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Discussion Starter · #1 ·
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
 

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did you just replace your battery? could be a map sensor or IAC or AIT sensor... when a vehicle is cold and acting up like this its either a dirty Tbody, a dirty or broken Idle Air Controller, or Air Intake Temp sensor... these are all very important to a cold vehicle! Is it idling really low to begin with?
 

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leak on the intake, making it run very lean
 

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Discussion Starter · #6 ·
Thanks for the help everyone when they did the swap they ran aftermarket gauges and instead of having the coolant temp sensor in the thermostat housing they were only running the aftermarket gauge and the computer didn't know how to react in turn pretty much shutting down the truck
 
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