A misfiring engine is the most common engine complaint and the coil is always the number one suspect. But finding the coil can sometimes cause some head scratching.
Ignition coils are commonly located on the cam/rocker cover which is on the uppermost of the engine. To access the ignition coils, first remove the aesthetic plastic engine cover.
In this post you’ll understand where your coil is located and how to replace them.
Location Of Ignition Coil
Most gas powered engines today use independent coils known as COP or coil on plug. As it sounds, a coil is fitted directly over each spark plug. If your engine is an eight cylinder, you’ll have eight coils, one per cylinder. A six cylinder will have six coils and so on. The coils are identical, they’re not cylinder specific.
I say most engines because older engines may use a wasted spark type system or a coil pack. The wasted spark type system uses just one coil between two cylinders, so your eight cylinder will have just four coils, six cylinders just three coils and so on.
Wasted coils may be located on the engine rocker/cam cover just like modern COP systems or they may be fitted remotely. By remotely, I mean close by but not directly over the plug. When remotely fitted they will obviously have a short plug wire fitted.
The coil pack is a pack of coils combined (molded) in one unit. It is fitted directly onto the spark plugs just like the COP system.
Coil packs are located directly on top of the engine cam cover. Coil packs were expensive, if just one coil failed the complete pack needed to be replaced.
Removing the Engine Cover
To access an ignition coil, simply remove the plastic engine cover. Nearly all manufacturers employ a tough black plastic cover to conceal the engine. The covers are generally aesthetically pleasing, some manufacturers go to the trouble of molding in some mock engine detailing, which I find a little ironic.
But the cover has other functions, it helps suppress engine noise and helps protect engine components from moisture and grit.
Most covers are tool less removal, simply pull up firmly to remove. But before doing so, just check for fasteners or press clips. Be careful removing plastic components if temperatures are well below, plastic shatters like glass, now how do I know that?
Replacing A Coil
As car repair goes, you’ve won the lottery. Replacing a coil is by far the easiest fix for a misfiring engine and it’s a common failure too. Just know, it’s not uncommon for some of the other coils to fail soon too.
To remove a COP type coil, simply remove the aforementioned plastic engine cover and then remove the electrical plug connector. The electrical plug connector will have a release tab and in addition may have a locking tab.
To release the locking tab, slide the plastic lock, press the tab and pull the connector firmly by the plastic housing, never by the wiring.
Now remove the COP fastener, usually one or two bolts and that’s it. Pull firmly on the coil to remove.
- Check the spark plug bore for pooling oil. It’s a common cause of misfiring and it’s root cause is a failed cam cover gasket.
- Lube the COP socket with dielectric grease before fitting the coil, promotes continuity and makes life easy for the next time you need to remove it, if there’s a next time.
- When fitting the coil electrical connector, listen for the click, that means it’s home and seated correctly.
- Replace the plastic engine cover – its important, helps protect the coils from moisture and debris.
That’s it, you’re a pro!
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