Jim Grant's Tech Tips
‘94 Jeep Grand Cherokee, Too Many Coils
Q: I own a ‘94 Jeep Grand Cherokee. It was idling very slow and couldn’t figure out why. I replaced the plugs wires and fuel filter but, still idled slow. I sent it to a mechanic who replaced the ignition coil and distributor pick up and it ran fine for one day. I took it to work and when I went to leave it wouldn’t start. I checked it and there was no spark so I took it back to the mechanic and he said the new coil went bad. He replaced it and it ran for 2 days then I went to drive it home from work and it wouldn’t start. I purchased another coil myself installed it and it fired right up. Do you have any idea why it’s burning up the coils?
A: Before replacing the coil too many more times you may want to go the Jeep dealer and buy an updated ignition coil and harness. The ignition coils were known for shorting internally, causing a variety of running problems. The update called for a lower internal resistance coil and a modification to the wiring harness that included an external resistor. If you’re installing an aftermarket coil that has a lower internal resistance without the wiring harness modification you’ll just keep burning out ignition coils.