Jim Grant's Tech Tips
01 Lincoln LS, Misfire Computer Codes
My son’s 01 Lincoln LS just started to misfire and the check engine light came on. The computer was scanned and it had a cylinder #1 misfire code. The code was erased and #1 was swapped with #3 cylinder. Testing of the car now shows two codes that are pending and they’re cylinders # 1 & 5 misfire. What’s going on?
- Leslie Mangali
You should first focus on the #1 cylinder misfire code. So, just what part was swapped? If all you moved was the spark plug from #1 cylinder to #3 cylinder and the computer is still coming back with a #1 cylinder misfire code, then you’ll want to inspect the ignition coil and the spark plug boot for that cylinder. So, our readers know, this vehicle has an ignition coil for each cylinder for the engine. Each coil has a short rubber type boot that connects it to the spark plug. One of the more common problems we see with this ignition system design is caused by the rubber boot from the coil to the spark plug failing. The spark from the coil will burn a small pinhole through the rubber boot. This allows the spark to by-pass the spark plug. This pin hole is hard to see and just removing and installing the coil and boot can change the condition for a short time. The computer doesn’t know that the boot has failed; all it knows is that the engine has misfired. Now if you swapped the coil, boot and spark plug from #1 to #3 cylinder and still have a code for a misfire in cylinder #1 then you have other problems that may be mechanical or electrical to that cylinder. As for cylinder #5? Isn’t it great that a cylinder on the opposite side of the engine that you were working on now has a problem? We call that Murphy’s Law, if it can go wrong, it will, even if you didn’t touch it. Keep your focus on cylinder #1. Once you correct that you may find that cylinder #5 was a phantom code that the computer threw in there just to keep you on your toes.