xj 91, spark dies, PLEASE HELP!!??

Hey guys!
I'm from Norway so excuse my bad english....

I have this 91 xj,4.0,Lim.,auto. and I have'nt been able to start the damn thing for 8 weeks!!!! I have tried almost anything, also measured the signals from both the CPS and Sync sensor with oscilloscope, seems to be good signals even at the input terminal at pcm, tried to changed the pcm, measured coil, changed rotor, cap, plug wires etc. Tested compression!
Also tried various settings for the distributor/rotor assembly!
I've also tried to short out the ASD and fuelrelay to get increased gas pressure.
It's just like its going to start, then dies after 1 sec and when I look at the spark, it seems to be one good spark and then it "fades" to just rarely one bad spark occasionally.
Desperately seeking answer????????

How many miles? Have you changed any sensors lately?...If not try replacing the CPS. It could also be the coil.

In Norway a CPS is about 500$ and I have to order it, it's not a warehouse item ... and I have tested and measured coil and both positionsensors!
Mileage is about 150k.

Please help!!!!

Have you changed coil wire may be breaking down Do you have spark at both coil wire and plugs Have you checked camshaft sensor in dritributor. badge714
questions holler [email protected]

My guess is IAC (Idle Air Controller) on the back of the throttle body - that's what it was on mine - same symptom. Luckily I have 2 91's in the driveway so I was able to swap parts and get a diagnosis. However, after looking at 3 different IACs at the parts stores ($40) and noticing the brass ends were significantly different than OEM , I'm off to the dealer to pay about $80 for one. . .