Fiero runs really bad

ROBERTP3270

MEMBER
PONTIAC FIERO

My 1987 Pontiac Fiero Coupe w/2.5 tech 4 w/ electronic ignition w/automatic w/ 87,000 on rebuilt motor, just started running really BAD and the check engine light came on and I run the codes and it coded 25; The local dealership says no code for 4 cylinder and it meant I had a bad computer, I have replaced the computer and the throttle position sensor and still it run really BAD and black smokes and stalls. HELP! Rob

1 Reply

MMPRINCE3000

MECHANIC
133 POSTS

Code 25 (MAT sensor) applies to the V6. Recheck the code.
When a sensor is bad (MAP, TPS, Coolant etc.) The ECM will set a default value. This is always rich to prevent a lean condition and engine damage (although extended rich condition will also cause damage).
Grounding terminals A and B of the ALDL (engine off, ignition on) will cause the SES light to display the code(s).
First it will flash code 12 (3 times, flash. Pause. Flash, flash), then all error codes (3 times). When all error codes have been displayed the SES light will again display code 12.

More than likely you have a bad sensor, see if Autozone, Advance etc. Can scan the computer for you and isolate the problem.