Greetings. I am new to this board and Im at my wits end trying to fix a 95 P30 truck with a 454 tbi (engine code N)

my troubles began when the fuel pump went bad and was replaced with a delphi oem unit. The inline filter was also replaced and the engine started but idled really rough. The engine misses and backfires thru the tbi and stalls most of the time. Ive replaced the pickup coil, the control module.TPS, MAP, Intake gaskets, timing chain, IAC, O2 sensor, water temp sensor, plugs, wires and have done an ECM swap with new ecm unit.
The only way i can get the engine to idle is to disconnect the vacuum line to the MAP sensor and if i reconnect that same vacuum line while the engine is running the engine stalls.

I dont know what else to do to solve the problem and I was hoping that some of you could please help! Im really going crazy here trying to pin this thing down
Ive triple checked the timing, checked every connection on the harness from the ecm to every sensor plug and everything checks good

thanks
Denis

 

The board Thirdgen.org is for '82 through '92 f-body vehicles (Firebird & Camaro). There is some lee-way in this if it is related to these vehicles. Unfortunately your post is far from that vehicle group.

The fullsizechevy.com board may have some better information. If anyone has suggestions to fixing his vehicle please PM Denis65.

RBob.