I had a 2002 4.7L HO rebuilt and cant get it to run due to a problem that nobody seems to know how to fix or where to start. Here's what happens. Start the truck and it runs good for about a minute or so. As soon as the ECU looks at the o2 sensor it begins to run rough and backfires like its lean. The codes say it's and intermittent crank/cam sensor. both sensors have been replaced. The wheel on the the cam has been replaced. The tone wheel on the crank has been checked. The complete wire harness has been replaced. ECU has been traded for a used known working ECU. The crank was turned and straightened. It's almost like the crank is twisted or something although nobody has ever seen that happen. I have $4000 plus in building the motor and don't even know what to try at this point. Can anybody help???

 

Have you checked the fuel pressure, changed the fuel filter if it has one? Maybe unplug the O2 sensors to see if it changes what it's doing? I'm assuming the O2 sensors are working?

What exhaust is on it? If it's running open pipes, it can wreak havoc with the computer control.