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Category: Ford
Satisfied Customers: 26089
Experience:  ASE CERTIFIED TECHNICIAN ADVANCED LEVEL SPECIALIST. Wisconsin certified emissions state inspector
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Misfiring under part throttle...after what build date in

Customer Question

Misfiring under part throttle...after what build date in 2004...did fuel rail pressure increase from 39-41psi to 60-65 psi?
JA: Has the vehicle turned into a gas hog? And how does it start -- same as usual?
Customer: Starts fine...just put new air filter dash says I get 18.1 mph hiway
JA: What is the model of your '04 Ford?
Customer: Eddie Bauer AWD 4.6 V8...175,000 miles
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: Snap on scanner reads 39 psi KOER...41 PSI KOEO. and yes I would like to fix myself
JA: Anything else you want the mechanic to know before I connect you?
Customer: Changed fuel filter once 2 wks ago...what was inside the filter was disgusting
Submitted: 10 months ago.
Category: Ford
Expert:  AMEDEE replied 10 months ago.

Hello and welcome!

My name isCustomerand I can assist you with your question.

Expert:  AMEDEE replied 10 months ago.

Is the check engine light on? Are there any codes in the computer?

What parts have been replaced for this misfire condition?

Customer: replied 10 months ago.
Fuel filter and air filter...chek engine light is on.. 3 codes...misfire at startup....random misfire detected... And cyl.5 misfire
Customer: replied 10 months ago.
Hello? Are you there?
Expert:  AMEDEE replied 10 months ago.

Thank you for that information. YES, I am still here

Expert:  AMEDEE replied 10 months ago.

The most common cause of this misfire condition would be bad spark plugs and or ignition coils. These fail all of the time causing the engine to misfire. If these have not been replaced as of yet, this would be your next step. You can also disable the EGR valve and drive the vehicle to see if the misfire is gone. If so, it is related to the EGR system. Another possible cause would be a bad oxygen sensor or even a programming issue with the PCM. You may want to have it checked for the latest software available

Customer: replied 10 months ago.
Can u tell me what my fuel rail pressure should be? When we pulled fuel filter last wk the filters contents were nasty..I'm thinking the pump may be tired at 175000 miles..and after trying to push fuel thru a plugged filter for so long. Book says frp should be between 60-65. Psi and I show 39..but its an 04 could it be that I have a late 03 fuel system?
Expert:  AMEDEE replied 10 months ago.

According to my specs, it should be between 34 and 45 psi

Customer: replied 10 months ago.
Ok one last question...I have a Lang mechanical fuel injection pressure tester..and the ford EFI adapter to go with it..but where do i make the connections? The adapter has a spring lock connection and a qc connection
Expert:  AMEDEE replied 10 months ago.

Thers is usually a fuel pressure test port on the fuel rail. If not, you would need to tap into the fuel pressure line going to the fuel rail using the correct adapaters