Before July 2008 I never had a car that included a check engine light. The Porsche 911 I bought that year has one, but I never saw it come on while driving in the more than seven years since then. But last Friday, we came out from shopping, started the car and there it was, still shining at me after the car had finished the boot-up process of ensuring that everything was in order with the car. I drove half a mile to a gas station, got out the manual and looked up the check engine light. It advised taking the car to a mechanic to check it out. And it said that if the light started blinking, it might be best NOT to drive the car until it was sorted out. Of course I was worried about disaster scenarios, not loose gas caps. I had filled up with gas and knew the gas cap was on securely.
We drove a little over a mile to get home. Along the way, the light remained on but started blinking briefly two times, only very briefly. It was after 5:00 pm and Tony Heyer, my trusted Porsche mechanic, was already closed, not to open again until Tuesday. I had a troubled Friday night, tossing and turning, and then managed to put it mostly out of my mind for the weekend. I talked on the phone with Tony on Tuesday and got some reassurance that I'd probably be able to drive it to his shop. Early Wednesday morning I was driving the seventy miles to Tony's shop. I was really worried that the light might start blinking, but it did not.
Mystery is the worst part. Is it something minor like bad plugs or more major, even a blown head gasket? Well it seemed to be driving just fine, so blown head gasket wasn't likely. It did seem to be running a little bit rough, but I wasn't even sure of that. Idling at 800 rpm, the tachometer needle was jiggling a bit, but I didn't know whether it was excessive. I arrived at Tony's right on schedule for a 10:00 am appointment. Soon I would know what it is. Whatever it is, I knew Tony could fix it.
After a fifteen minute or so wait, Tony plugged his computer into the car. He fiddled with the computer a bit, and thankfully, gave no gasps of alarm. He walked away briefly to attend to something else and I quickly took a peek on the computer screen. There were four lines of text and each one contained the word "misfire." Misfire! Well that didn't sound too disastrous and it also seemed to fit that feeling I had had about it running a little rough.
Tony came back and asked me, "So did it seem like the car was running rough at all?" Welllllll, yesss!! I had even mentioned this to him when we talked on the phone on Tuesday. Yes, he remembered that. He looked on his computer at the history of my car's maintenance and then told me he wanted to check the coils on the spark plugs. The plugs only had nine thousand miles on them, so they were probably just fine. But he had no record that we had ever replaced the ignition coils. They last a long time, but it had been long enough that they might need replacement.
He had Wes get the car up on the rack, put a fan on the engine to cool it down, and when it was cool enough, he started pulling the six coils. It gets really hot inside the engine where the coils sit and eventually (maybe 60,000 miles) the plastic housing begins to degrade, with tiny cracks appearing. The electrical charge can then make it out through those cracks, shorting against the metal casing of the engine. That is a misfire! Sure enough, there were some cracks in the plastic housing of my coils.
Soon my car had six new coils installed. Wes took it out for a test drive, saying it was fine when he returned. When Tony came back from lunch, he took it for a test drive too, confirming all was well. After some chatting with Tony and Wes, I was soon on my way. I did a little U-turn in the parking lot to make my way toward the street and in that thirty feet of driving it was immediately obvious to me that the car was driving sooooooo much better, smooth as could be! I stopped and called out to Wes, thanking him for his work.
After a scary start, the Check Engine Light was my friend in the end, not a digital gadget torturing me with a mystery about my car. It had detected a problem before the problem was even obvious to me as the driver. In the old days a car would be obviously shaking and in need of a tune-up before we would know to take it in to the shop. The Porsche technology helped me get the car tuned up beautifully, long before I could detect even the slightest ruffle in the driving of the car.