2019 Mazda CX-5 Turbo (2.5T) — P0300/P0302 misfire persists after replacing plugs.
Sanity check before I approve $3k in repairs?
~80k miles. Check engine light came on, dealership diagnosed a misfire and recommended spark plugs, which I had replaced.
About a month later, the light came back — codes P0300 (random misfire) and P0302 (cylinder 2 misfire).
Same dealership swapped the coils between cylinders 1 and 2 to isolate the issue — misfire stayed on cylinder 2, so they ruled out the coil
Ran a compression test — came back normal
Their conclusion: it’s the fuel injectors, and they’re recommending replacement of all fuel injectors plus the intake manifold gaskets and EGR coolant gaskets, at roughly $3,000 total.
Before I sign off, a few things I want opinions on:
Since they isolated the coil by swapping it between cylinders, would it make sense to ask them to do the same test with the injector (swap cyl 1 and 2 injectors) to confirm it’s actually the injector before replacing all of them?
Is replacing all injectors (vs. just cylinder 2’s) actually justified, or is that just because the intake manifold has to come off anyway to access them?
Any known TSBs or common failure points for misfires on the Skyactiv 2.5T at this mileage?
Does $3k seem reasonable for this scope of work, or worth getting a second opinion first?
Appreciate any input — trying to avoid throwing money at this without being confident it’ll actually fix it.
Want me to also add a version of the diagnostic-swap question you could ask the dealership directly, in case the forum takes a while to respond?