On the 99 jeep grand cherokee I6 4.0, when you change the coil pack, you need to change wiring to coil pack. Switch wires in the plug and directly reverse them. Right to far left, outside left ti far right, and then reverse the two middle wires the same way. The coil wiring to the new coil pack was changed on the after market coil pack. So current plug wiring won't work. I had a shop do this to mine after replacing coil pack twice, changing cam shaft sensor, crankshaft sensor was fine, compression was fine. Was getting plenty of fuel. All computer tests were good. Same with plugs and wires. All grounds were cleaned and remounted. Must do this when changing coil pack. Save yourself some time and money. We wired in a secondary plug that the wires were switched, in with the current existing plug. Basically made our own adapter plug for aftermarket coil. Truck fired right up. Save yourself 300.00 in labor fees by simply doing this adapter plug yourself.
Sunday, August 30th, 2020 AT 10:40 AM