O2 sensor problem

[TSImonkey]

Ok, a few of you might remember that recently i installed a 2.5" turbo back onto my car. My problem now is a check engine light which turned on about 3-4 days after the exhaust install.

I checked the code and its the Fuel Trim Code P0170. Immediately i thought the problem is my rear O2 sensor because during the exhaust install the guys Heated the sensor with a flame torch to loosen it and to unscrew it out of its socket. I figured "excessive heat + O2 sensor = bad O2 sensor" I told the mechanic to check the voltage reading on each of the sensors just to make sure that my theory is correct.

Here's my problem: the voltage for the front O2 sensor was reading 0.00 the whole time at idle, even when he revved it pretty hard, it was still reading 0.00. The rear O2 sensor however was showing 0.90-0.95v. which from my understanding is higher than normal. the mechanic told me it could be either one of the sensors. this is what he said:

it could be the front o2 sensor died and the rear one is compensating for it by reading high voltage, or the rear o2 sensor is malfunctioning because of the exposure to excessive heat during the exhaust install, and the Front o2 sensor is compensating for the high voltage by reading 0.00. I hope that makes sense

What do you guys think it is? i really need to get it fixed, my car is burning gas like never before, i used to get 19-20mpg, now i get 15-17, and i started getting bad mpg even before the exhaust install, and plus ever since the check engine light went on, my car feels really sluggish and weak. PLEASE HELP

 

[pooker]

Most likely its your rear, is your car running lean or having any other bad conditions? If it is that would lead the the front one, the rear one is mainly for emissions.

 

[TSImonkey]

well like I said, it's burning a hella lot of fuel, and it feels a lot weaker, i don't know whether its running lean or rich, but it almost feels like it can't get enough of something, i don't know what tho, air or fuel. and when i step on it , i can really smell the fuel burning and the exhaust fumes pretty good. Also, literally 5 seconds before the check engine light went on, i felt a little difference in the car driving...it almost felt like the auto tranny down shifting, but it wasn't as noticeable. i remember looking at my dash to see if anything is going on with the oil pressure and water temp. and as i'm looking at the dash the orange light turned on.

the dilemma is that the front one is reading 0.00 volt and the rear is reading higher than it should...BUT..the rear one was messed with which only leads me to believe that its that one...i don't know, i don't wanna waste money and buy both.

 

[romeen]

Replace your FRONT O2 sensor. If there was no voltage at all then it is dead and the symptoms you are describing are consistent with a bad front sensor. Problems with the rear sensor won't cause the symptoms you are describing. However, if you deleted your catalytic converter then the rear sensor will cause a CEL. There are ways to defeat this however. Let me know if you need that info.

Sparkplugs.com has good prices on the O2 sensors. Here is a link to the exact page you need, stock #234-4026.

http://www.densoproducts.com/resultsApp.asp

Edit: There may be a problem with the link I gave but just put in your vehicle info and you will find the page.

 

[TSImonkey]

I see I see, so you think its the Front one. I appreciate the feedback. I did not eliminate the cat, i went for the quiet exhaust not a can, but thanks a lot for the input. I'll get on top of this and get the front sensor. I can't stand the gas mileage and the low torque anymore. It used to be so much more torquee before the CEL went on.

Just out of curiosity, since the front O2 sensor is the major one responsible for all the symptoms i described, why do we need the rear one? besides for not throwing cel's. I know emission was mentioned earlier, what do you mean by that?

thanks a lot for the website, it worked just fine.

 

[StR8sPo0Ln]

The rear O2 sensor is not a needed part for your car. The main sensor is the front which is located on your O2 housing, is the only sensor between the two that needs to be checked. Advanced auto, has bosche sensors for around 70 bucks and they work great.

 

[DSMnewbie41]

I'm having the exact same problems he has...(CEL and smell fuel burning, feels like its not running as well). I got the high flow cat so i just assumed that the CEL was from the rear 02 sensor, but then i started getting all of those symptoms and today i think i might have been getting some knock at idle. I'm not sure because im not positive what knock sounds like. I know what the lifter tick sounds like and it was louder than that and not as consistent. Would the front 02 sensor cause me to get knock?

 

[DSMnewbie41]

I'm having the exact same problems he has...(CEL and smell fuel burning, feels like its not running as well). I got the high flow cat so i just assumed that the CEL was from the rear 02 sensor, but then i started getting all of those symptoms and today i think i might have been getting some knock at idle. I'm not sure because im not positive what knock sounds like. I know what the lifter tick sounds like and it was louder than that and not as consistent. Would the front 02 sensor cause me to get knock?

 

[TSImonkey]

that's just banging guys, great help. I went to Auto Zone a few days ago actually and i was about to get a rear O2 sensor , and it cost like 130 bucks.i was like oh hell no i aint payin for that. Turns out its not even that sensor. And that website you provided, they're so cheap i think I'll just get the front and rear and replace them both because with the rear one being exposed to so much heat with the exhaust install, I'm almost positive it'll crap out soon too.

And as for the knock you might be having DSMnewbie41, i'm pretty sure its nothing major. if you search the forum for ticking/knocking noise there's a lot of info on it. A lot of people find that using a different oil fixes the problem and that it has to do with how quickly the oil warms up when you first start the car on a cold winter morning.

Thanks a lot for all the help, greatly appreciated

Ok, I'm on the website trying to get the Denso O2 sensor, and i already ordered the Front one, but i want to get the rear one as well, but there's two types for the rear one, the description is identical but they differ in price, part # and they look different on the picture....whats the difference? which one should i get? or how do i determine which one i want???