# Repeated O2 sensor fail, too lean code, and random misfire.



## evoL (Jul 9, 2012)

Hey guys, I have had my 06' Goat for about 8 months now and I have not been able to get rid of my check engine light. Currently I have the codes: P0056, P0060, P0171, P0174, and P0300. 56 and 60 are most likely for my O2 sensor which will make this the 3rd time I have changed it in 6 months. I have a SLP loudmouth exhaust with the cats still in place and SLP long headers. Do I need to get performance O2 sensors to go with the exhaust or is something else behind the problem? I found a vacuum hose had fallen off of the CAI which is what I believed was causing it to run lean. As for the misfire, I'm clueless. I have had that code since I bought the car. I changed the plugs and it went away for about 2 days. I have fought off 10 other codes including, running too rich, too lean, and other O2 sensor failures but the P0300 is always there. I have taken it to the dealership and they suggested getting the computer tuned but the only mods I have so far it the exhaust and headers and I didn't think it would make much of a difference or be worth the money until I added a few more mods. Any ideas?


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## svede1212 (Nov 1, 2005)

You need to have someone look at it that can log especially your AFR. The P0300 is a misfire and that could be because of fueling or something else. O2 sensors usually only go bad because of extereme age, contamination or water (condensation) is hitting it when it's hot and cracking it. I would bet your problem is elsewhere


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## 68OldGoat (Nov 23, 2009)

I have heard the dealerships have the ability to re-flash your computer to stock with their TechII if you direct them to do that.


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## jpalamar (Jul 22, 2008)

Just curious because it wasn't posted... but do you have a tune to go with your headers?


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## evoL (Jul 9, 2012)

I bought the car in an auction and had no contact with the previous owner. I have not had it tuned yet and I don't know if it was tuned before. I talked to a guy that owns a shop that specializes in LSx engines and he said that a tune probably wouldn't help my misfire problem. I also was told that having long tube headers could be the problem. The sensors are too far away and aren't getting hot enough which is causing the computer to dump fuel and making it run really rich. It makes sense because I'm averaging 9mpg. I don't know how to solve this except putting the stock exhaust back on, which I don't have. I was hoping someone on here has had a similar problem and would know how to fix this.


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## danfigg (Sep 27, 2009)

*re*

Evol you definately need a tune if your running headers. The problem here is you dont know if there is a tune in it already or if it was removed or if maybe it has a diablo tune and they did not leave you the hand held. Ask how I know this. My buddy bought an 06 auto with long tubes and full exhaust from the dealer. The stupid people at the dealership didnt even know it had headers. The car was sold with a warranty. The car had a diablo tune in it but no hand held was left with the car. The dealer tried to re-flash the computer and were unsuccessful. They had to put in a new computer. My buddy then bought a diablo sport tuner and reloaded his tune for the headers. If you keep running rich you will wipe out the rings. Check to make sure your spark plug wires are not burn and causing spark issues. You can check this at night. I had an incident not GTO related where after the car warmed up the spark plug wires would fail and there was a spark show that was visible at night. You may have to bring it back to the dealer and see if it has a tune in it or not. Unless of course you have friends who can do this for you. ----danfigg


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## SANDU002 (Oct 13, 2004)

When I added headers, they were extremely close to the #1 spark plug (drivers side closest to front bumper). I added socks to protect the wires, so if your wire(s) are burnt, that should fix the misfire problem.
Buying cars like these at auction, you never really know what problems you may encounter, and I would bet a tune plus the above should get you back to normal mpg (17-26). So understand you are going to have to spend some $$$.


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## evoL (Jul 9, 2012)

I thought a tune might help. I will definitely get one soon. Plugs and wires are good. Thanks for the help. I will update after I get the tune done.


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## Rukee (Feb 8, 2007)

Be sure to repair any exhaust leaks too as they will set O2 sensor codes.


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## svede1212 (Nov 1, 2005)

It's possible with a good tune to run the car perfectly with no O2 sensors. That's called open loop. If your tune is way off and the sensors aren't working for whatever reason you'll have problems.


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## evoL (Jul 9, 2012)

Got my tune today, more HP but worse MPG's. I don't get it. Had the rear O2 sensors turned off because apparently they were putting out little to no voltage. On the hour drive there I got 14.7 MPG's on the way back sent down to 13.1 driving the same. I'm not sure why both sensors (new) would fail at the same time or why my MPG's would get worse after a tune and turning them off. I'm stumped.


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## Solidsnk1 (Mar 27, 2013)

Maybe u need to replace the intake gasket, from what I've heard they like to leak after years go by will set codes for 02 sensors,cause the engine to misfire also


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