2000 Nissan Xterra rough idle

Is the smoke black? Also, is the engine from the same year, make and model vehicle?

2000 xterra 3.3 6cyl 4 wheel drive. The motor is from a 02 xterra the only difference I know of is the intake. The smoke is white /gray color real rich smelling

White smoke usually indicates coolant it getting into the combustion chamber. Are you sure the intake fit properly and sealed? Also, there could be a bad head gasket.

Was going to check the coolant when I get home. I hope it's not a cracked head was a pain doing that motor don't want to do it again

Just got home cranked my truck and started smoking went to the back put my hand over the exhaust and my hand smells like fuel and had moisture on it.. Also I put two gallons of gasoline in it,its only run for about an hour and I'm back on Empty again

Do you have access to a live time scanner? I have to be honest, moisture is normal from the exhaust. White smoke isn't. It sounds like coolant, but maybe there is an issue with something like the coolant temp sensor. If it tells the computer the temp is colder than it is, the computer will dump fuel to compensate. There also could be a leaking fuel injector. Have you checked fuel pump pressure to make sure the regulator is doing its job?

Since it is using so much fuel, I am questioning if it is running too rich. I have to be honest, a rich mixture usually causes black smoke from the exhaust.

Do you have access to a live time scanner? I have to be honest, moisture is normal from the exhaust. White smoke isn't. It sounds like coolant, but maybe there is an issue with something like the coolant temp sensor. If it tells the computer the temp is colder than it is, the computer will dump fuel to compensate. There also could be a leaking fuel injector. Have you checked fuel pump pressure to make sure the regulator is doing its job?

Since it is using so much fuel, I am questioning if it is running too rich. I have to be honest, a rich mixture usually causes black smoke from the exhaust.

NOTE: I am assuming that all the original sensors have been installed in the same locations on the new engine.

I have a scanner that goes to my phone and I only know how to get the codes Wich is throwing a knock sensor and cps. The cps is brand new and KS won't cause any of these problems, u planned in swapping my injectors from my old motor this weekend, I'll change the temp sensor tonight when I get home from work

I got to thinking I put my old temp sensor on the new motor cause the other one was broken off

Check to see if the injectors have the same part number. I thought you switch them.

It's still smoking really b.ad I'm at a loss I don't wanna put another motor in I'm ready to drive my truck again I just hope I didn't do all this work for nothing.. You know of any thing else it could be

Something is causing it to dump fuel. From here, it is difficult other than the things I suggested.

I know it is hard with out looking at it, thanks for all the help appreciate it