I have a 2003 with a stubling 4.6
this is acting line when I change the elbow on the back of the manifold. But that is ok.

the only codes are a 308, and 300.

It is also hard to start in the morning. Any ideas where to start?
150K miles

thanks
doug

 

Verify the fuel pressure

 

Cylinder #8 (back one on driver's side) is misfiring. That's the reason for the stumbling.

 

P0300 is multiple cylinder misfires - that's why I'd verify the fuel pressure, as the fuel pressure effects all cylinders, just like the elbow on the back effects all cylinders.

On the other hand, Alloro is usually right . . . . .

 

Not according to my wife!

 

Sounds normal.

 

Me too, What should the fuel pressure be? And I am assuing I check it at the test port on the line that holds the injectors

 

About 45 PSI and yes you test it at the fuel rail as you described.

 

fuel pressure is 43. Seems to run better after running it hard but it now comes and goes.
I was thinking I would replace the PCV valve, Can you tell me where that is? Also after I reset the codes, it has not had any come back, but has a few moments where it stumbles, then runs fine. Also when it stumbles there is no power, and if you floor it, and get to about 60, it starts running fine again?
Thanks for the help so far.

 

Top middle of the passenger side valve cover.

 

I pulled that hose and it is just a fitting on the valve cover on both sides.
This is a 4.6 if that matters.
Thanks

 

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Engine Performance problem 2003 Ford Expedition V8 Two Wheel Drive Automatic