renix xj runs bad - really need some help

Hello all-

I've go a 1990 xj Auto trans. I bought it with a blown motor, put a junkyard comanche motor in and it ran fine for a month. After the first time I ever held it at wide open throttle from 0-65 it started running very badly. It starts and idles fine and sounds like it is running good while you accelerate but will just barely run at a constant speed going down the road. I've been working on this for two weeks and am stumped.

So far I have:
replaced and adjusted TPS
replaced CPS
checked MAP sensor - good
checked temp sensor - good
checked all engine ground connections
checked fuel pressure - 39 PSI w/o vacuum 31 with vacuum
replaced plugs and wires
swapped in a good set of fuel injectors from another motor
replaced fuel filter

The plugs look like they have a lot of carbon on them. If I had to guess from looking at them I am running too rich but I don't know why.

Does anybody have any guesses where I need to look next?

Thanks

Running rich is a common sympton with a bad 02 sensor...
.

that fuel pressure looks like it's a couple of points low...maybe i'm just not remembering mine correctly.....

try cleaning out the throttle body behind the acs and TPS.

unplug the map sensor vacuum while running and see if it fluctuates

I changed the O2 sensor, no change.

swapped the entire throttle body from my old motor. still doing the same thing.

I've never had to take a vehicle to a dealer to get it fixed but I'm about out of ideas.:smsoap: Anybody got any more suggestions?

your motor is worn out

Check for a vacuum leak. Look closely around the intake gasket and EGR valve.