Muffler delete equals Rich condition
 

I did some searching and I was not able to find a similar thread so here goes.

I went ahead and removed the muffler to save some weight and get some good noise. Ever since then I've been running extremely rich. I would say about 280 miles per tank of fuel (I used to average 310 to 340). So I did some research and I tried the "Idle Air Volume learning" procedure but to be honest I am sure I screwed it up:

2003-2011 Nissan 350Z - 370Z Idle Air Volume Learning Procedure | Nissanhelp.com

I can further prove this rich condition due to the fact that I had a dyno on the same day of the muffler delete and the shop tech told me I was running extremely rich.

Dyno:

http://i786.photobucket.com/albums/y...y/IMG_2544.jpg

Notice the TON of torque...I must have a v8 for like 1 whole second...LMAO!! :roflpuke2:

http://i786.photobucket.com/albums/y...y/IMG_2545.jpg

So my question is am I forced to get a tune? or is there another reset procedure I can run? Did I do the above mentioned procedure wrong? Etc?

EDIT: note that the pull showing the most power is with the filters removed.

how can a muffler delete possibly cause a rich condition? it must be something else that has caused this. allowing air to more easily flow out of your cylinders cannot cause a rich condition.

someone else chime in if im missing something here

I was confused about that one as well so let me add to the story:

When I originally picked up the car (used) I got a check engine light a few days later. Nissan (its still has factory warrantee) indicated that the car was "flashed tuned" by the previous owner. They went ahead and reflashed the ECU with the stock tune (so they say) and the check engine light went away.

I am not sure but could it be that after market tune is still hanging around causing some drama? The only thing is it was reflashed a long time ago. Why would it all of a sudden happen now after thousands of miles driven. In my opinion the exhaust is the most likely suspect. :shakes head:

Why not put back on the exhaust and check your A/F again? Since you have a '09 it could be you have (had) a Cobb AP tune. You might want to see if you can pick one up used for cheap so you can check. It would also allow you to monitor your A/F. There are other devices that allow you to monitor the stock O2 sensors, I have a Dashhawk on my '09.

Muffler delete and air intake filter delete won't cause this. Bad O2 sensor sounds more probable or some other problem causing the fuel management system to dump more fuel through the injectors than is actually required.

Right but a bad O2 censor would throw a code correct? Which in turn would trigger the CEL. Since Nissan reflashed the ECU I doubt I have a phantom flash so I am at a loss. :shakes head:

There was welding involved so I dont want any more invasive changes made. What I may end up doing is going to autozone and getting the codes checked. Either way I'll prob take it to Nissan on Friday.

Yes, in an ideal world a code would be triggered. Welcome to reality.

A bad O2 sensor doesn't throws a code. It took a long time before I figured out I had a bad sensor. Cipher helped me track it down. And yes, it ran pig rich.

I also did a Cain and muffler delete and buddy was behind me o. Freeway. When I down shifted and matted it he said it puffed out black smoke (rich) makes me wonder.... what was hour end result???

Bad gas... pulls out timing and adds fuel when it determines ping. Put some Shell or BP in the tank, then go back on the Dyno.

Please re-read the original post...I implied multiple fill ups but to be more clear...I have filled the tank more than a dozen times since then and the bad mileage is still an issue.

I had my brother (A master ASC cert mechanic) look at it and he had software to look at the O2 sensors and he noticed 3 out of the 4 exhaust sensors were reading pig rich (I.E. wide open) the moment the accelorator is pressed. I am surprised the car has not flooded. I am going to ask the dealer to reflash the ECU. :shakes head:

Another idea: what if the knock sensor is loose? Would that not cause the ECU to dump more fuel since its getting a false knock?

Sounds like bad O2 sensor dude. Just went through this with my headers. My one plug was slightly cracked so the wires werent making a complete connection on the one sensor. I was getting 10-12 city and 15-17 highway....pulled the plug and now I'm at 18 city and 28 highway. Plug for you is easy to replace anyone 2011 and up will be a bitch. They use different plugs and the dealerships can't even order them...having one specially made :/

what did you replace the muffler with?

two pipes...just the canister...the cats and resonators are untouched.

Basically two 2 ft pipes were welded in its place and my old stock tips were welded onto the new pipes.

Question/Opinion: I know how dealers can be so I want to see if you all agree with me...Should I wait to bring the car to Nissan and just put my Fast Intensions (not ordered yet) exhaust on? I have a feeling they might bitch about the welding.