I have a 2011 Toyota Corolla 158k km 1.8 4cyl with a 4speed automatic. Me and my mechanic just can’t figure out the problem.
when for example idling at a red light or coming to a stop at a stop sign, the rpm often drops to 450 and then back to 700. When idling it constantly does that and the car vibrates hard every single time the rpm drops. The problem seems to be intermittent as it doesn’t do it all the time. When I shift into neutral it does it a tiny but not as bad as drive or reverse.
the coolant sensor, spark plugs, throttle body and maf sensor have all been replaced/cleaned yet the problem persists. I’ve disconnected the battery for the ecu to relearn but it often comes back after a few drives. No codes at all found with the scan tool and the data is normal except when idle drops where spark swings all over the place to keep the engine from stalling. So far the engine has never stalled on me and the ecu seems to be good at saving the engine from stalling. So for now it’s just a big annoyance as it hasn’t affected the car from starting or driving normally.
any ideas?
check for vacuum leaks
@imperator I don’t think it’s vacuum, how would a vacuum leak appear disappear reappear over and over. Additionally why would it disappear the moment I shift into neutral
vacuum leaks are a common cause of stumbling idle. They affect low idle the most. When the transmission is in gear, the engine idles higher. You asked for "any ideas" and so far you have none. so take it or leave it.
@imperator jeez relax dude all I did was ask a question.
If you disconnected the battery for a relearn then tighten up the cables even more. I know it sounds like bs but this genuinely fixed my low idle.
MAF was cleaned with MAF cleaner only right, wiped and left to dry for at least an hour?
Sparks done with care and the distributor cables checked to be snug just incase?
Did you teach it the new idle after the relearn? Revving at a steady 3000 RPM for a few minutes? A few people say 10 minutes, don't quote me on this but I think Scotty's bideo says like 3 minutes is enough. I only trust Scotty and the relearn worked for me.
I'll dig into it and let you know if I find anything useful. Scotty has low RPM and ECU relearn videos, but I'm guessing you've probably already saw em. Good luck buddy.
I was dealing with similar and thought my 700 was bad. 450 is definitely worrisome.
