Help!! Misfiring After Install of Remanufactured 3.7L Engine

[mercury83]

I recently swapped a high mileage 3.7l ford engine for a remanufactured 3.7l ford engine in my 2011 v6. It included new spark plugs. When I got the car back, the check engine light started to flash and read misfires on two cylinders. It only happened when I aggressively accelerated on the highway, leading a mechanic to suspect bad coil packs.

We then immediately replaced four of those coils including the ones connected with the cylinders mentioned in the code. For a day it was fine, then the check engine light came back on and the misfiring became more noticeable and consistent. When I had the code read, it said misfire in cylinder 3 (one of the replaced coils), and a random misfire. Before we replaced the coils it would blink until I pulled over and stopped and restarted the car, then it would disappear. After those replacements it stays on and the car bucks and is constantly misfiring. It can’t reach high rpm’s and it vibrates on idle. I have all new spark plugs and 4 new coils. Whatever the issue is I’m suspecting it’s electrical/computer based. I’m badly in need of ideas because I’m not a mechanic and I can’t afford to keep throwing money at this. Any ideas on what this could be?

 

[JmP6889928]

Did your old engine misfire? What was the reason for the replacement? I never put new plugs in a rebuild-I always use plugs I know were firing correctly before and drive it a while until the break in is complete and then change for new. New plugs can be a blessing and a curse, because you always think "these are new plugs, they can't be bad", but that's not always the case.

I would remove all plugs and take a reading. If one or more are wet, they you have other issues which could be valve seals or even piston rings that haven't sealed as of yet.