Lot AP1991TAMLB664: 1991 Pontiac Firebird Trans AM

The 1991 Trans Am’s Tuned Port Injection (TPI) system is generally reliable, but after 35+ years, a few issues show up repeatedly:

Top 5 Common Problems:

1. Fuel Pressure Regulator Failure - The diaphragm inside the regulator tears, causing fuel pressure to drop from the required 40-45 PSI down to the 30s. This leads to hard starting, especially when warm, and rough idle. The listing mentions this car has a new fuel pump and sending unit, but doesn’t specify if the regulator was replaced.

2. Leaking Fuel Injectors - The original Bosch injectors develop internal leaks or get clogged. This causes fuel pressure to bleed off overnight (hard start), rough idle, and poor fuel economy. Many owners replace the entire injector set when restoring these cars.

3. ECM (Computer) Failure - The 1989-1992 speed-density ECMs are notorious for dying, especially in hot engine bays. When they fail, you’ll get random stalling, no-start conditions, or weird drivability issues that seem like sensor problems.

4. Idle Air Control (IAC) Valve Issues - Carbon buildup makes the IAC stick, causing erratic idle, stalling at stops, or the engine racing at idle. This is usually a $50 fix with a new IAC valve.

5. Fuel Pump/Wiring Problems - The in-tank pumps last about 100-150k miles, but the connectors often fail first. The listing shows this car has a new fuel tank, pump, and sending unit - smart preventive maintenance!

Good news: Most of these are affordable fixes ($50-200 each), and the TPI system is actually quite robust once sorted. The 1991 models with the 305 (like this convertible) are generally more reliable than the high-performance 350 versions since they run lower compression and less aggressive timing.

Would you like me to help you find similar Trans Ams, or do you have questions about any specific TPI issues?