I got my car tuned back in socal right after I installed all the bolt ons then moved to AZ. After I moved here last summer the CEL have came on twice and I've got it tuned twice but today it came back on again... I replaced the o2 sensors and checked for exhaust leaks last time when I had it tuned. So far I got intake, plenum spacer, headers, art pipe and cat back and it's a 04 touring with almost 70k miles. Right now I can only think of the o2 sensor on the headers or the fuel pump? Anyone know any other possible causes? Thanks in advance.

 

what codes

 

Oops.... P1273 and 1283

 

exhaust or vacuum leak. Possibly bad cat(s) as well. Smoke test intake and exhaust, report back.

 

will do! I'll get a smoke test done and report back. Also I don't have cats, I got ART pipes and I don't think ART pipes throws CEL?? At least that's what everyone says...

 

Art pipes use o2 extenders which can cause bank lean codes, at least on certain model/years. What's happening is the o2's are reading lean due to the extenders, the ECU adds fuel to compensate, but still sees lean readings on the o2's... CEL time. so you're actually running extra rich and getting **** mpg's, but the ECU thinks you're lean. That said the art pipes are probably the cause, assuming everything else is straight.

 

Ok thanks a lot. I'll get a smoke test done tomorrow and see how it goes. My car does get pretty bad mileage, I think 19 mpg and mostly highway too.....

 

Assuming there are no leaks, you're going to have to live with this or get some test pipes without o2 extenders. O2 simulators might help with the art pipes though, but I don't have any evidence or experience with that.

 

i thought the sole purpose of the rear o2 sensors was to just make sure the cat convs were functioning correctly and that the front o2s were the ones that communicate with the ecu to determine the correct a/f ratio. i thought the rear o2s had nothing to do with a/f. am i wrong?

 

^I'm pretty sure both are used for that. In for the answer though

 

Both are used.

 

ah damn, so if you delete the rears in the tune so the text pipes dont throw cat codes, will that screw up how the engine runs after a tune?

 

Place the rears directly in the exhaust stream, then you can delete the P04x0 codes so you don't get a CEL and the ECU will still use the sensors and engine will run properly and won't throw the lean codes. There's no way to delete the sensors completely...

 

will you get the proper readiness lights when clearing the 4x0 codes?

 

Have not tested this yet. I can usually avoid P04x0 long enough to get thru, I'll try with them deleted next time.

 

ok, but my test pipes have an extension where those o2s go, does that extension mess up their readings?

 

ya just turn them off and see if you get ready status after a couple drives.... i need to get a cipher, so i can play with my reflashed tune.

 

Edit: sorry for off topic op, i will start my own thread.

 

What is a smoke test and how is it done?
Did you find any leaks?

I also have ART pipes and I am also getting P1273. I also get poor mpg (~16 miles).
This is a 2004.5 G35cMT (AC406) with 90K miles.
I was hoping that professional tuner would be able to dial this out with Fuel Compensation table, but he didnt even want to touch this table.

If ARTs extenders are to blame, is my only remedy to weld a new O2 bungs (as Andrei did )?

Thanks

 

Unless you can see you're getting a rich fuel condition, it's not that. But it's worth checking if possible.

You can test by clearing the ECU and unplugging the rear sensors, you'll get a code, but your MPG should return.