So, the mighty ‘94 Buick Century has been parked for some time because it’s been going through a bout of insanity - it will randomly and abruptly switch between “runs just fine” and “I think it’s missing two cylinders”.

My dad finally got it hooked up to his OBDI scan tool during one of its moods. What he got out of it was troubling:

  • It thought the intake air temp was -20F (ambient was 65F).
  • It had a 3V reference signal from the throttle position sensor.
  • The PROM ID listed in the computer was 1.
  • The “target RPM” at idle it had listed was zero.

If you unplugged the throttle position sensor, it would start running normally for about 20 seconds before it would compensate and start running like shit again.

Dad said he tried a couple fuel injectors - unplugging #4 made it run better, unplugging #3 caused it to stall instantly.

I think it’s time to replace the computer, and call an exorcist.