Help with CEL codes

[Semnos_NSX]

Hey guys, I just picked up my car from Autowave today. They did a great job fixing a few problems I had that included rebuilding the fuel pressure regulator, replacing the igniter, adjusting the valves and a few other things. After picking up the car, it ran great all the way back to work. After work, I pulled out of the parking lot and was at a stop light when the check engine light came on. When I got home, I pulled the codes and got these:
P0175……System to rich (bank 2)
P0172……System to rich (bank 1)
P0173……Fuel trim malfunction (bank 2)
P0170……Fuel trim malfunction (bank 1)

I did some research and think I have it narrowed down to either the cats or the O2 Sensor. Can anyone confirm this or shed some additional light on the subject? I am going to call Autowave back to talk to them, but will not be able to until Tuesday due to the holiday.

Thank you all in advance for your help!!

Steve

 

[Daedalus]

Not the cats. Probably not the O2 sensors, since the banks have individual sensors, and the odds of both failing at the same time is tiny. Besides, there are separate codes for bad O2s. What the codes are saying is that both banks are running so rich that they're beyond the ECU's ability to bring the A/F ratio back to ideal. Usually ECUs can trim up or down maybe 25% or so from nominal. If it was a single bank I would say perhaps leaking fuel injector. Since the fuel pressure regulator was just rebuilt I would check the vacuum line to the regulator first. If it's hooked up the next step would be to actually verify the fuel pressure to make sure it's right. Too-high fuel pressure would explain all the codes happening at once. Can't think of anything else that would, except for a huge fluke.

 

[Semnos_NSX]

Thank you Daedalus! I cleared all the codes and will take it for a drive today to see if it is just a fluke. If it is not, I will check the fuel pressure and so on. Thank you again.

 

[BioBanker]

I had somewhat similar codes (too lean instead of too rich, and only one bank) and the culpret was a secondary air injector that was leaking.

These air injectors, as I understand them, are downstream of the header and are used to inject air into the system to burn unburned fuel that reaches them.

Mine was leaking. Warrantied.

 

[Larry Bastanza]

Please tell us about exactly what setup you have. Since the Fuel Pressure Regulator was "rebuilt" is does not sound stock. CTSC?? Please fill us in.

I would agree with Daedalus and his comments. Sure sounds like the fuel pressure is too high or there is too much fuel for another reason. This is why we really need to know the setup, including engine management.

Regards,
LarryB

 

[Semnos_NSX]

The car is a 1999 and it has a CTSC on it with the high boost 9lb kit (old whipple style). It also has Comptech headers, exhaust and intake. I don’t have an after market engine management system as of yet so it is running off of the stock ECU. The fuel pressure regulator was rebuilt because the car was bogging at low RPM and Autowave determined that it was due to the diaphragm and spring in the regulator. As I said before, Autowave did a terrific job with the repairs but for some reason the check engine light came on after about 60 miles of driving it. I did reset the ECU on Friday and so far after one day of driving it, it has not come back on. I am definitely going to keep an eye on it but am a bit confused on why it came on…….was it a fluke or is it actually something?

 

[Daedalus]

Well heck, that is indeed a different ballgame. Are the injectors stock?

 

[Larry Bastanza]

The injectors are not stock for this setup. The best advise is to have Shane have a look. It does sound like maybe the fuel pressure is a bit on the high side though.

HTH,
LarryB

 

[Semnos_NSX]

Thanks Larry, I will call Shane on Tuesday.

 

[Daedalus]

Sounds like a wonderful excuse to get an AEM or similar.