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So I didn't know about the issues these vehicles have before doing this but traded a 01 mustang gt for a 05 mercury mariner premier v6. So the day I got the vehicle it was dead so we jump started the vehicle which it started up perfectly, ran perfectly, no check engine light nothing. The very next day I drove roughly 80miles and all of a sudden I get a check engine light and the check emissions system reading on my dash which went away after restarting my vehicle. I drive roughly 5miles and the battery light comes on with the abs light but no check engine light so I replaced my alternator which was bad on the vehicle. After replacing the alternator I start my vehicle up and all of a sudden the vehicle is misfiring at a steady rate so I started and unstarted the vehicle 2-3 times same issue but on the 3rd attempt I get a check engine light with the battery light on and abs light on again then my vehicle just stalls out and then wouldn't restart. Got my code reader and got the notorious codes for ignition coils 1,2,3,&6 which stated ignition circuit open or shorted to ground and a bad ecm. Well after 2 days of messing with the vehicle and getting a crank no start I got underneath the vehicle and see that my throttle position sensor, and crank shaft position sensors are caked in oil so I pull them out and clean the hell out of them and the fittings they go into. Low and behold the vehicle starts up but only stays running with me giving it gas. I still get the same check engine light same codes. So if the coil packs caused my ecm to go bad wouldn't my vehicle still not of started up? Maybe its it's no the ecm but the crankshaft position sensor or my throttle position sensor causing the misfiring and horrible running engine?
 

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Welcome to the FFO!

What are the actual codes?
How many miles on the vehicle?
How long have you owned it?

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Diagnose the issue first
P0356 FORD Ignition Coil 'F' Primary/Secondary Circuit (With Video) (autocodes.com)

The power to all is 5 volts
The PCM grounds each coil to fire the coil

The PCM uses the crankshaft position sensor to signal the PCM to fire off the coil. If that CPS has been oil fouled it may be giving bad trigger signals.

PCM is an extremely rare failure. Like winning the lotto. More than 50% of the PCMs sent back as a core return are good.

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One last piece, at 202K on the clock, it is very likely the O2 sensors are at the end of life. This impacts the fuel side of the engine not the ignition. But you need a good feedback from the O2 sensors for the PCM to send the correct amount of fuel to the cylinder.

If the vehicle has been neglected, make sure air and fuel filters are fresh. Along with newer spark plugs.

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