[Mayson]

So I have a 1994 f150 with a 302 5.0 in it. I'm trying to fix it but I'm stumped it is backfiring out of the intake when I go past half throttle but any less it is fine.

I already changed the spark plugs and checked that the distributor was connected right.

 

[COP TZR]

Lean(vacuum leak) or timing.
Timing spout reinstalled?
Stock ecu with no chip?

 

[Mayson]

Yeah it is totally stock

 

[Top Heavy]

So I have a 1994 f150 with a 302 5.0 in it. I'm trying to fix it but I'm stumped it is backfiring out of the intake when I go past half throttle but any less it is fine.

I already changed the spark plugs and checked that the distributor was connected right.

I agree with @COP TZR - If you have "backfiring" out of the intake, its either running very lean and is "popping" audibly out the intake or really backfiring which is a signal that the plugs are firing out of timing while the intake valve is open.

The cause could be a multitude of things, check the distributor, check the Hall Effect signal, check the ignition module, then check fuel supply (if popping).

Was the distributor taken out previoulsy?

 

[Mayson]

No the Distributor has never been removed

 

[Top Heavy]

No the Distributor has never been removed

Check the Hall Effect Sensor and ensure fuel pressure/supply

Is the engine actually backfiring, or is it "popping" audibly through the intake through throttle transition?

 

[Mayson]

It is "popping"

 

[Top Heavy]

It is "popping"

When was the last time the fuel filter was replaced?

Have you verified fuel pressure?

Is it the original fuel pump?

 

[Mayson]

When was the last time the fuel filter was replaced?

Have you verified fuel pressure?

Is it the original fuel pump?

I'm not sure I need to check all the because it was sitting for a couple years.

 

[Top Heavy]

Typically a popping out of the intake under throttle transition or higher demand fuel condition leads to a lean condition.

 

[COP TZR]

I'm not sure I need to check all the because it was sitting for a couple years.

This is important information for the start of this post.
Can get into fuel pump, fuel pump sending unit hose, regulator, clogged or malfunctioning injector, stuck cylinder head valve, etc...

 

[stangjumper]

I'm not sure I need to check all the because it was sitting for a couple years.

More the reason those need to be checked