My LT1 seems like its missing, after it idles down. First thing is , the motor wont Idle down properly,Installed both new temp senders. After I kick it down so it idles properly, The engine runs rough, seems like it misses, but its fine under load it seems. I noticed alot of carbon coming from the right tail pipe, on the floor.
I just put this motor in the car , and I know it ran great in the other car. The only thing I done to the motor was put plugs and wires on it.I checked and rechecked the wires, and All my connections. Any Ideas??

 

It may help if you posted some specifics about the car; year, mods, etc.
Did you use the same PCM from the car the motor ran great in or the one that was in your car? If from your car, are they the same or did the one from the other car perhaps have a tune programmed into it?

 

My car is a 96 Fleetwood, no mods. The new engine is out of a 96 Roadmaster. Everything was the same. I used the Fleetwood PCM. I drove the Roadmaster for a couple days (appr.300 miles). So I know everything worked well.
I posted this problem on the Cadillac forums, and the only reply I got was "take it to your local dealership".

 

The very first thing to do is look for dead cylinders since it runs bad right from the start. Obviously you should start with the "black" side first.

I think you have 2 wires crossed but don't realize it.

 

I checked all my wires again today and they were all good, so I started pulling plugs, the whole right side were BLACK, couldnt even tell where they were sparking on the resistor. I put new plugs in that side and it ran fine until she loaded up again. I pulled the plugs again and they were black again. should I try to un hook the 02 sensors? Or what could be doing this

 

Sure, try unhooking an O2. See if it runs better.

Did you happen to notice before if it ran ok until it went into closed loop?

 

The engine does run good until it goes into closed loop, but as soon as its warm it starts missing or whatever its doing.

 

I unhooked both sensors on the right side, one at a time. Neither one made a difference, Still "loading up" on the right side.Also getting terrible gas milage. I tried swapping the MAF, didnt help?

 

Its finally running right, When I installed the motor, I had the wiring harness for the o2 sensors crossed from side to side, I was burning rich on the right side, but I had the o2 wires for that side plugged into the left bank. \
Thanks to everyone who had suggestions