getting to the bottom of this...

[bassplayaz06]

so i got the car diagnosed, and i have 3 codes shown.P0136 - saying the 2nd sensor is taking incorrect readingsP0171 - sensors are thinking the fuel/air mixture is too lean, keeping the fuel trim valve open constantly trying to make it even, but actually making it richP0420 - catalytic inefficiency, caused by the second sensor getting incorrect readings compared to the first sensor.any ideas which part is bad? or what to do?I have the diagnosis charts and how a shop would go about checking the parts, just asking input here.

[bassplayaz06]

now that i'm looking over the papers, it looks as if i have a vacuum leak somewhere.

[lovemyraffe]

If you have a vacuum leak, check the intake manifold gasket.

[A Psycho Martyr]

supposedly you can check iy by letting the car idle and spraying throttle body cleaner around where the sel is. If the motor sucks it in and reacts to it, you've found your leakWatched my uncle do it to mine. You may wanna get a second opinion tho, as I'm not a mechanic and I have a horrible memory

[bassplayaz06]

well i tried what psycho said, and there's a leak somewhere. i ordered a manifold gasket kit from o'reilly auto for $17 on school discount. doing the install whenever i get a chance. probably friday after school. if that don't do it, then it's the O2 sensor.

[bassplayaz06]

so i've got a bad O2 sensor and a leaking intake manifold gasket.

[lovemyraffe]

Quote, originally posted by bassplayaz06 »so i've got a bad O2 sensor and a leaking intake manifold gasket.Sounds like lots of fun

[bassplayaz06]

yeah, especially when an O2 sensor is $80.

[htrdce69]

I had the same P0420 code a few months ago. I changed the O2 sensors and still had the same code which lead to a bad cat. Apparently, the only cat that will work on the GT is the OEM stock item...$700.00 and a week later, I finally get my car back and haven't had a code since. Wish I had found this forum earlier so I could have read about experiences that others have had with this.

[northvibe]

check Rockauto's website, they have WAY better pricing on parts like o2 sensors I've found. THey had plug in play oem ones for cheaper than the generic bosch ones at napa/etc.

[northvibe]

Quote, originally posted by htrdce69 »I had the same P0420 code a few months ago. I changed the O2 sensors and still had the same code which lead to a bad cat. Apparently, the only cat that will work on the GT is the OEM stock item...$700.00 and a week later, I finally get my car back and haven't had a code since. Wish I had found this forum earlier so I could have read about experiences that others have had with this.Ya that 3rd cel the OP had, looks like a bad cat, but the rear o2 is usually after 1 or 2 cats so if theres a issue up front of the engine at the other o2 that could cause it as well. Once the front o2 sensor and IM leak is fixed and if it is still throwing rear o2 issues or cat cel's then I would look at a cat issue. You could remove that cat but then you run into emissions issues if you live in a state that tests that. I think a aftermarket cat can work on a GT, specially aftermarket downpipes and such. but welding a new one in is probably a pita.

[wallyuwl]

Looks like an intake manifold gasket and bad 02 sensor. I just replaced my gasket and put in a new pre-cat O2 sensor (and some other things, but irrelevant to this). Check Amazon for the Denso O2 sensor. I think it was like $63 or something for me.

[bassplayaz06]

well i replaced the O2 sensor and that fixed it all. still waiting for the gaskets to come in though.

[coldfusion11]

Will spraying TB cleaner around the intake manifold gasket create the engine to surge, locating the leak?

[bassplayaz06]

yeah, something like that.