03 GT Put used engine in and starts misfiring and breaking up under load

EBNS_2005

Member
Apr 27, 2025
3
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NC
Hey there i recently bought a 03 mustang with a blown engine i found a 06 cvpi engine and threw it in there and I'm getting a bunch of codes and the engine breaks up real bad under any sort of load. im paste the codes im getting below. Any help would be great
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Did you swap all the emissions controls over from your old engine or plug-n-play with the ‘06 controls?

Do you know if the codes existed previously either on your ‘03 or the donor?
 
Did you swap all the emissions controls over from your old engine or plug-n-play with the ‘06 controls?

Do you know if the codes existed previously either on

I swapped all the emission stuff so its all mustang parts and yes when i bought the car with the original engine before the swap it still ran those manufacture control codes
 
It should be a direct bolt in/replacement using mustang left over parts. There are likely issues that caused the original motor to blow. Start by testing the o2 circuits and maybe investigate if the ecm is tuned etc. I've put 4 crown vic motors in without issues (Well except for using the wrong spark plug wiring diagram on a 98 gt once haha). Made some good power on a stock 2012 crown vic motor and 9lbs of boost. 11.20's at 119 iirc.