It's in the subject line ... P0302 with 26,720 miles
I missed it.
My thought process on this is with a life of short trips on surface streets, the skyactiv 2.5T in the OP's signature trim cx5 is spending much more time at an enriched "warm up" mixture than a car driven typically longer distances at a time and highway use. Additionally, with lower speeds on surface streets, that lower 26720mi on the odometer could be equivalent engine time running of a typical CX5 at double the mileage. If I recall, the turbo engine is recommended to have spark plugs replaced at 40k miles?
It's true, but how often do you see CX-5's with misfire codes on this site? When you do, they are usually at over 100k miles. At 26 miles, assuming it's not some temporary glitch that goes away, it is unusual regardless of the way it's been driven.
So, to me, (IMHO) it stands to reason that a vehicle driven in such an environment as I had asked about
could be ready for some new spark plugs. It's
possible that the motor
could possibly have some carbon buildup issues from that type of operating environment.
@Lazy2.5 , what's the reasoning for your position of "still shouldn't" ?
I do have the NA 2.5. Spark plugs have always been changed at or before the suggested interval. As I have mentioned before, the only time I ever got a misfire code was due to defective (almost new) spark plugs. My car saw lots of city driving when it was newer.
If it were my car, I'd wait to see if the code came back.
Yes, do that, OP.
If so, I would give it an "Italian tuneup" with a nice couple of hours drive in the country with some heavy throttle and higher rpms. If that didn't help I'd go new spark plugs. That would be my progression before going to a mechanic or dealer.
For optimal engine and catalytic converter health, a
solid 30-minute drive at highway speeds (e.g., 50-60 MPH in 6th gear) with a light throttle is highly recommended, ideally once a week or more. This duration is sufficient to ensure the engine oil reaches its optimal operating temperature, effectively burning off contaminants and excess fuel that may have accumulated in the crankcase, and allowing the PCV system to function at its peak. This sustained, moderate operation also keeps the catalytic converter within its optimal temperature range (400-650°C), efficiently oxidizing accumulated carbon deposits on its surface.
Driving for "a couple of hours" solely for the sake of an 'Italian tune-up' is unnecessary and makes no sense, as the primary benefits are achieved much quicker.
During my vehicle's tuning process, datalogs revealed that the stock Air-Fuel Ratios (AFRs) would drop to a very rich 10.5-11:1 during sustained Wide Open Throttle (WOT). Even after tuning, the target value of 12.5:1 AFR is still rich compared to stoichiometric. This rich mixture, commanded by the ECU to cool and protect the engine and catalytic converter under extreme load,
will not burn off deposits. Instead, the combustion of excess fuel in the exhaust manifold and converter will lead to dangerously high catalytic converter temperatures.
Therefore, for truly removing engine and catalytic converter deposits, the best way is through regular, sustained driving that brings the engine and exhaust components to their optimal operating temperatures for at least 20-30 minutes.
I want to clarify: If attempting the 'Italian tune-up' through more aggressive means, it should be limited to
1-2 consecutive acceleration runs, not exceeding 5000 RPM, and in a gear no higher than 3rd. Pushing beyond these parameters, such as higher RPMs or in higher gears for sustained WOT, triggers very rich AFRs (Especially in your turbocharged engine) to protect the engine and catalytic converter from extreme heat. This richness, while protective for the engine, makes the process
totally redundant for burning off deposits in the catalytic converter, and paradoxically,
contributes to additional deposits as well as
obscene cat converter temperatures. (over 900c observed while logging data with Mazdaedit)
The focus should be on consistent, moderate-load driving to maintain engine and emissions system health, rather than relying on extreme, short-duration events that induce damaging heat.
