HELP! P0171 check engine code

[TURBO2GO]

Uggh!!! check engine code P0171 just showed up on my NSX. I went to autozone and the code reader read it. It says:

Fuel system too lean. (cyilnder one denotes bank one)
Probable cause:

1. Large vacuum leak
2. fuel system concern
3. Ignition system concern
4. MAF sensor faulty
5. HO2S/AF sensor fault

I stopped driving the car. I am concerned about this. This car has a Comptech Supercharger. I have never had this code before. Car seems to run fine. On the dyno, last I checked all AFR's were solid and slightly to the rich side.

There is an aftermarket exahust. GT1 headers, cat bypass pipes, ARC titanium muffler. I am using the cheater 02 plugs that pull the secondary 02 sensor back a bit, but that's not the primaries.

Does anyone know what this is? It was a warm day today, I would think it should be running on the rich side. It smells rich, not lean. I have no AFR gauge.

Thanks guys.

 

[nsx200416]

my check engine light flashed 5 times last night during a spirited driving from the valley to LA but went off and has not come back on..auto zone can check the code ? i would be afraid to let them touch the car, is it involved ? I have 2004 but bone stock.

 

[TURBO2GO]

my check engine light flashed 5 times last night during a spirited driving from the valley to LA but went off and has not come back on..auto zone can check the code ? i would be afraid to let them touch the car, is it involved ? I have 2004 but bone stock.

It's just a code reader that plugs into the OBDII port. And I did that myself since they didn't know where it was. You need to have it read. You may have stored codes... but don't be hijacking my thread now! :wink:

 

[TURBO2GO]

I'm using a Uni-filter.... if that matters.

 

[docjohn]

http://www.nsxprime.com/forums/showthread.php?t=112530&highlight=code+P0171 pm larry B

 

[Ponyboy]

Could be a multitude of things. I had a lean issue on the rear bank many moons ago and it was diagnosed as a bad injector.

I'm sure Larry B will be able to nail it down.

 

[NetViper]

I had the opposite. too rich. We had adjusted the fpr so I turned it back down and cleared the code. No issue since, but too lean is worse than too rich.

 

[Liquid]

Damn, I've got to get my car fixed immediately so I can start busting your balls about this.

 

[TURBO2GO]

Well I went back to the car, started it and it's gone. CEL is no longer coming on.... weird.

 

[tof]

Smart move, not driving the car till this is sorted out. Lean burn is not a good thing in a boosted engine. But obviously you know that.

Couple of things that might be useful to Larry in diagnosing the problem...
How much boost are you running?
How many miles since you last changed your fuel filter?
Do you have a fuel pressure gauge?

I would recommend a fp gauge if you don't have one. The ones that install in the engine bay are cheap and easy to install.

Also I would never run an aftermarket turbo or supercharger without a wideband air/fuel monitoring system. It's substantially more expensive than something like a boost gauge or a fuel pressure gauge. But it's a lot cheaper than a replacement engine. But that's just me.

 

[Ponyboy]

Well I went back to the car, started it and it's gone. CEL is no longer coming on.... weird.

I wouldn't consider yourself out of the woods just yet...

 

[TURBO2GO]

How much boost are you running?
How many miles since you last changed your fuel filter?
Do you have a fuel pressure gauge?

around 7 PSI, peaking close to 8 but never reaching 8. Hovers mostly betwee 6-7.5.

Fuel filter- never. Car has 16K miles on it.

Do not have a gauge.

 

[NetViper]

around 7 PSI, peaking close to 8 but never reaching 8. Hovers mostly betwee 6-7.5.

Fuel filter- never. Car has 16K miles on it.

Do not have a gauge.

I would get the gauges for peace of mind.

 

[docjohn]

Lol I'm bringing this one up again because I had a cel on my drive home from xpo.Well I never bought my own obd-2 reader I hate having to read the tea leaves of the cicuit jump dash light fandango,so I went to harbor frieght and bought whatever scanner tool they had for 50$.Well that thing in and of itself is great ,easy to use and clears the codes.I had p0171 same as you Dave.The code has not come back after about 300 miles of driving. My nsx guru told me to put some techron fuel cleaner in the tank,which I did.So who knows if this was a unique hickup ,or is an early sign of some blockage or failing part in the fuel delivery,,,,we will see.

 

[TURBO2GO]

Mine went away, never came back...

 

[95NSX13]

I had this code also, the dealership said it could of been bad gas. Mine came on when I was driving from San Diego to San Antonio. In between there aren't the best gas stations. It detected to lean of fuel. Hope this helps out. If it comes back on, try a fuel treatment. Mine hasn't came on since. Been running 93 octane