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hello i have a 2003 ford focus with a p0302misfire and p0316 miss at start . under load or power brake it has a miss. I replaced plugs and wires about 6 months ago when there was no problem. I have replaced coil and still have the problem.I also cleaned injectors bye removing them and cleaned them .I installed #2 injector in#3 cylinder and still have #2 miss. See injector working with noid light. Also did compression check and have 150 per cylinder. Does sound light it might have a emissions tube leak but did not have a lift today to check it out. Any ideas out there ??? Thank you Robert
 

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Go after the 302 in terms of ignition. Swap the spark plug wire with another cylinder and the plug wire with another cylinder, keep track of what moved where, erase the code and drive the car again. When it comes back, if it moved to a different cylinder then whatever you moved to that cylinder is the culprit and should be replaced.

A strong and predictable miss under load is almost always ignition related.
 

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Also check the pigtail and connector for the coil.
 

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I had a bad coil do this to my wife's vehicle. I pulled the plugs, and found one burnt, but when I cleaned it or replaced it- it just kept burning up. I replaced the coil, and that solved the problem.

First things first: remove plugs. Clean, check gap, look at plug deposits. See if that cylinder has oddball deposits that give you an indication that something strange is going on in that cylinder- like red deposits. Move the plugs around like Jetrinka mentioned, and see what that does for you. If you have the same problem I did, then it will work for about a day before the misfire returns.

If your misfire is caused by spark plug wires, then it will reappear immediately unless a loose connection was the cause. This is one of the reasons I recommend lifetime plug wires for all daily drivers, you could've already changed those out for free and crossed that off the list of possible causes. I change plug wires whenever I feel like doing it.
 
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