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AZTechBrian
AZTechBrian, ASE Certified Technician
Category: Ford
Satisfied Customers: 708
Experience:  Owner
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I have a p303 code, very shaky under throttle and poor idle.

Customer Question

Hi, I have a p303 code, very shaky under throttle and poor idle. I tried swapping coil packs to no resolve. Spark plug is pretty new on cyl 3, looks ok when I took it out. Injectors were changed 4000 miles ago to refurbished ones. Any ideas?
Submitted: 1 year ago.
Category: Ford
Expert:  AZTechBrian replied 1 year ago.

So, you swapped coils and the cylinder 3 misfire returned?

Expert:  AZTechBrian replied 1 year ago.

Do you have a way of performing a compression test?

Customer: replied 1 year ago.
Yep, what I did was try 2 older coil packs that I had laying around from when I swapped all the coil packs 5k miles before.I don't have a compression gauge at hand but could get one.Any other ideas?
Expert:  AZTechBrian replied 1 year ago.

I know you said that the spark plug looks fine, but I would replace it anyway since I have seen on more than one occasion good looking plugs, even brand new out of the box cause misfires. If you have used multiple coils and keep getting a cyl 3 misfire, then the coil is not the problem. I doubt the injector is either. It could be rings, valves, valve springs, etc. First replace that plug just to make sure it's not that simple. Then do a compression test.

Expert:  AZTechBrian replied 1 year ago.

Please let me know what you come up with. I'll be around. thanks

Expert:  AZTechBrian replied 1 year ago.

How did it turn out?