austex300

hey folks, based on some engine code feedback, i have changed my mass air flow sensor, & my idle air control valve, and have also removed & cleaned the O2 sensor on the front exhaust manifold. based on the remaining code, i still have a faulty O2 sensor (bank 1, the back/firewall side manifold) & the symptom i am trying to resolve is rough idle

i had cleaned IACV last year & that work for about a year. cleaned it again this week & rough idle returned, same again after actually *replacing* IACV yesterday - so my question is: Can a faulty O2 sensor cause the same symptom, i.e.: rough idle?

vacuum all seems to be ok, just trying to chase off this intermittent rough idle based on the codes - can anyone answer my question authoritatively re: O2 sensor's ability to cause rough idle (presumedly bad info going into the computer = bad info coming out?)

thx for any help or feedback. this is a 2000 yr model two/front wheel drive RX300

carguy07

Yes.............

austex300

thx carguy; care to elaborate a scad?

carguy07

A faulty A/F sensor can make the car run poorly. Usually you will trip a CEL and the computer will kick into limp mode. Once in limp mode the computer puts everything in safe mode to try to keep the car from destroying itself. It usually runs pig rich and idles like crap. You will see your gas mileage cut in half and it will puke fuel/soot out the tail pipe.

Are you getting a CEL right now?

code58

Though you seem to have some knowledge of cars and codes, the MOST important thing you can do is post the code or codes you have had in the past when you replaced the parts you've replaced and currently also. Without those codes most help you get here will be worth just slightly more than you paid for it. You say you cleaned the front A/F ratio sensor. That is not something that ever needs to be cleaned or would benefit from cleaning.

austex300

Thx guys but really my question is not re: the mass air flow sensor; rather, it's whether the bank 1 O2 sensor, which is the one on the back exhaust manifold, can cause rough idle? I don't have the code in front of me but it is specifically this O2 sensor. So, does anyone know if a faulty O2 sensor can cause rough idle the same way a faulty idle control valve can?

carguy07

See post 4

austex300

Right, but #4 refers to "A/F sensor" which I assume means air flow sensor, as in mass air flow sensor. I assume CEL means the ck engine light indicator. Again, the ? is about the bank 1 O2 sensor, so unless we r speaking the same language in different terms...

is there any chance "A/F sensor" means "air/fuel sensor", which = O2 sensor?

carguy07

Yes, A/F Sensor = Air Fuel Sensor, Air Fuel Sensor is a fancy Oxygen Sensor (think wide band O2 sensor). CEL = Check Engine Light.

austex300

Thx for followup carguy, will likely pursue that option. Would welcome anyone else who comes across this post and would like to add their feedback based on related experience

code58

You do know that there are THREE (3) trouble codes for each Air Fuel Ratio Sensor don't you? I had the feeling from your original post that maybe you weren't quite up to speed on understanding exactly what you were dealing with in the trouble code department. I have done mechanical work all my life and have had experience with RX A/F ratio sensors, IACV's and mass air flow sensors. Not ALL of the DTC's concerning those 3 things cause rough idle.

kalali

Why don't you post the exact DTC code so you can get more accurate help? Can't be that difficult to get the codes read...

austex300

i had the codes but tossed them. mechanic had them, there were 2 remaining, both related to O2 sensor (running way rich). replaced upstream O2 sensor (bank 1 sensor 1), cleared codes & the 2 did not return. all seems well now & i think i have finally chased away these air/fuel mixture gremlins. thx to all who posted feedback

LALexusOwn

If you are still struggling with codes, sign up with www.harborfreight and you can get a coupon for an ODBC II scanner for under $100. You can also pick them up at any local parts store. Then you won't need to rely on a mechanic to clear your codes and most scanners hold codes history in case you forget. I got mine for $70 with the coupon out the door. I found that clearing codes over and over will cause the computer to keep throwing codes, then you chase down the 1 or 2 codes that keep coming up. I recently cleared codes daily for a week and the 1 code that kept coming up was O2 Bank 1. I bought the upper back O2 sensor and haven't had a CEL for 3 weeks now.