Engine runs rough and backfires after warm-up

[wheelie-schizes]

My 454 TBI starts and idles low, but after about 2 minutes (once it warms up), it starts backfiring through the air filter and won’t take throttle.

Here’s what I’ve done trying to fix it:
- Replaced spark plugs, wires, ignition coil
- New distributor (installed by someone else)
- New fuel injectors and fuel pressure regulator
- Also found the EGR valve was loose and leaking — I resealed and tightened it

Timing is set to around 4° BTDC, but it’s hard to adjust properly because it seems to shift on its own.
There’s no vacuum advance on the distributor, so I assume timing is electronically controlled.

**Do I need to disconnect the timing advance wire when setting base timing?**
Any input or ideas are appreciated!

 

[Ricko1966]

My 454 TBI starts and idles low, but after about 2 minutes (once it warms up), it starts backfiring through the air filter and won’t take throttle.

Here’s what I’ve done trying to fix it:
- Replaced spark plugs, wires, ignition coil
- New distributor (installed by someone else)
- New fuel injectors and fuel pressure regulator
- Also found the EGR valve was loose and leaking — I resealed and tightened it

Timing is set to around 4° BTDC, but it’s hard to adjust properly because it seems to shift on its own.
There’s no vacuum advance on the distributor, so I assume timing is electronically controlled.

**Do I need to disconnect the timing advance wire when setting base timing?**
Any input or ideas are appreciated!

Yes you need to disconnect the set timing connector. When,how and why did it start backfiring? Have you actually checked fuel pressure?

 

[Ricko1966]

Okay does it run okay cold? Cold it's in open loop. Warm it's in closed loop,I'd start by testing my sensors.