98 4.0 EFI all Cylinders Misfire

[Galileopisa]

I recently purchased this explorer Had a code test done and got a P0301 -P0306 codes for misfire on all 6 cylinders.
so far I have got spark plugs, plug wires, fuel filter, pcv valve. I know these are basic replacement parts and was going to replace them anyways. but what else should I look in to having checked?

 

[ranger7ltr]

Check your fuel pressure...

Replacing the fuel filter, if it is clogged or if the fuel pressure is low, is a good start as replacement...Your fuel pressures' specification is 30-45 psi for the return line type of Ford fuel system...And since there is a vacuum line attached to the fuel pressure regulator the higher the vacuum, the lower the fuel pressure...

 

[swetrid]

Intake gaskets could be a problem if it is high mileage.

 

[KBarbina]

Were there any other trouble codes stored? I'm inclined to think it's lean fuel delivery as well, but your oxygen sensors should pick that up......

 

[Galileopisa]

Changed wires, plugs and fuel filter. Now it has the lean fuel and a random misfire. It runs fine at times but will still have a rough idle at times.

 

[ranger7ltr]

I should have asked before...

What are the numbers of the codes you are getting now? Are they P0171/P0174? And do you have the SOHC engine?

If yes on both you probably have an intake leak at the junction between the heads and the lower intake...or between the lower and upper intake...

Oh and what is the fuel pressure reading now after changing the filter?

 

[Galileopisa]

Will have to get back to u on those. As for the motor not sure. Its a 4.0 and the vin is an X model

 

[ranger7ltr]

That's cool... And on the engine by the vin code x you have an OHV 4.0 liter...