attgig

and why does it piss off my car so much that that stupid check engine light comes on so many times?


can anyone explain what an O2 sensor does and how easy is it to replace?

__________________

DarkFury

Calling Mechmike32!!!! Calling Mechmike32!!!


O2 sensors generally monitor the emissions from your engines to detect an rich or lean condition in your exhaust (too much or not enough fuel) to alert you to a potential problem with the operation of your engine.

Here is a more detailed explaination of O2 sensors... http://auto.howstuffworks.com/question257.htm

As far as how hard it is to get to replace them... well that depends on what type of car you have, where they are located, and how many of them you have. I'll let MM34 help ya on that question.

__________________


DarkFury's Pimptopia - Don't Hate the Playa, Hate the Game!
Home of the Original OG Pimp (accept NO imitations)

modena

i had to have mine replaced on my bmw z3, cost me under $100 with parts and service

__________________
WoW - Perenolde - chars: intron, modena
Computer - AMD 64 3700+ 939 on NF4 SLi mobo (ZALMAN CNPS 9500), 2 GB DDR466 (2-3-2-5), XFX Geforce 7900GT 256mb (520mhz core, 24 pipes, 1500mhz memory), Western Digital Raptor 74GB Serial ATA HD 10k, 850GB in other HD's, 21in Widescreen LCD

Daedalus

If your car is 1995 or older you likely have 1 O2 sensor per engine bank (V-engines have 2 banks) before the catalytic converter. This sensor monitors the O2 in the exhaust for performance feedback to the ECU like DF said. If your car is 1996 or newer then you have 2 sensors per bank. The 1st sensor is the feedback sensor, same as the older cars. The 2nd sensor is placed downstream of the catalytic converter. It doesn't affect engine performance but it causes a CEL if it thinks your cat isn't working right. Check engine lights and error feedback have been mandated/standardized in the US since the 1996 MY, primarily driven by the desire to control emissions.
Depending on the code, the CEL could mean the sensor is bad (likely) or that the cat is bad. Hopefully it's just a sensor.
www.sparkplugs.com is a good source for parts. If you have a small 4-cylinder the primary sensor is probably right at the front of the engine right behind the radiator--piece of cake. If you have a new V-8 it could mean a few busted knuckles replacing it from underneath the car. If access is difficult a special sensor wrench can be bought at most auto stores.

MrGreg

I've never heard of a CEL because the O2 sensor actually detected a real problem. It's always because the sensor itself has gone bad.... so basically, it is a sensor who's only purpose is to let you know when it goes bad.

__________________
-The nerd formerly known as vectorcalculus

InfiniteNothing

Doesn't the ECU modify the combustion dynamics with the reading.

Houdini

Heh...I've pretty much come to the same conclusion, having had to replace several over the years without incident.

Daedalus

Injector duration is the key parameter that is affected by O2 feedback. The O2 sensor allows the ECU to squeeze reasonably small margins of safety on the air/fuel ratio to optimize performance and mileage. Without the feedback engines would have to run extra rich to ensure adequate safety at all times. When the sensor goes bad, cars will typically enter a conservative "limp-home" performance program.

See above regarding its purpose. Perhaps the O2 is simply less durable than the items it's measuring. That's a good thing, because they're much cheaper to replace than most other things, and don't cause any damage when they go bad. That said, they typically last 60k or more, which is pretty darn good considering the environment they live in. If a cat goes bad on a OBDII car, the MIL WILL light. If fuel pressure drops due to a bad pump and the car begins to run lean beyond the ECU's ability to correct, the ECU will light the MIL while applying safety measures. There are dozens of different codes that can be triggered based on feedback from the O2.

mechmike0034

http://www.asashop.org/autoinc/dec2002/mech.cfm

Year, make, model, engine size?

***NOTE TO ANY G|A PEOPLE WITH CAR QUESTIONS:***

I'll help anyone, any time - but I need this information in all cases!

__________________
"The price of progress is trouble." (C. F. "Boss" Kettering)
"50% of the American public has below-average intelligence. 70% of the American public now has regular access to the Internet. Do the math." (unknown)

attgig

sorry MM

2001 Jeep Grand Cherokee I6.

guiseppewv

FYI: You told him the # of cylinders not the displacement (size) of the engine. But there is only one I6 for the 2001 Jeep Grand Cherokee - a 4.0l .

Is this your vehicle?

Houdini

True, but in some older cars, the O2 sensor can go bad, or the wiring can get corroded and you either lose the engine's ability to run at all, or you get horrible mileage. It would be cool if they were placed in an easy-to-reach position on all cars, but we can always dream.

Bad gas can do it to, just as it can with your cat. If you're in Mexico, make SURE that they put unleaded gas in your car, for instance. Once you coat that platinum with lead, you no longer catalyze very well.

mechmike0034

I'd put an O2 sensor in it and see what happens if you aren't having any other symptoms.

Engine management systems from different manufacturers give different priorities/authorities to sensor inputs. This is why some vehicles that lose an O2 signal run like they always did with little effect on mileage and others will barely run.

If there aren't any other issues and the vehicle has some miles on it I'd put an O2 in it. It can be tested but few know how to properly do so and you'd burn up more time (and dollars) trying to "prove" it is bad.

Markel

A friend of mine had his O2 sensor messed up when Jiffy-Lube overfilled his engine oil.

__________________
stay low... keep moving...

rollhard

I dont really see where or how an 02 sensor can go back from added a bit too much oil.

CEL coming on because of the 02 sensor? Like what was said, it will come on because the sensor itself is bad.

If your 02 sensor is bad, your car will run like crap and your gas mileage will drop. With a bad 02, your ecu wont know or will have difficulty deciding how much fuel you need. So...to be safe, your ecu will most likely dump fuel in making you run piss rich. If your CEL comes on, check what the code is. If its a bad 02, resetting the ecu wont make it go away. IF the light goes off, it will only be a matter of time before it comes back on.

__________________
Eloy
'07 RPI 2.4GTS
Race Precision Inc.

Performance without Compromise

Houdini

Man that sucks. Not sure how that would happen, but if it did with an oil change, that really sucks. Even overfilling it shouldn't make that happen. They must have spilled oil everywhere, even into the exhaust manifold? WTF?

H <---changes his own oil and until the past couple of years, changed just about every other piece of hardware under the hood of his car. Glad those days are, temporarily, over. Once the warranty runs out though, it will be back to getting my hands dirty.