Hi Folks, I've read the FAQs and searched on this topic. I just want confirmation that I've come to the right conclusions.

My battery recently died on my 2k Maxima, after which I started to get strange problems when the engine is cold, a few moments after putting it into drive. I also remember noticing an occasional knock sound while clearing snow off the car this winter. I heard it again today while checking for codes and checking out the O2 sensors and MAF sensor output via ODB-2.

The problems I experienced were sudden stuttering possibly followed by stalling, eased by taking my foot off the gas and reapplying it. This gradually got better over a period of a few days after the battery replacement. I then happened to hit the highway a few days after that and had a serious lack of power at 3000-4000 rpm and a delayed shift. This is less pronounced now too, but is still somewhat of a problem.

Today I decided to hook up my PDA tot he ODB-2 and found that the bank 2 O2 sensor was mostly sitting at .250-.260V without variation. I've read the FAQ on the O2 sensors... Shouldn't this have some variation above .260V? It spiked twice to >1V so I suspect that was bad data, otherwise it never varied. I thus hypothesize this O2 sensor is bad or faulty.

The second hypothesis is that the MAF is bad as well. I've suspected this for some time, but I've never had syptoms that point clearly at a bad MAF until just now -- power issues at highway speeds / 3500+ RPM. I will have to order my MAF from Dave or someone else in the US. I think they still charge too much for them here ($600 CAD).

I believe the car has its original MAF and O2 sensors.

Would either of the two above problems cause the single klunk type knock sound that I hear once in a while while the car is idling when i'm clearing the snow off it?

PS - I have new coils and plugs 50000 km ago.

Thanks in advance.

 

Unless you are getting a code that the o2 sensors are bad I would change the MAF first and see if it helps. Also, the rear o2 sensors have no influence on how the car performs (only the front O2 sensors give information that is used by the ECU to adjust performance)

My bet, the MAF