I have a 2000 Mustang V6. I just changed the motor because the old one blew the rings and bearings. After putting new motor in I can't keep it running. I had the old motor rebuilt and they did a bad job. After install it knocked and and you could still hear bearing rattle. I wouldn't run unless I kept the engine around 3000rpm. I then bought a running motor and It still does the same thing minus the knock and bearing rattle. It misses bad and backfires out of the intake. I know I don't have the cam positioning sensor adjusted right but the garage told me it would still run without that but it would just run bad but it would at least be good enough to drive to him and have it set. There is compression gas and spark in all cylinders. The timing was never changed. The motor I put in was a 3.8 out of a 1997 cougar. I everything from my car from the heads up. All else is hooked up properly. I am thinking that there might be sensors that need adjusted but am open to any option. I would put it at 98% everything is right so if it sounds like i hooked up something wrong please tell me. I am about to loose my job for lack of vehicle and money is so tight I can't afford a garage so please help. I'll try anything.

 

Sorry about your job situation. Check the coil pack and plug wires. The CPS could be the main culprit here and needs to be fixed also. If you still have your coil pack from the old engine then swap the two and see if that helps.

 

Wait isn't the 97 cougar motor a single port?