Misfire cylinder #3, right rear cylinder, 2015, 3.5L Eco boost. Code says "permanent". New plugs, swapped coils, still says P0303
permanent. I would thing a bad injector would throw a different code? Leaning towards the plug to the coil. Any ideas?

 

Common Problems That Trigger Code P0303

• Worn out spark plugs, ignition wires, coil(s), distributor cap and rotor (when applicable)
• Incorrect ignition timing
• Vacuum leak(s)
• Low or weak fuel pressure
• Improperly functioning EGR system
• Defective Mass Air Flow Sensor
• Defective Crankshaft and/or Camshaft Sensor
• Defective Throttle Position Sensor
• Mechanical engine problems (i.e.—low compression, leaking head gasket(s), or valve problems

 

Why not take it to a professional before throwing guesswork parts into it?

 

Many of the professionals today are nothing but glorified parts changers, based on what their equipment tells them. Real troubleshooting is somewhat of a lost art.

 

Wouldn't the sensors throw a separate code? Have replaced the plugs, swapped the coils (2-3) I am only getting a specific code for misfire cylinder #3?

 

The same with amateurs as you can see here on the forum every day.

 

Not at close to $200.00 per hour?

 

Well according to jkeaton's suggestions of possibilities you have another eight steps to take if you have the diag tools plus the parts needed to remedy the error code. I believe that code must be reset with a DIAG tool otherwise it stays permanent and won't go away. Guessing what parts to buy, and they should be Ford OEM parts, will be a daunting task and very expense.

Or you can not fix it at all and drive it like it is, and I wonder how long your engine will last with a misfiring cylinder. Sometimes you have to bite the bullet.

PS: There is an old proverb that states: If you think it's expensive to hire a professional to do the job, wait and see how expensive it is to have an amateur do it.

 

Wow yall are in a MOOD today. How unhelpful can we all be? Let's not find out. Let's try to be helpful!

• Worn out spark plugs, ignition wires, coil(s):
• (you changed plugs and coils wkth no cha ge, so it isnt those two, but chek the coil wiring for corrosion or damage)
• distributor cap and rotor (NOT applicable)
• Incorrect ignition timing
• (This is an easy check with a diag tool with live data, but it likely would be a misfire to the entire side at least, so if you don't have a tool, move on)
• Vacuum leak(s)
• (Easy check, grab a can or flammable break clean or other airsoal can, and spray around the engine bay. Listen for your engine speed to change while your are staying at vacuum. Lines. Don't be afraid to shake the vacuum lines gently while spraying.)
• Low or weak fuel pressure
• (This would be your injector, it's possible. I would start with a can of seafoam in the tank if the misfire isn't bad. Additionally, how new is your gas? Gas has a shelf life of about 3 months with its ethanol content these daya.)
• Improperly functioning EGR system
• (Possible, I'm not sure where the egr hits on your model, but this does typically throw an egr code.)
• Defective Mass Air Flow Sensor
• (Unlikely given it is only a single cylinder. But fairly easy to clean with a bottle of mass airflow sensor cleaner. And generally good maintenance. Worth a shot if nothing else is working)
• Defective Crankshaft and/or Camshaft Sensor
• (Would apply to a cylinder bank of misfires, not so much a single cylinder)
• Defective Throttle Position Sensor
• (Possible, but again would likely have multiple cylinder misfires or jump around and be inconsistent.)
• Mechanical engine problems (i.e.—low compression, leaking head gasket(s), or valve problems
• (Possible, but this is more of something you conclude after attempting the easiest things first. It is also almost always accompanied by ticking sounds and rough idles. And these jobs will become much more costly and labor intensive. They are doable by a diyer, but just understand you will likely still have a good chunk of change into it and a lot of time.)

now if you have any further information about what diag tools you may have available or other information you can supply such as does it misfire under load, at idle, etc,. Then at least so.e of us are willing to help brainstorm.