Cylinder 3 Misfire Detected

2012 Audi Q5 view of engine with hood popped

About a week ago, the check engine light on my beat-up, hand-me-down, 12-year-old Audi Q5 lit itself up on my way home from work. To be honest, it wasn't much of a surprise, given a sudden inability accelerate on an incline without stuttering like an old dune buggy.

Clearly something was wrong, but the car has 150,000 miles on it, so when I bought it off my dad I also knew I was buying all of the problems that caused him to sell me the car for practically nothing in the first place.

Now, I don't know a damn thing about cars. I've always considered myself more of a "software person," so the realm of the physical kind of scares the shit out of me. But, 2024 is a year where I want learn to be more comfortable working with my hands than my fingers, so an old car in mediocre condition seemed to be just the motivation I needed to skill up.

Diagnostically Speaking

So, as soon as I got home, the first thing I did was order a cheap OBDII scanner on Amazon.

I don't know much about cars, but I do know enough to understand that most cars built after 1995 have a port underneath the steering column that allows mechanics to scan the vehicle for digital codes to understand why the check engine light turned on.

Thanks to a hybrid work situation, I was able to let my car sit in the driveway while I waited for my sensor to arrive, and when it did I plugged it in and was informed that my check engine light (and the accompanying stuttering) was due to a P0303 trouble code (otherwise known as a "cylinder 3 misfire").

With that information in mind, I did what every good nerd would do next, and proceeded to Ask Jeeves "what is a cylinder 3 misfire?" (and also "what is a cylinder?" because "car dummy" here). While there were a number of potential causes, my research informed me that it was most likely either a bad spark plug ("what is a spark plug?") and/or a bad ignition coil ("what is an ignition coil"?).

Now that I had my information, I enrolled in YouTube University to see what it looked like to actually replace spark plugs and ignition coils in my exact car, and then gave my sister-in-law a call (who used to be an auto technician) and asked her if she'd provide some adult supervision while I groped around inside a bunch of mechanical stuff I barely understood.

Maintenance, Baby

A few days later, I had a set of new spark plugs and an ignition coil in hand, and a very faint idea of what to do with them.

Turns out, my car was designed to be easily maintained (which, I have been informed, is not the case with a lot of cars). The biggest trouble we had was unlatching the plastic clips that connected to the ignition coils. In the videos I watched, the clips had some flex in them to make unlatching fairly easy, but in my car (due to probably come combination of the age, and the wide swings in temperature variability in Colorado), the plastic was a lot more brittleā€”I did not make it out of that experience without chipping a few pieces of plastic right off.

Once we got the ignition coils disconnected, everything else was pretty straight forward.

My teacher (and, let's be honest, babysitter) showed me how to pull out each coil, clean them, and inspect them for damage (the 3rd cylinder coil was "fouled," as expected), and then walked me through the process of removing, "gapping" (which I understand the purpose of, but don't have the energy to describe right now), and replacing each spark plug.

The Friends We Made along the Way...

The biggest challenge wasn't the actual act of maintenance, but the little annoyances that come up along the way. Plastic clips that won't unlatch, spark plugs that won't release the wrench, the fucking wind, and the fact that Audi put the battery underneath every single thing in the trunk, including the spare tire.

For about $90 and two hours of my time, I not only saved what would have amounted to $300-$500 at my regular mechanic (and still probably 2-3 hours of my time), but now I have a little extra knowledge and skill in my toolbelt for when I need to (or decide to) replace the other three ignition coils in the future.

Subjectively, my car now seems to be running a lot better than it has in a while, and starts up a hell of a lot faster than it did before. While the gearheads out there are probably rolling their eyes at this trivial maintenance, I am proud of not fucking my car up, and the experience has given me just a little more confidence for the next time something goes wrong.


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This is post 035 of #100DaysToOffload