I have a 98 5.0 EB that is coding 0455. large leak. The gas gas is OK per Insp.
But I did notice that the smoke test port(green Cap 1lb max) was damaged. Could that have caused the code? The other thing I notice is when i go to fill the gas tank, i get no pressure release from the tank. My other cars both have a noticable vaccum release when opened.
Any thoughts would help.
Last item would the vaccum leak cause a 0430 code?
Thanks, Dedhead

I'm not sure if the smoke test port would potentially cause a P0455 diagnostic code. If you can find a scan tool that will display the CIDS/PIDS for you Explorer, you should run those and see what it says for the EVAP system.

As for the gas cap venting, I don't think you have an issue. I'm guessing that the other cars are imports. I've never noticed a venting gas cap on a domestic, but do find it on a fair number of imports. It seems like if the EVAP purge solenoid system is working properly, you wouldn't get the hiss from releasing the cap.

The factory service manual lists the following as potential causes for a P0430:
Possible causes:

-- Use of leaded fuel.

-- Oil contamination.

-- Cylinder misfiring.

-- Damaged HO2S.

-- Damaged ECT sensor.

-- Downstream HO2S wires improperly connected.

-- Fuel pressure too high.

-- Damaged exhaust system pipe.

-- Damaged exhaust manifold.

-- Damaged muffler/tailpipe assembly.

-- Damaged catalytic converter.

-Rod