Skip the auto shop - Our mechanics make house calls

Q: Code p0303 pulled cylinder 3 misfire

asked by on

Rough idle and poor gas mileage and cuts out bad between 40 and 45 mph Changed all plugs, coils, throttle position sensor, throttle body, air filter, maf sensor, fuel filter, gas cap, and have tested each fuel injector. Any other suggestions?

My car has 169000 miles.
My car has an automatic transmission.

Hello and thank you for contacting YourMechanic. With what you said about everything that you replaced on your F-150 5.4L, there is only one thing that will cause the problem that you are having. There is a Fuel Pump Delivery Module (FPDM) that delivers fuel from the fuel tank to the fuel rail. This is similar to the fuel pumps in other vehicles. Some Ford vehicles have a secondary FPDM above the spare tire under the bed of the truck. It is possible that the FPDM is not delivering pressure under a load. Try checking to see if the engine cuts out when heavily accelerated from a stop. If the engine cuts out then the FPDM is failing and should be replaced. If the vehicle is only cutting off at 40 to 45 mph, then there may have dirty fuel lines to it and needs cleaned. I recommend replacing the Fuel Pump Delivery Module, due to the mileage your vehicle has. This will cure the rough idle and poor gas mileage along with restoring power. Also, clean out the fuel lines with a small bristle brush. If you need assistance with this issue, a YourMechanic certified technician can come to your location to perform a car idle is rough inspection, confirm the repair needed, and provide you with any further assistance.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Truck won't start

If this is the factory light on the dash that says "theft" and is blinking fast, then your theft system is activated. You may need to try another key first after locking all of the doors and waiting a half...

Q: How do you check the transmission fluid?

Keeping an eye on your transmission fluid is vital. While you should follow Ford’s recommendations on scheduled services, you should also make sure you monitor the level of fluid in the transmission to prevent potential serious damage. Here’s what you...

Q: Bad oil pressure sensor

A common failure in your vehicle is the oil pressure sending unit. Once the sensor is replaced, these codes should go away. I would ask for help from one of the mechanics at YourMechanic to replace your oil pressure sensor...

Related articles

P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.