Hey guys, I have a 04 maxima automatic trans. Trying to get it to pass emissions. I keep getting a p0300 code. Took it to the dealer they told me I needed all new coils and plugs. Somebody put aftermarket coils on it previously. So I put oem coils and plugs in. No change. Went to alldata and started doing diagnostic checks... Checked the fuel injector resistence, changed egr valve oem, changed maf oem, borrowed a buddys smoke machine no vaccume leaks found. So I took it back to the dealer and they said it needed two bank 1 af sensors, and only put. Sensor 1 in due to the fact I needed a new cat installed. So I baught two converters from advance and put them on cleaned the flex pipes really good and put 3 other ntk sensors in. I still have the same problem. I looked at various sites tried to do a ecu reset, idle volume relearn with the gas pedal.. I did get codes p1281 and p1283 before but since I changed the sensors they haven't come back. The idle bumps up and down from 638 to 700 when it does I noticed the car changes from closed loop to open loop. The short term fuel trim for bank 1 is -25 and the short term fuel trim for bank 2 is 25. And long term fuel trim for bank 1 is -1.6 and long term trim for bank 2 is -3.4. Is there any other ideas or thoughts about this? I'm afraid to take it back to the dealer, the first time was a waste.

 

You've changed out some stuff. So, if the old stuff is what possibly gummed her up, then I am thinking you gotta un-gumm her. I would seafoam her and take her for a long highway drive. Maybe that will clean out the pipes a bit, so to speak, and get you your pass on the emissions test.

 

Check your grounds, make sure they're clean. Had something similar after engine swap in my 04. Bad grounds were to blame.

 

Yup, L36, is pointing you in the right direction Make sure them grounds are clean and tight. This is, unfortunate, a process of elimination, as you have witnessed by how the dealership is treating you, until ya find your particular issue.