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Chris (aka- Moose)
Chris (aka- Moose), Technician
Category: Ford
Satisfied Customers: 44518
Experience:  16 years experience
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I have a 09 focus with a code po300 random misfire I have

Customer Question

I have a 09 focus with a code po300 random misfire I have changed the plugs checked for vacuum leaks and checked fuel pressure. the pressure when I first turn the key hits 60 psi and quickly drops to 50 psi then slowly continues to fall
Submitted: 12 months ago.
Category: Ford
Expert:  Chris (aka- Moose) replied 12 months ago.

Welcome, I'm Chris (aka Moose) I'm an independent contractor here at Just Answer.

Can you feel the misfires occurring?

Does it misfire at idle and while driving?

The fuel pressure spec is 55psi so there is a fuel pressure concern from pump issue if the pressure is going below this and falling.

Thanks for asking your question and letting me try to help you.

You should see a rating screen if I have posted an answer, not for an info request.

Your rating is my feedback. If I don't get feedback from customers, I will not be able to continue helping customers here.

Rating me good, bad, or not rating at all does not effect the fee you have paid nor does it close the post.

Follow up/Reply as many times as needed.

Customer: replied 12 months ago.
The engine is running rough worst at idle.
Expert:  Chris (aka- Moose) replied 12 months ago.

If you increase the rpm, does the fuel pressure increase?

Customer: replied 12 months ago.
sorry for the delay this is not my car it belongs to our youth pastor so I have to make arrangements to gain access. I retested the fuel pressure this time using an inline pressure gauge and my pressure is holding pretty steady at 60 pounds whether idling or accelerating. What would you suggest we try next?
Expert:  Chris (aka- Moose) replied 12 months ago.

Is there an rpm you can reach that is stops misfiring at?

Have you tried cleaning the MAF sensor and monitoring the CMP and CKP sensors for a hiccup in there reading?

Customer: replied 12 months ago.
The engine seems to smooth out when I'm running around 1200 rpms and above
Expert:  Chris (aka- Moose) replied 12 months ago.

Have you tried cleaning the MAF sensor and monitoring the CMP and CKP sensors for a hiccup in there reading?

What is the operating temp idle speed?

Customer: replied 11 months ago.
Thanks for your patience. My scan tool does not allow me to see any live data on either the crank or cam sensors. The operating temperature at idol after running awhile is 189 degrees.Is there any other way I can test the response on the cam and crank sensor.
Expert:  Chris (aka- Moose) replied 11 months ago.

A scan tool is the only way to know if the readings are good. A DVOM can check for signal presence but not if its accurate.