I rebuilt an engine out of a 2001 XJ, to replace the original one out of my '92, after I blew it up and shot a rod out the side and bottom. Used all my old outer stuff off of my '92 on the 2001 block. I'm having an issue where when you try and start it it dies immediately unless, you keep the rpms at about 1000-1500rpms for awhile and it won't hardly idle. sometimes you have to kind of two foot it for about a mile then it runs fine. If you drive for awhile and it gets hot/warm it will die and not start until it cools down. You have to ease on the gas pedal otherwise it bogs down and dies, kinda like its flooding out. Any help is appreciated.

 

The no start when hot is often the CPS and/or coil. Assuming you have one and not the coil packs? Might also check the IAC for the cold idle problem.

 

I have just the one coil . And I will definintly check out the IAC and I just replaced the crank position sensor. The coil isn't that old either but it's a possibility.

 

As for the rough running did you check all the temperature sensors and the TPS to make sure they're reporting reasonable values? Also that MAP...

 

All the temp sensors are working great haven't checked the TPS yet. What are the symptoms of a bad ECM? I had a guy tell me his was doin the same stuff and that's what it was, after he replaced it ran great.

 

You are in supper company here with those above. With the 92 head and all it's sensors, the swap may well not be the issue. That MAP tube from the inside of the TB, back and up to the MAP on the firewall is supper crucial. Any crack or blockage will cause mixture issues. Something pretty easy to check.

I waz just wondering, could the old engine have "farted" enough to mess with the cat? Not likely I guess.

If you can ever see a change while/after jiggling the wires...there's that. Things move a little between hot and cold. On top in my signature is Cruisers tips. Checking ground resistance is always a good move.