, etc.).

[Fergifruitchew]

hm, the ac is always off i never use it, but my knob is pointed at the windshield and feet, maybe defrost?

[Fergifruitchew]

i found out what it was, the spark plugs were frigged up, i dont know why i never checked them before but whatever lol