migillicuty
Probationary Member
- 1
- 0
- Jul 20, 2012
-
Riverton,
Vermont
Hey new to the site and I searched the forums for specifics of my issue with no success. My 420a is a 98 and its built all forged, ported 1mm valves t-3 turbo and at the moment doing 9 psi boost with 310cc injectors. 12:1 vortech (not for long hopefully) 255hp walbro.
Ok so to the issue. The car runs great when cold but once coolant temps hit about 150 it seems to go into closed loop and run crappy. I hooked up a live data tool and the long term fuel trim when cold is -0.87%. When its warm (hits 150 according to the scanner) it drops to -18% to -25% which to my understanding means its running rich so the computer is trying to take away fuel hence the stalling and bogging during idle but it overcompensates and makes it run lean. I have a wideband that reads about 16.1 during a stalling or bogging then the car revs itself back up and the a/f goes to 12-13 sometimes and then tries to settle at 14.7 and then repeats. I have a new 02 sensor so I know thats ok. Any ideas how to fix this? Could a map sensor cause this with open and closed loop? I have checked for vacuum leeks and not found any. Plus if it was a vacuum leek it would idle bad when cold. Fuel pressure is at 30psi and seems like that may still be too high since the computer is cutting fuel. I checked the reference voltage to the map sensor and its 3.8 volts coming out of the ecu. Is this bad? Its also 3.8 at the map sensor as well so I know the reference wire is good. Any input is greatly appreciated thank you!
Ok so to the issue. The car runs great when cold but once coolant temps hit about 150 it seems to go into closed loop and run crappy. I hooked up a live data tool and the long term fuel trim when cold is -0.87%. When its warm (hits 150 according to the scanner) it drops to -18% to -25% which to my understanding means its running rich so the computer is trying to take away fuel hence the stalling and bogging during idle but it overcompensates and makes it run lean. I have a wideband that reads about 16.1 during a stalling or bogging then the car revs itself back up and the a/f goes to 12-13 sometimes and then tries to settle at 14.7 and then repeats. I have a new 02 sensor so I know thats ok. Any ideas how to fix this? Could a map sensor cause this with open and closed loop? I have checked for vacuum leeks and not found any. Plus if it was a vacuum leek it would idle bad when cold. Fuel pressure is at 30psi and seems like that may still be too high since the computer is cutting fuel. I checked the reference voltage to the map sensor and its 3.8 volts coming out of the ecu. Is this bad? Its also 3.8 at the map sensor as well so I know the reference wire is good. Any input is greatly appreciated thank you!
