Beware the tune-up diagnostic
Back in the day, when internal-combustion engines started to sputter, refuse to start easily or stumble and stall, some senior mechanic would always chime in with, “she just needs a tune-up.”
For our daily drivers, at the very least this meant swapping out spark plugs, air and fuel filters, cleaning and adjusting the carburetor, replacing ignition points and verifying the engine timing. Sometimes, new spark plug wires were required as well. However, all this went the way of the dinosaur in the 1980s, with the arrival of fuel injection.
Some shops still use the term. For some, it’s an honest slip of the tongue, but for others, it can mean a repair bill full of things your vehicle might not need.
If you take your vehicle in to your mechanic to diagnose a problem and they suggest a “tune-up” before even looking at it, you may be at the wrong place. Don’t agree to a tune-up even after they’ve checked things out, unless they detail exactly what they intend to do and why.
The first thing to say no to is any type of injection-system cleaning, or “power purge.” This won’t actually correct any running faults, and is only recommended by the chemical suppliers as preventive maintenance. Most experts agree it’s of questionable value.
If anyone suggests replacing the spark plugs, ask about your car’s recommended replacement intervals. Many vehicles use long-life platinumor iridium-tipped plugs rated for 100,000 kilometres or longer. Replacing them just because they’re fouled will only take care of the symptom, and only temporarily.
Almost any engine problem will trigger a check-engine light. The only way to get to the bottom of the problem is to start by running the tests related to that code. About the only exceptions are mechanical failures, such as a defective valve lifter or camshaft or poor quality fuel. It’s worth noting these particular faults will sometimes trigger a code, but not always.
Watch out for the throttle-body-cleaning upsell. In early fuel-injection systems that placed the injectors — usually one or two — at the bottom of the throttle body, gasoline vapours could gum up the works.
The varnish-like buildup on these older units could cause the throttle plate to stick. Cleaning with special chemicals and a brush was often necessary, and it solved a world of running faults. But most of today’s engines use individual injectors for each cylinder, and they’re located far enough away from the throttle body to almost totally eliminate this condition.
You don’t necessarily have to suspect your technician when they say your ride needs a tune-up, but don’t be shy about asking what exactly they’re going to tune up.