Hey I have a 90 yj that had the stock 4.2 when I bought it the previous owner had put a 4.0 jasper motor in it cause he wanted fuel injection which is great but now I'm in a dilemma when I start the car in the morning (cold start) you have to let it warm up for like 5-10 min and even then it still stalls out from time to time now were not sure if its not getting the pressure in the fuel system or its not getting a strong enough spark if anyone knows what the problem is please let me know