REVIEWS
What a Misfire Actually Is
Each cylinder in the RDX has a spark plug, and each plug has its own ignition coil feeding it. The coil builds the high voltage that makes the spark, and that spark lights the fuel. When a coil starts to fail, its cylinder doesn't fire cleanly, and that missed firing is the misfire. You feel it as a shake, because the engine's trying to run down a cylinder.
A weak coil is at its worst when the engine's cold. Starting a cold engine takes more from the ignition system, so a coil that's marginal fails to fire right at startup, then recovers enough to run okay once things warm up.
Why Coils Fail
Coils live in a hot, vibrating spot right on top of the engine, and that environment wears them down over the years. The insulation inside breaks down, and eventually the coil can't make a strong spark. High miles and age are the usual setup for it.
Signs a coil's going on the RDX:
- A rough idle or shake, worst right after a cold start
- A check engine light, often flashing during the misfire
- A stumble or hesitation when you accelerate
- The roughness fading as the engine warms up
- A misfire code naming a specific cylinder
A flashing check engine light deserves quick attention. It means the engine's actively misfiring, and raw fuel reaching the exhaust can cook the catalytic converter, which is a much pricier fix than a coil.
Coils and Plugs Go Together
Here's something worth knowing. A worn spark plug makes a coil work harder, since the spark has a wider gap to jump, and that strain wears the coil out faster. So a misfire that looks like a bad coil can really be tired plugs dragging the coils down. That's why these often get checked and replaced as a pair rather than one at a time.
How We Track It Down
We scan for codes, since a misfire usually names the cylinder. We check the coil and the plug on that cylinder first, because they're the common cause and the cheaper thing to rule out. If those are fine, we look at the injector and test for a vacuum leak. Then you get a straight answer on what's causing the misfire, instead of swapping parts and hoping.
Smooth Out the Cold Starts
A misfire gets worse as it runs, and a flashing light can take your catalytic converter with it. Bring your RDX to Driven Auto Care of Castro Valley and we'll find what's behind the cold start shake before it grows into a bigger bill. Reach out to set up a misfire diagnosis and feel better about your vehicle.
