Backfiring on a fox

[wickmaster]

Question here. I just took my BBK pipe with cats off in favor of an off road pipe. Now my question here is, why is it now backfiring? When I take it up to about 5500-6000 going through 1st and 2nd go into third and let off. Once I hit third it lets out a horrendous bang. Seems to be possibily comming out of the right bank. But my buddy was not 100% sure. With the BBK on I never had a problem.

[04 Mach1]

Check and make sure there are not any exhaust leaks. Exhuast leaks can cause backfires under hard exceleration.

[QWKSNKE]

Check and make sure there are not any exhaust leaks. Exhuast leaks can cause backfires under hard exceleration.

+1

[wickmaster]

I am about the most anal person when it comes to leaks. There are none. The only thing I can think of is the O2 sensor for the right bank was hit and got bent alittle. There are no codes though. So I kinda ruled that out. Unless the O2 sensor would not throw a code when in a rich condition. I just can't figure this one out.

[QWKSNKE]

Give us a low down on what the car has for mods

[joker]

Sounds to me like it is running rich

[wickmaster]

Give us a low down on what the car has for mods


The only mods so far on the car are Motorsport shortie headers, off road pipe and 2 1/2 in and out 40 series Flowmasters. The whole exhaust is in place, tails and all. All mandrel bent. There are no other mods on it as far as I can tell. It has K&N stickers on the air box. When I pulled the filter out to clean it, well I was in for a suprise. Unless K&N changed their filters to white paper, I would say somebody took it. HAHAHAHA The motor idles fine, surges sometimes when cold on start up but thats it. The cam sounds and feels like a stock one would. No lump or "B" cam sound. The problem did not exist with the BBK cat X pipe in place. After the change and bumping the O2 sensor I have this bang. The only other thing I was thinking was with taking off the cats I would need a K&N filter now. To help free up the intake side of things. What do you guys think?

[wickmaster]

After finally getting time I was able to pull some codes out. It would not give me any when the problem started. Work has had me busy too. Anyways, I got a 31 67 31 67 seperator code then 34 41 33 41. From what I can find in the book the 31 is something with the egr, 67 is from not being in nuetral when testing 34 is another EGR code, 41 the O2 sensor that I probally dammaged. It would not say left or right bank, and finally33 is yet another EGR code. When I put the vacuume to it it opened right up. I almost have to say the sensor is bad. The O2 sensor might be causing the backfire. What do you people think?