Once finished with the heater core replacement the jeep only starts if I hold the throttle then once it starts it will only stay idling with the throttle applied then after a little while it will run like normal on its own.. this only happens once a while. Any idea what it could be? Like I said it started to happen right after the heater core replacement. Also once it gets running it’s good for the day and it happens randomly about the next day after sitting for a while