04 Maxima Fuel Trims

[velere54]

Hello, I recently pulled the engine and transaxle on my daughter's 04 Maxima. I replaced the timing chain guide amongst other things. I took great care in marking all of the chains. The car started up on the first try and ran great up to 6000 rpm (I didn't try higher) so the timing, vacuum, exhaust, etc., must have been ok. A couple days later troubles began. Either it's a coincidence or a wire or something else failed. I did break some wires on the harness but found and fixed them.One was the elec. supply to bank1 CVT solenoid. The other was elec. supply to bank1 O2 sensor 1. This eliminated the DTC's I was getting but it still runs poorly. Now, the car starts ok and sounds ok at idle. It will stall if I try to go above 2500 rpm. The short term fuel trims run between plus 4 and negative 7 on both banks at idle. I took it for a test drive and it wouldn't get over about 2000 rpm and both fuel trims max out at -25. I am getting no DTC codes. I've checked for vacuum and exhaust leaks, fuel pressure. Found no problems but went ahead and redid the intake plenum and exhaust systems anyway. What else would cause both banks to run too rich? Thanks, Emerson

[NutriaforBreakfast]

Just guessing here-sounds like you have done a great job diagnosing.
I hope it is just something simple. Doesn't sound related to your timing chain work.

I would make sure the alternator is putting out the correct voltage

I would check the throttle position sensor to be sure it is working

I would check the idle air control valve

You might put on a glove and make sure the EGR valve/diaphram works while the engine is hot

Honestly i don't understand the fuel trim readings but you probably understand the O2 sensors can affect how rich the engine runs
along with lots of other sensors.

[velere54]

I'm still struggling with my daughter's 04 Maxima. Hindsight is I should have listened when she said it's too much work, I'll take it to the dealer, but I really did want to learn a lot more, which I did. Anyhow, since my June post, I found that the bank 2 catalytic converter had disintegrated probably due to running too rich. I replaced it. The car started immediately and ran fine. Once again it ran fine for a day then started blasting out white/grey smoke from bank 2 only and bank 2 only is running rich. Bank 1 fuel trims are fine and no smoke. The bank 2 pre converter O2 sensor is ok. I'm about ready to take it to the dealer but I hate to start something I can't finish. I can’t find anyone who knows why one bank runs rich and the other is fine. Any ideas? Thanks, Emerson

[NutriaforBreakfast]

Sounds like O2 Bank 2 sensor is not communicating with the ECU
but the sensor itself is ok

Is there any abnornal noise in the timing chain area? Usually if something
is wrong there it is often pronounced during a cold engine startup.