VolVette

My '98 4Runner (V6, AT) occasionally runs very rough when in idle or when just rolling without pushing the gas. (i.e. when inching along in traffic) One day it will to it, one day it will not. A few months ago, it did this but then quit but now it's doing it again but much more frequenty. It feels as if it's going to shut off.

The only recent change is installing a new muffler (did not go with OEM, went with cheaper one from muffler shop) and that has me thinking that the O2 sensor may be giving bad information to the ECU and thus the rough running?

Also, the CEL is not on. I am going to go to auto shop and see if a reader gives me a code, despite not having a CEL on.

Appreciate any advice or experience. Thanks in advance.

Scavngr

I have a older runner but I can tell you that mine does the same thing if the O2 sensor is bad. I pulled it out and wire brushed it up just to temp fix it and it ran like a champ.
Good luck

VolVette

Thanks for the advice.

My 4Runner has 182K on it and I'm skeptical on how easily the 02 sensor would come out. Also, I understand that there are two O2 sensors? Which one did you clean?

Scavngr

Mine has 240K and it came out ok...but I have no clue how many times it has been changed before I got the 4runner. I change it around the same time as plugs. I found it makes a big difference. I only have one though. It is right at the manifold. I do not have any others by the cat.
My 88 non turbo 4runner did have two and they came out ok too though. I PBBlasted the one by the cat and let it sit for a bit then it broke free pretty well.

Good luck

cr@ves4wheelin

When I did my O2 sensor I ended up stripping the nuts on the studs. I ended up cutting it off and welding the sensor on and it worked, but I will have to get a new down pipe probably when it goes out. My truck has about 145,000 I think. Good luck man.

offset442

ya, those studs are just too small would have been better off using u bolts to secure it and welding the u bolts together to form a super clamp that can be removed with out changing the down pipe. last time i changed a head, i had the ex system apart on my truck and ended up replacing the studs and using brass nutz with anti seize compound to keep them from stripping again.

o2 sensors go bad all the time and you cant bench test if one is bad or not, unless its completely shot, as the catalyst cell slowly gets contaminated with heavy metals over time increasing the amount of hydrogen and time required to generate voltage, eventually the computer cant match the readings from the o2 sensor to the variable lookup table and you get a ruff idle or bad proformance. you can heat it up and test for voltage but you cant test the detection threshold and time thats so important for the math that the computer uses to maintain the proper running parameters.