tacoma fuel system problems
ryhe
03-07-2004, 11:19 PM
I can't seem to find the cause of my check engine light, trouble code P0171 lean condition. Keep resetting it. Keeps coming back. Anyone have any ideas? It's not the B1/S1 O2 sensor or MAF. Both are new.
I've got a '99 Tacoma, 3.4L V6 4WD 5sp, TRD supercharger, headers, & cat-back, smaller pulley running 11psi, water injection, larger injectors with APEX controller, and K&N FIPK, 90,000 miles. All mods have 50,000 miles on them.
I've read other postings that pointed to the O2 Sensor and MAF. My A/F ratio meter shows everything ok. I logged data with some OBDII software that showed the O2 sensor a bit slow responding, thus it's replacement. Airflow looked ok, but the MAF replacement was a "...might as well try, cleaning it didn't help".
The truck completely lays down when holding a steady 3000 rpm with little load, and the O2 sensor shows lean for a couple of seconds, then gets right back up again back to normal. OBD shows that the ECU turns on the FUEL CUT-OFF (stops the injectors), so that's what causes the motor to lay down, read lean, and trip the light, but why is the computer killing the fuel? Seems to me, it should not be killing fuel at 3000 rpm unless you back way out of the throttle. It's only supposed to kill fuel on deceleration to reduce emmissions. All other times the truck runs great! If it wasn't for the light keeping me from passing emmissions inspection, I'd ignore it (I've been troubleshooting it for quite a while).
I am also running 4.88 gears with 33's. I'm running a Superlift speedo calibrator that puts the mph right on the money. The computer shouldn't care that the vehicle speed vs. rpm is different from as-deliveredy from the factory (I think).
With all this giberish, anyone got any ideas? I'm out of 'em. thanks
I've got a '99 Tacoma, 3.4L V6 4WD 5sp, TRD supercharger, headers, & cat-back, smaller pulley running 11psi, water injection, larger injectors with APEX controller, and K&N FIPK, 90,000 miles. All mods have 50,000 miles on them.
I've read other postings that pointed to the O2 Sensor and MAF. My A/F ratio meter shows everything ok. I logged data with some OBDII software that showed the O2 sensor a bit slow responding, thus it's replacement. Airflow looked ok, but the MAF replacement was a "...might as well try, cleaning it didn't help".
The truck completely lays down when holding a steady 3000 rpm with little load, and the O2 sensor shows lean for a couple of seconds, then gets right back up again back to normal. OBD shows that the ECU turns on the FUEL CUT-OFF (stops the injectors), so that's what causes the motor to lay down, read lean, and trip the light, but why is the computer killing the fuel? Seems to me, it should not be killing fuel at 3000 rpm unless you back way out of the throttle. It's only supposed to kill fuel on deceleration to reduce emmissions. All other times the truck runs great! If it wasn't for the light keeping me from passing emmissions inspection, I'd ignore it (I've been troubleshooting it for quite a while).
I am also running 4.88 gears with 33's. I'm running a Superlift speedo calibrator that puts the mph right on the money. The computer shouldn't care that the vehicle speed vs. rpm is different from as-deliveredy from the factory (I think).
With all this giberish, anyone got any ideas? I'm out of 'em. thanks
Partyzant
11-08-2004, 10:18 PM
Having the exact same problem on a 98 2.4 I4. Nothing special in it just K&N FIPK. Replaced O2 sensors, MAF is fine. That damm light keeps coming back, I also can't get it smogged. My fuel consumption went down by 5mpg. Had a diagnostic done on it, they said my #3 valve is burned and seeping fuel into cylinder, stated that has they seen this problem on Taco's before. Don't have a definite answer for that. Anyone outthere got any ideas.
tacoma man.
11-09-2004, 03:14 PM
i replaced my o2 sensors too, my gas mileage was terrible and the CE light was on all the time i changed them and the problem was corrected.
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