Should I replace all my coils or just the ones misfiring?

Maintenance/Repairs
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1

2002 Audi A4 V6/3.0L w/ 80k miles



Its due for its first major tune up. The check engine light has been on for a while. My mechanic says that the diagnostics report a mis-fire on cylinders 2 & 4, and this is usually cased by bad “coil-packs”.



Since I’m going to have him do the tune up anyway, should I have him replace ALL SIX of my coil packs, or just the coils for cylinders 2 & 4?



Thanks All!



-PH

2

If you can access the coils packs easily you should consider replacing all of them if you can do it yourself. It is easy IF you can see the coil packs. Sometimes they are just below a cover that is quickly removed.

The coil packs can be pricey and paying list price and the mechanic’s markup even pricier. If your mechanic does the job just replace the two. If you can do it, then you can do all 6.

3

Usually one coil pack feeds two cylinders. If 2&4 are serviced by the same coil pack, then I would replace only that one IF it is checked and is in fact bad. They are pretty reliable and should last he life of the vehicle, but occasionally one will go bad.

I really think the problem is something other than the coil packs. Your engine would be almost undrivable if you had two cylinders misfiring due to coil packs. The misfire would be constant. I suspect your misfire is intermittent and could be due to other reasons, like needing a “tune-up”.

4

I would leave the good ones in. If electrical components survive the “infant mortality” stage, they tend to last nearly forever. You actually can reduce the reliability of the car by replacing proven good coils with un-proven brand new ones.