My brother & I were swapping a motor that we were told was a '97 into my '96 Cavy.

We noticed some of the sensors were different (the plugins) & my old motor ('96) had a sensor going into the front of the oil pan. The '97 didn't have this.

Long story short; we couldn't get it to run right.

We switched all the sensors & the oil pan over, but we couldn't get the motor to idle. It would run (got very hot) if we held the throttle open.

We were told by the JY that a '97 motor should work in a '96.

Has anybody run into this problem or have any idea what went wrong?

Those are the same... or 90% the same depending on the platform it was installed in, auto/man trans, options, etc. Either way, the major parts are the same.

Buying a used engine from a scrapyard and slappin' it in will usually cause all kinds of headaches though. I am not sure what was wrong with the original engine, but your best bet is to just swap the parts you know need to be replaced. If you spun a main bearing or something to that effect, just use the scrapyard block, and swap everything over from the original. This way you can visually inspect the inside of the engine. (these things can often be in worse shape that the engine you have already, god only knows how long its been sitting out back rusting away. or how they got there in the first place) Not to mention replace rotting gaskets and seals which usually come back to haunt you later.

If you think the engine was in good shape or done the above... double... tripple check all connections and make sure everything is in place. No matter how many times you do this kind of thing, you always have a chance of over looking something obvious.

Other than that, I can't really help you. It could be any number of things, but good luck reguardless.