Hi I'm new to this forum. I have owned my 2004 WJ 4.0 for some time, and have drawn from the useful information here many times in the past, but now I have an issue I can't seem to find the answer to:

I have a 2004 Grand Cherokee. The engine is going bad after an oil sump failure, and resulting engine seize. It had 190K and already suffered bad blow-by, and low compression. When the engine seized, I was able to get it going again but... It is time for a new engine.

I decided to buy a used engine to run for a year or two, while I save up and build my core to eventually put back in (buy a kit here, get some machine work there, etc.) so I bought a 60K mile motor out of a 2003 LJ that got a V8 swap. I read on this forum that the WJ and TJ use the same Vin "S" long block, and I reasoned that the LJ (same engine bay as the TJ and also Vin S) would be the same as well. And... It looks like I'm mostly right.

The motor I bought still had everything on it, all the serpentine stuff, wiring harness, injection, intake, exhaust manifold, mounts, distributor, etc. However, when I started looking everything over, I began to notice differences: The mounts are different, but no biggy, I can see that the block has threaded holes to fit my mounts, then I noticed something I consider more sinister; the wiring harnesses are different. Most Noticeably in the section around the main ground to the block, the way the starter is grounded, the connection to the alternator, and the connection to the distributor... Speaking of which, the distributors are way different: The '03 LJ has a big disk analog distributor, and the '04 WJ has small one, which I suspect is digital. So the question is, should I be able to drop in my old '04 WJ distributor into the '03 LJ block, and use the my '04 WJ wiring harness, or should I try to use the '03 LJ distributor and the wiring harness that came with the '03 engine?

 

Welcome to CF!

It's my opinion you should use all the sensors and the distributor from your engine, wrap up the LJ harnesses and put them on the shelf or sell them. Your PCM is programmed to read all your original sensors and might get confused with any others.

BUT....That's my opinion.

 

Thanks Dave. I have been thinking on it, and I agree. I believe that the block is the same between the two engines, but not everything else is, SO I will default to using auxiliary parts off my old engine, unless the part is exactly the same and in better shape on my new motor. After thinking on it, I think it is safe to assume that if the blocks are the same, the cams are as well, and I should be able to drop the digital distributor in place of the analog one on the new motor. I'll pull both distributors and make sure they have the same spline on them.