backfiring in engine compartment under load

[basbol13]

I been having a problem with backfiring in the engine compartment when I put a load on the engine from a stop. This occurs whether the car is cold or hot. It also occasionally happens when I accelerate a low speed. I have changed the plugs, wires and distributor cap. I've also run injector cleaner through the motor and checked to see if all injectors are working.

I'm stumped can anyone help me?

1978 280z 2+2

[Walter Moore]

What is the overall condition of the engine? Could you need a valve job, or has the head been reworked recently?

Have you checked the timing?

[basbol13]

Less than 40,000 on the motor.

Figured out it is the AFM took it apart and cleaned inside and connectors works fine now.