A check-engine light that blinks on a shaking CX-5 can look like the same warning you have seen before, only more insistent. It is a different reading altogether. Blinking marks a misfire heavy enough to overheat and damage the catalytic converter. The shake you feel at idle and the stumble as you pull away come from that same missing cylinder.
Fuel that cylinder fails to burn enters the exhaust and burns inside the converter. If the light flashes while your CX-5 shakes, pull over as soon as it is safe and arrange to have it brought in. At Precision Auto Care in San Leandro, we trace that miss to the part behind it for drivers from San Lorenzo. Your repair plan then names that part and the test that found it.
One Coil Sits on Each Spark Plug
The Skyactiv-G 2.0 and 2.5 engines in the CX-5 carry four ignition coils, one sitting directly on top of each spark plug. Each coil turns battery voltage into the high voltage that jumps the gap at the tip of its plug. That spark lights the fuel and air in the cylinder. Because every cylinder has its own coil, one cylinder can stop firing while the other three keep running. You feel that missing cylinder as an uneven shake through the seat at a stop, and as a hesitation when you accelerate away.
Moving the Coil Settles It
Our ASE-certified technicians start with a computer scan of the engine. A misfire code can name the one cylinder that is missing, while a random-misfire code means the miss is not tied to a single cylinder. With a random code, the likely suspects are the parts all four cylinders share. Even when the code names one cylinder, the coil and the plug beneath it are both suspects, and so is the wiring that feeds them. Any of them can stop the spark, and each feels the same from the driver's seat.
So we pull the coil from the misfiring cylinder and swap it with the coil from a cylinder that runs clean. Then we run the engine and scan again. The coil is at fault when the misfire moves with it. If it stays where it was, the cause lies elsewhere, such as the plug or the wiring. We replace the coil that carried the misfire with it. When the miss stays put, we move on to the plug and the connector at that cylinder.
The 2.5T Runs Its Plugs on a Shorter Schedule
Mazda's 2.5T turbo engine came to the CX-5 for the 2019 model year. Its spark plugs are due every 40,000 miles, against 75,000 miles for the non-turbo engines. A plug's gap widens as it wears, and a wider gap takes more voltage from the coil to fire. That extra load lands on the coil sitting right on top of the worn plug.
On a turbo CX-5 past 40,000 miles, the plugs come into the repair plan alongside the coil. Spark plugs are replaced as a full set, so all four go in together. On the non-turbo 2.0 and 2.5, we decide on plugs from the 75,000-mile mark and what we find at the misfiring cylinder. Since the coils already have to come off to reach the plugs, the new set goes in on the same visit.
What Goes Back on the Engine
Early CX-5s built before spring 2016 had coils that could fail internally, and a revised replacement coil is available for them. On those vehicles, the revised coil is the one that goes in. As each coil goes back onto its plug, a thin coat of dielectric grease goes inside the boot where it meets the plug porcelain. That grease seals out moisture at the spot where the spark leaves the coil. Once everything is back together, we run the engine and scan again to confirm the misfire code has cleared.
Book Your CX-5 Misfire Repair
Book a visit with Precision Auto Care in San Leandro at (510) 351-8211. We find the cause of the misfire and repair the part that failed. When you call, describe the shake and tell us if the light was flashing.
