Hi everyone,
I drive a 2017 Mazda 3 1.5L engine with 125,000 km on it. The car is regularly maintained — oil changes every 10,000 km, and spark plugs were replaced at 100,000 km to OEM plugs.
For the past 6 months or so, I’ve been dealing with a low-level misfire across all cylinders. It’s intermittent and hard to reproduce consistently, but I’ve noticed it tends to happen more often during long drives in heavy traffic. The fuel I use is 95 octane, which is the minimum available in my country. I’ve tried a few high-end fuel additives, but they haven’t helped.
Additional symptoms:
* Short 2-second shake when accelerating from a stoplight (just started recently, happened ones).
* Slight RPM fluctuations while cruising at low speeds.
* Occasional “squeezing” noise right before/after shifting gears, only when pushing the gas paddle hard or under hard driving.
* Fuel trims seem normal (usually within ±5%).
* Car drives fine at highway speeds — the issues mostly show up at low speeds or during acceleration.
* No check engine light or codes.
I’m thinking about cleaning the MAF sensor and throttle body next. Does this sound like a fuel delivery issue, sensor problem, or something else? Any specific areas I should check next (e.g., coil packs, motor mounts, transmission components, etc.)?
Appreciate any input or experience with similar issues!
Sounds to me like it could be due to carbon buildup, especially on the intake valves. This is common on these kinds of direct injection only engines, such as the Mazda Skyaktiv G. If this would be the case, then the best fix would be to get walnut shell blasting of the valves done.
Check live data for problems.
Strange noise:
I also noticed a squeaking/squealing noise that usually happened when driving hard and shifting gears- I managed to recreate it today while the car was parked- if I rev the engine to ~3000 RPM and turn the AC on or off, the squeak happens every time the AC compressor kicks in.
I'm thinking of cleaning the MAF sensor and throttle body next, but I'm also wondering if the AC compressor, serpentine belt, or belt tensioner might be related to the noise and possibly causing extra load that affects drivability.
Questions:
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Could the AC system or belt-related components be contributing to the misfire or RPM fluctuation?
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Is it worth checking coil packs or motor mounts?
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Any common issues in this model that could cause these symptoms?
Appreciate any insights or suggestions before I start throwing parts at it.
Thanks in advance!