1992 305 TBI, engine light flashes, but no code appears when I check it. Runs very rough, keeps bogging down, tach jumps all over the place.
I replaced the charcoal canister, the bypass valve, and the gas cap but it's still doing the same thing. When I take the gas cap off, there's absolutely zero pressure. I have no idea where to go from here. The fuel pump is new(ish) and the vehicle will keep running with gas pedal applied, so it's getting fuel.
Any ideas?

 

Get a fuel pressure gauge and post what your actual fuel pressure is

 

Checked the fuel pressure and it's just under 12psi. The book reads from 9-12psi, so it's good there. The car keeps bogging down. When I take the gas cap off, there's no pressure release at all. I have a new gas cap. Also changed the vapor canister, pressure valve, o2 sensor, idle air control valve, and the fuel pressure regulator. All cheap fixes, but still no resolution. Help!?

 

Take off the air cleaned and watch the injectors spray pattern. If its not a constant v then its possible they need serviced. Along what's your base.timing set at

 

The injectors are spraying fine, the TBI is new, along with the rest of the engine (has about 5000miles on it). The timing was set at whatever the factory setting is. When this first started happening, I thought the fuel filter was clogged so I changed it. The problem went away for about a day, then came back again. Now it's escalated to the point where it wont stay running and the tach jumps all over the place. The check engine light flashes as well, but no code shows up (12) when I check them. Usually when I take the gas cap off, I can hear pressure releasing. This doesn't happen anymore.