Ran into a bit of an issue today while progressing with my swap. A little background:

Car is a 2000 XJ with standard federal emissions equipment. Header, downpipe, car, etc are all in good shape so I was planning to reuse them when I swap the engine in from my donor car, which is a California emissions car. If I were just swapping out the engine, I know this wouldn't be a problem, but the car I'm swapping into suffered an engine fire and I am using the full harness from my donor car.

If I use the computer from my original car and just leave the extra O2 sensors unplugged, will the car notice anything is different? Also, are the manual and auto computers interchangeable or specific to the trans? I can't remember reading whether they just did engine control or trans as well. If thats the case, I suppose I'll have to find a computer from a manual federal emmisions car.. Any help would be great!

If you're using the harness and computer for a CA standard, you need all the O2 sensors hooked up. I am not even sure if you can use a CA standard harness with a Federal standard computer or vice versa. Without all of the necessary O2 sensors installed and working properly your computer won't know the air/fuel ratio your engine is running and either run too rich or too lean and cause you problems. I suggest you stick to factory spec here and grab a like harness from the JY.

That's what I thought I might hear. It may be simpler for me to just stick with the California emissions at this point. Finding an intact harness at the junkyard and removing it may be more trouble than it's worth. I was already going to have to replace the exhaust from the cat back so what's another $200 for a California emissions precat set? Thanks for the help.