Hi, I own a 2000 maxima with 86,000 miles on it.
Recently my SES light turned on, I went and got the code read at Autozone.
It came up as a P0171 (Bank 1 running lean).
I then took my car to a local mechanic who told me that it was probably my fuel filter being clogged, dirty fuel injectors or perhaps the cheaper brand gas that I was using (Costco). Since then I have cleaned my injectors, got my fuel pressure checked to eliminate the fuel filter as being clogged and I have been using Chevron Premium gas. I also han my exhaust checked for leaks(I was told by a different source that may have been a factor as well). None of these things so far have kept the light from coming back. Could this possibly be my ignition coils (I believe they are original)? I have an HKS ignition system, Injen intake, stillen y-pipe if that is of any relevance. Any help in this matter would be greatly appreciated.

 

It's usually one of two things. Either you have an intake leak or your MAF is about to go. You can purchase a MAF sensor from DaveB for around $85 and replace it yourself.

 

What kind of gas had you been using before? Unless you were running pure schlock through it, I doubt it could have clogged the fuel filter to that extent to detonate. Here are the possible causes from the 2000 service manual, in order:

- Intake Air Leaks
- Front heated O2 sensor
- Injectors (def / dirty)
- Exhaust Gas Leaks
- Incorrect Fuel Pressure
- Lack of Fuel
- Mass aif flow sensor

Your coils are out of the loop on this bug... I'm thinking most likely Front O2 sensor. You may want to do a search on here, I've seen some threads where folks have had them replaced (and then they do the rear as well at the same time...)

Good luck!!!

 

I've been using Costco gas which is a "buy in bulk" place like Sam's club or something. I didn't think it was the gas eiher. The first thing I did when I got the code was to change out my 2 front o2 sensors. (the best prices are at http://www.oxygensensors.com/ by the way) Is it possible for bad ignition coils to harm your engine before it trips a code, or starts pinging? Thanks alot for the help guys, I really appreciate it!

 

Ummmm... not really...

In theory, the engine *could* be harmed by the pinging itself (detonation), but engines are only really hurt under boost (turbo / SC)... NA engines typically just exhibit loss of power and a little added wear from the stress of the pre-detonation. A bad coil will not "travel back through the circuit" and hurt anything else.

This one really is tricky, I've read through the whole diagnostic in the book and I can't think of too much else (and I'm an engineer!) Have you replaced the Mass Air Flow sensor? Book calls it out, and it's possible it could cause this problem, but I think you'd see other symptoms first.

Let me know what you find...