P0171, CEL light but car is running ok (1996 NSX-T, 100K miles)

[Ron1999]

Got the car two weeks ago, drove it almost 10 hours from its location to my home,
It wasn't idling well from the get go, but the car drove and i made the drive (including 2 fuels stops and multiple other stops) pretty easily.

This week, after not driving it for a couple of days i took it for a spin - CEL light comes on
I run a scan - got P0171 error, lean fuel on bank 1
Changed spark plugs - problem remains

I ordered O2 sensor.
Question is:
Can i drive the car with the CEL light on until the new sensor arrive?



Read the following threads:

F

Thread 'P0171 trouble code question'

26 March 2015

Hello,

So my P0171 engine code had popped up the other day. Ran a can of royal purple and engine code went away after the tankful of gas but unfortunately came back. Then my car started stuttering when engine is on load in 2nd and 3rd gear which seemed like an ignition problem. I changed the spark plugs and coil packs and it cured the stuttering and the engine code went away without any manual clearance of the code. After about a hundred miles it came back. What's going on!?

I searched and they said it could be a vacuum leak, MAP sensor, ignition issue, O2 sensor, fuel cap issue.. But I...

• Fugy
• Replies: 15
• Forum: NSX Owner Discussion (1st Gen)

Thread '"Solved" my engine sputtering/hesitation problem'

2 July 2011

Just wanted to share my happiness after finding the reason for my engine sputtering problem. First, I was certain that my problem was related to bad connection between the coils and spark plugs due to corrosion but since the problem was prominent at less than 4500 rpm I thought i'd try the fuel pump resistor bypass procedure and TADA! Silky-smooth operation through the entire register :biggrin:

So a new fuel pump will be ordered, I'm going for the Walbro.

I suggest all people who are having engine sputtering problems to try this REALLY easy 5 second test, just to exclude the fuel pump...

• mr_goat
• Replies: 37
• Forum: NSX Owner Discussion (1st Gen)

Post in thread '98 NSX-T Starts, idles but won't drive. CEL Multiple misfires due to fuel system malfunction.'

29 September 2023

Your car is OBDII. Did you use a code reader or the service check connector to determine that you had misfire codes? If so, what were the specific codes? If you had fuel supply problem causing lean misfires I would expect that you would eventually generate a fuel mixture out of range error code.

Main EFI relay failures tend to be "its working" / "its not working" failures. You are correct that it is a two in one relay containing a relay to power up the ECU and a separate relay to power up the fuel pump. It is possible that you have a bad electrical connections in the supply to...

• Old Guy

Thread 'Oxygen Sensors - Install'

21 July 2012

Hello,

Planning to replace all oxygen sensors. I have checked many threads and get confused with which sensors to buy in order to replace. NGK and Denso seems to be most everyones reccomendation.

What are the part numbers on these O2 sensors?

Also what kind of tools should be used? O2 wrench has been mentioned, but what kind and size?

Anyone seen a thread that gives step by step instructions on how to replace? Maybe with pics?

On a scale 1 tof 10 how diffcult is the job as a DIYer?

Thanks,

Jeff

• NSXRAY1
• Replies: 28
• Forum: NSX Do-It-Yourself (1st Gen)

 

[docjohn]

you most likely need your fuel injectors cleaned, bench flowed...worked for me.

 

[Old Guy]

The prior service and vehicle history if available can be useful information if you are asking for diagnostic opinions. They may alter the probability of such outcomes such as 'is it likely that my O2 sensor is dead'.

P01710 can be caused by a problem with the measurement device (the O2 sensor) or an actual engine problem which the measurement device has correctly measured. If the problem is a measurement device failure which means there is no actual engine problem (other than skewing the air fuel mixture to run rich) then you should be able to drive without issue. If the O2 sensor is jut fine then it is an actual engine problem and you may be 'less OK'. Depending on how less OK it is you can probably drive the car; but, I would not drive aggressively. You get to be the judge.

My first line of response would be to assume that the measurement device is OK and that there is an underlying engine problem. Particularly since you report idle issues which an O2 sensor reading lean would not necessarily cause. Since you are not getting a corresponding error on Bank 1 the MAP sensor and the fuel supply system are probably OK (a fuel pressure check is always a useful diagnostic). That kind of points a finger at a possible problem with the fuel injectors on bank 1 in which case following @docjohn 's suggestion to have the injectors tested and cleaned (all of them) would be a good idea.

At 100,000 miles it is possible that the O2 sensor has failed or that the injectors are dirty. If you knew the prior history of the car (it sat parked for 4 years with the same tank of skanky gas) that would cause me to adjust my probability way up on the 'its the injectors'.

 

[Ron1999]

Thanks for the comment, I like the thinking process to eliminate some options.
Some more context:

1. The car did seat for a long time before i purchased it, Last documented maintenance was 3000 miles ago, but in 2017.
2. I am still on the hunt for its service history (it was a Canadian car, even has NSXP 2009 stickers on it, with Toronto's skyline)
3. all filters and oils have been changed since got it

Another data point - when i drive the car with the AC on, no CEL or code apear (makes me think that it is running too lean)

will try to find a picture of the spark plugs i removed from the car.
will try running some injector cleaner first and will schedule a date to pull out the injectors and send them for proper cleaning.