Im stumped. If anyone would take the time to read this and shoot any ideas I’d be eternally grateful 🫡

**2005 LJ 4.0 swapped into 2000 XJ - Cranks, almost starts, won’t run. Running out of ideas.**

**Setup:**  
2000 Jeep Cherokee XJ  
2005 LJ/TJ 4.0 long block  
Using 2000 PCM  
2000 engine harness  
2000 intake manifold  
2000 fuel rail  
2000 injectors  
2000 coil rail  
2000 CPS  
2000 flexplate  
Complete 2000 OPDA/synchronizer installed in the 2005 block  
**Symptoms:**  
Cranks normally.  
Occasionally sounds like it wants to start for a second but never runs.  
Sometimes coughs/backfires through the intake/exhaust and sounds like the engine is breathing incorrectly.  
No sustained idle.  
**What I’ve verified:**  
Fuel:  
49-50 psi while priming/cranking.  
All six injectors pulse with a noid light.  
Injectors removed from the rail all spray fuel (no obvious clogged or dead injectors).  
Injector firing order observed as 1-5-3-6-2-4.  
Ignition:  
Spark present.  
Tach moves while cranking.  
Using 2000 CPS with 2000 flexplate.  
Compression:  
Approximately 150 psi on cylinders #1 and #6.  
Have not checked the remaining four yet.  
Mechanical timing:  
Removed timing cover.  
Timing chain appears in good condition.  
Cam and crank timing dots line up correctly.  
Verified chain pin/rivet count per Haynes manual  
Valve train inspected.  
Pushrods seated.  
Rockers and springs appear normal.  
OPDA:  
Complete 2000 OPDA installed.  
Internals have never been disassembled.  
Reinstalled multiple times using #1 compression TDC and alignment pin procedure.  
Also verified after rotating the engine two full crank revolutions.  
Things already ruled out:  
Fuel pressure.  
Injector pulse.  
Dead injectors.  
Wrong flexplate.  
Wrong CPS.  
Weak battery.  
Obvious timing chain installation error.

The only thing still bothering me is the engine sounds like it’s trying to pull air through the intake/exhaust at the wrong time. It almost behaves like it’s 180° out, but I cannot find evidence that it actually is.  
Has anyone run into something similar on a 2005-to-2000 4.0 swap? Is there something unique about the 2005 cam/crank/OPDA relationship that I’m overlooking, or is there another test you’d perform before I start tearing into it again?

Is there a way to just take the timing chain off and set the timing completely over just to eliminate the possibility ? Thank you!

Timing issue (possibly?)