Diagnose Procedure For Recurring Cylinder 1 Misfire After Coil Swap?

[Turboguy]

Ok so this thread covers a cylinder 1 misfire I got recently after only 3,000 miles on new coils. There was no oil on coil, plug or in well, but I replaced visteon coil with motorcraft coil and new plug and it was fine for a month.
Now 500 miles later, cyl 1 misfire has returned along with 420/430 low efficiency cat codes. Car is hard to start when warm also, and last year a backfire blew out the back of the intake manifold.
What would the correct diagnostic procedure be now? Fuel pressure test for leaky injector/replace injector #1? (70,000 miles on em). And what else should I check: injector wiring etc?
Please advise!

 

[msgtusmc]

Ok so this thread covers a cylinder 1 misfire I got recently after only 3,000 miles on new coils. There was no oil on coil, plug or in well, but I replaced visteon coil with motorcraft coil and new plug and it was fine for a month.
Now 500 miles later, cyl 1 misfire has returned along with 420/430 low efficiency cat codes. Car is hard to start when warm also, and last year a backfire blew out the back of the intake manifold.
What would the correct diagnostic procedure be now? Fuel pressure test for leaky injector/replace injector #1? (70,000 miles on em). And what else should I check: injector wiring etc?
Please advise!

V6 or V8? Replaced intake manifold? NOID tester can be rented from auto parts stores to check injector connectors voltage, use the Ford or Bosch adapter. Try swapping the injectors to see if problem moves. Swap plugs then if no results from injectors. Ensure fuel pressure is correct. When was the fuel filter changed?

 

[Turboguy]

Thanks msgtusmc,

V8
Blown manifold replaced with used factory piece
Fuel filter changed recently, only a few thousand miles ago
Will track down that tool and do the injector swap.