I just got back from a road trip, and now my car is vibrating at idle. A few days ago, the check engine light came on. I scanned it and got a P0303 code for a cylinder 3 misfire.
I replaced the spark plugs and moved the coil packs around, but it’s still misfiring. I scheduled an appointment with the dealership for warranty repairs.
I’ve never brought a car in for warranty work, so I’m nervous they might deny the repair. My CX-50 has a Corksport air intake that’s been installed since the first month I got the car and has run fine for 30K miles.
Could they deny my warranty claim because of the intake? I know it can’t cause a misfire, but I’ve heard stories of people getting repairs denied over minor things. For example, someone had an engine replacement denied because they changed their oil every 5,600 miles instead of 5,000.
I do my own oil changes every 5K miles, but I worry they might use that against me too. I have all the original intake parts. Should I put the stock intake back on before bringing it in, or should I just leave it?
I love this car, but I’m disappointed to be dealing with this problem so soon. My other car, a 2016 MX-5, has over 140K miles with zero dealer visits and only self-maintenance. I expected more from the CX-50.
This issue is becoming more common. I have one in my shop with the same P0303 code. Cylinder 3 had a 100% leak during a test, and Mazda approved a cylinder head replacement. The intake shouldn’t cause a problem, but it’s safer to reinstall the stock one. It really depends on how the dealership presents it to Mazda.
@Caden
Exactly. The intake isn’t causing the misfire, but swapping back to the stock setup before going to the dealer is the safest move with how warranty repairs work.
Sam said:
Just take it off. It’ll save you from giving them any reason to deny your claim.
It’ll take more than a few seconds to put the stock setup back on, but you’re right. I have some free time tomorrow, so I’ll do it. Glad I kept all the original parts.
Sam said: @Merlin
Are you swapping the entire intake or just the short ram? I recently swapped the short ram in a few minutes when I took our CX-30 in.
The whole intake, including the turbo inlet and heat shield.
It depends on the dealer. If a car came into my shop with a misfire and just an intake mod, I wouldn’t mention it since it doesn’t cause misfires. You should have done a compression test before replacing the spark plugs, though. I had a 2023 CX-5 Turbo last summer with 40K miles that suddenly lost compression in cylinder 1, and Mazda covered the engine replacement. I hope yours is something simpler like a fuel injector.
Merlin said: @Arlen
If you’re in Illinois, I’d happily bring my car to you!
I wish! I’m in Tennessee, but I hope it gets sorted out for you. At least in Illinois, Mazda pays techs more for engine swaps due to state laws, unlike here where we get paid less time for the same job.
@Arlen
I’m starting to think it could be an injector. I used my tuning tablet from my MX-5 to check live data, and the injector pulse width showed 1.5ms but would randomly drop to 0.0ms. I couldn’t check each injector individually, but maybe if I record the data, I can analyze it later. I wish I had a compression tester.
Did you tune the car after adding the intake? Some cars run lean with a new intake on the stock tune. I’d still remove the intake to make the warranty process easier.
Bowie said:
Did you tune the car after adding the intake? Some cars run lean with a new intake on the stock tune. I’d still remove the intake to make the warranty process easier.
If the intake was causing it to run lean, it would’ve failed long before 30K miles. Temps and AFRs are normal. I’ll probably reinstall the stock intake, but I’m confident it’s not the problem.