Debugging Isn’t an Obvious or Easy Skill

I tend to take it for granted and I imagine most of you do as well, but not everyone is good at debugging and/or troubleshooting. I was reminded of this – again – recently when I had some issues with my truck. It started with the ‘check engine’ light coming on. I didn’t see any obvious problems so I took it to the local repair shop we’ve used for years. It turned out to be something simple, just a failed PCV hose, about a $200 repair and the check engine light went dark again.

All was good, until I drove away. When I stopped at a traffic light the engine bogged down and almost stalled, then it seemed to cycle from about 500 rpms up to about 900 rpm, then back down to 500 again across a few second interval. I called them, but it was Saturday and I’d have to wait until Monday for them to look at it again, meaning I’d have to rent a car, etc, etc. I decided to just drive until the next Saturday so I could drop it off Friday night.

The problem continued during the week, dropped it off,Saturday afternoon they called to say it was ready – ready because they couldn’t duplicate the problem. By the time I got there it was late and on the drive home,yes, same problem still happening. Reschedule for the next Saturday to try again.

Repeat again, this time they call me early, I go over and they tell me that the plugs are worn, I should replace the plugs and wires. This bothers me. The truck ran fine before the repair, not fine after, that doesn’t seem like bad plugs. Their theory is that the bad hose was masking the problem. Or it could be some blower motor, which they’ve removed and cleaned and seems fine, but maybe not. I compromise and replace the plugs (which had to be done at some point anyway), delayed on the wires because it felt like upsell.

Same problem on the test drive. Take it back, later in the day they call me to say it’s not doing it any more. Drive again, seems fine.

I didn’t press, but I’m assuming they got something wrong on the initial repair. To me it’s debug 101 – ask the question, what changed, what got touched? I couldn’t get them to see that the odds of something being related to that change were far higher than the chance that some other part decided to fail at the same time.

Do I think they suck? No. Within the boundaries of normal repairs the service has been good or better, pricing is good, and it’s close to home. But I do know that when I start hearing “we’re not sure” that it’s time for a second opinion because I’m not going to get them to see it from a different view.

Troubleshooting does take practice, but it also takes a mindset. It’s an easy leap for some to get there, almost impossible for others, requiring a combination of letting go of your pride in sticking to the first solution and an ability to step back and see the whole picture.