My 90 4x4 Toyota pickup had a loose wire hanging down and the wires were rubbing together and causing the EFI fuse to blow. Well i didnt have time to rewire since i was running late for work so i just cut the 02 wire in half, taped them up and separated them from each other. Well i did throw a code , knew that would happen, but now my truck runs noticably smoother. What should that tell me? Do you think i need new 02 sensors or new cats? Besides the light it wont hurt anything to run it like that will it? gas mileage hasnt changed as far as i can tell.Thanks for any replies

 

it was the rear driver side sensor if it makes any difference

 

i'm pretty sure your o2 sensor was probably bad. i'll bet your mpgs go down without it working at all now. someone will surely chime in with more info for you.

 

I thought there was only one o2 sensor on that model (I may be wrong, but I've only seen one under mine and it it located in front of the cat). I would change the sensor for sure. Listen for rattling noise in the cat, and notice if it gets excessively hot at or in front of the converter. I would change the sensor first, notice the results, then look for trouble with the converter.

 

on the way to work today it seems to get slightly worse mpg than usual. like i said its way smoother and no real power increase that i can tell but gas mileage SEEMS to be lower. i havent checked to see how many sensors are under there but i guess ill go ahead and order one (or two) and rewire it back like it was. i would like to say this board is the most helpful board ive seen anywhere and if you ever need suspension stuff PM me. thanks guys

 

without the o2 sensor, the engine goes into safe mode and runs excessively rich. this will cause your milage to go down, probably lose some power, and you may destroy the cat because you're putting all the hydrocarbons and CO in but no NOx to take them back out. the way the o2 sensor works is that it gives about a 1Hz oscillation to have the engine run slightly rich and then sligtly lean and then slightly rich and so on. that way on average the engine is running at the right mixture. when the engine is running rich, it pours lots of CO on the catalytic converter, then when it runs lean is pours lots of NOx on the converter. the NOx+CO turn into CO2 and N2 which are much more harmless than NOx and CO. so for the cat to work right you need the oscillation provided by the O2 sensor.

 

 

only thing i dont understand is if my 02 sensor was bad, wouldnt it have run WORSE before i cut the wires? it gets a few gallons less on mileage now but i swear it runs smoother and maybe has a tad more power? i just hate to buy a $50-100 sensor if i dont have to. my CES light is on now so i know it works so wouldnt that tell me that my 02 sensor is good? might be a stupid reasoning but am i thinking the right way? thanks again

 

Not necessarily... It's probably running "better" and with "more power" now 'cause you were running lean to start with.


Nope, the ECU won't toss a code until the O2 sensor goes out of spec (shows less than 0.2v or more than 1.2). As long as it stays in those bounds, then the ECU is happy. It doesn't try to figure out accurate it may (not) be.

 

ok ill pick up a new sensor this weekend ,hook it all back up to see how she does. big thanks for the replies

 

o2 sensors are only like $25 at www.sparkplugs.com

 

I paid about $65 for mine.

 

ya i dont know what kid of 02 sensor that is but everyone ive ever bought was like $80 (the one for my bmw i bought 2 months ago was $95)

 

Don't get an aftermarket one, go oem. I have heard bad things about aftermarket O2 sensors