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Are there any ticking noises on the passenger side of the engine while it is idling and missing?
Ok. Swap the coil and then the spark plug between cylinder #2 and see if the code changes to #2 cylinder. If it is still #1, it could be a bad injector or a rocker arm (Ford calls them followers) fell off.
Your engine has three valves per cylinder. If a follower fell off, you wouldn't notice it till you put a load on the engine.
The P0351 is a coil driver failure for cylinder #1. Where are you getting the coils for your engine?
Ok. Use a test light and disconnect #1 coil and start the engine and check for power on the RED wire and a pulsed ground on the other wire in the connector while the engine is running.
It could be a bad coil. I do not recommend the aftermarket coils. But you have to use what you can afford and I completely understand that. Take one of the coils back and get a replacement one. Then retest the system. If the codes return, especially the P0351, the PCM (Engine Computer) will have to be replaced. The coil drivers are built into the PCM.
Does the noise change when you change one of the settings on the AC controls?
You might want to swap the injectors between #1 and #2. You could have a slightly clogged injector. Swap them before replacing it.
It could be an electronic mode door motor for the AC system. Fully open the glove box and get the clicking noise to start and check the motors around the evaporato case under the dash. You will feel the clicking noise from one of the motors.
Ok. Just reply back when your ready.
Check for power and ground to the injector the same way as the coil. See if you get constant power on the Red wire and a pulsed ground on the other.
I have done a few also. But getting 99% constant is odd. You may want to check the converters also for that bank.
I would do a manual compression test on the engine and compare the readings to#2, 3 and 4.
Sorry, I meant to do a manual compression test on #1 and then do that entire side and compare the readings. This will evaluate the mechanical parts of the engine without taking it apart.
A compression test will check for sticking valves and bad piston rings. The compression on each cylinder should be 175 psi.