2001 Lexus ES 300 (3.0L, automatic)
The check engine light is on and I scanned it: cylinders 1, 3, and 5 (bank 1) are misfiring. I’m basically getting these 3 symptoms when driving:
1) Cylinders appear to randomly misfire (whether under load or not)
2) Sometimes (apparently randomly) when I brake, the brake pedal doesn’t go all the way down, and I have to press down quite hard to brake properly. It’s almost as if the brake fluid is low, except the pedal doesn’t feel spongey but it feels hard and I can barely press it down. This only happens occasionally, most of the time the brakes are fine.
3) Almost always when driving on the highway it feels like my car would downshift for a second, and then shift back up to the normal gear. Another way to describe it would be like the brakes are pressed down part way for a bit (car suddenly slows) and then released and the car returns to normal. Or another way, as if the car suddenly started driving through honey, and it slowed down a bit, and then returned quickly to normal paved road. It’s kind of hard to describe but I hope you get it.
So far I’ve:
1) Replaced 1 damaged vacuum line (all others looked good)
2) Cleaned the MAF/ IAC valve/ throttle body
3) Replaced all 6 spark plugs
4) It looks like it has a fairly new oil filter (presumably from a repair when I brought it into the shop for something last year)
The symptoms are still present, what could the problem be?