MAF sensor. i had this problem in my 99 es300. It would buck and i thought it was the trans. Once the MAF was replaced, it was fixed. If you know someone with a toyota/lexus that is generally around the same year, you can use theirs and can check it in minutes. the one in my es fits the wifes' 4runner.


lol, i just read that the maf is fine. Did you do an exchange or buy a new one to confirm this or check the amperage?

 

Well i will first instal the new O2 sensor and then see about replacing the MAF.

 

usually bucking is MAF related

bad a/f or o2 (the front sensor) usually just makes it run
GREAT, but either very lean (runs super awesome but will melt down eventually),
or very rich (will clog cats eventually).

 

I am noticing that while driving if I come to a red light, when I push in the clutch and let off the gas the engine runs at like 1750 to 2250 on its own before it just suddenly drops to idle.

I also noticed the the bucking is worse during rainy days and cold days. Warmer days it actually seems fine. Weird huh?

 

now that i re-read it, does some locally have a stock exhaust that they could swap so you can try?

Since you said that's when this all started i would start there.

Anytime you have issues AFTER replacing a part you go back and concentrate on that.

 

Well at first i didnt think at all that maybe it would be the exhaust because i mean what are teh chances of being the exhaust? Its a muffler,... not much going on there. I originally thought it was teh O2 sensor or sensors that failed right after the new muffler. What are the chances of a muffler killing O2 sensors? I just bought a new rear O2 sensor. If it dies then maybe,.... i dont know. Could a muffler kill atleast the rear O2 sensor?

I dont know anyone with a stock exhuast I could use. I could just remove mine and drive like so to see how it feels. I still think I will replace the MAF sensor too. Just need some lute. This truck has me currently broke.