Mazda CX-9 misfire problems

Filed Nov 4, 2026 · Engine · 86,000 miles · NJ

The contact owns a 2021 Mazda CX-9. The contact stated that while driving approximately 20 - 25 MPH, the check engine warning light illuminated. The contact used a diagnostic scanner and retrieved DTC: P0303, for a cylinder #3 misfire. The vehicle was taken to a local Mazda dealer to be diagnosed and repaired. The dealer found a coolant leak and performed a system cleaning and replaced the spark plugs and fuel injectors. However, the failure reoccurred. While the contact's wife was driving the vehicle, the check engine warning light illuminated, and the vehicle was towed to the dealer by the insurance company. The contact requested that the dealer inspect the cylinder head gasket and coolant system in his presence. The dealer informed the contact that the repair warranty would be limited to one year or 12,000 miles. The contact also contacted the manufacturer customer service but was not provided any additional assistance. The failure mileage was approximately 86,000.

Filed Oct 31, 2026 · Engine · FL

**the federal safety agency VEHICLE SAFETY COMPLAINT – ENGINE FAILURE AND UNAVAILABLE REPLACEMENT PART** I am filing this complaint regarding serious engine problems with my 2016 Mazda CX-9 equipped with the 2.5L SKYACTIV-G Turbo engine. My vehicle experienced significant engine problems, including overheating, diagnostic trouble codes P0014 (exhaust camshaft timing/VVT system performance) and P0303 (cylinder 3 misfire). Following diagnosis, the cylinder head was found to be cracked, requiring machining and replacement of the timing kit. Despite these extensive repairs and expenses, the vehicle continues to have unresolved engine problems, including rough idling. The vehicle has not been fully repaired because I cannot obtain the exhaust-side Variable Valve Timing (VVT) actuator required to complete the repair. I have been unable to locate this component, and Mazda USA has indicated that the part is not available through its U.S. or Canadian parts network. This leaves me with a vehicle that cannot be properly repaired due to the apparent unavailability of a critical engine component. I find it unacceptable that an essential engine component for a Mazda vehicle cannot be sourced through the manufacturer or its authorized parts network. The situation has resulted in significant financial hardship, prolonged vehicle downtime, and the inability to restore my vehicle to proper operating condition. I am concerned that the underlying engine and VVT-related problems may represent a broader safety and reliability issue affecting other owners of 2016 Mazda CX-9 vehicles equipped with the 2.5L turbocharged engine. I respectfully request that the federal safety agency investigate the reported engine problems, including overheating, cylinder-head cracking, VVT actuator failures, and the availability of replacement components. I also ask that the federal safety agency determine whether these conditions represent a safety defect that warrants further investigation or corrective action by Mazda.

Filed Jul 23, 2026 · Engine · RI

1) What component or system failed or malfunctioned: On 6/12/2026 While drive on the highway with our daughter in the car and we experienced a high speed stall. The engine failed and we lost power. We barely got the car of the highway and coasted into a parking lot. 2) Life threating for Father, Mother and daughter and other drivers on the highway. 3) The Mazda dealer stated they were unable to reproduced problem. The diagnostic report showed few random misfired on two cylinders 2 & 3. Autozone detected codes P0300 with Secondary DTCs U0442-00 4) There car was only inspected by the dealer. The vehicle has not been inspected by Mazda the manufacturer. We requested Mazda to escalate this to the District Service Manger and to open hotline call with Mazda corporate but both of these were denied. All our service has been performed at Mazda dealer, including oil changes. We have always received a video of them working on our car with a detailed summary of what done. We did not receive the video or diagnostic report for this issue. 5) There were no warning lamps, no messages or other symptoms of the problem prior to the failure.

Filed Jun 1, 2026 · Fuel system · AL

Prior to [XXX] The vehicle ran rough and sputter excessively. I took car to local repair shop. Diagnostic equipment determined the fuel injector needed to be replaced. Vehicle ran better but continued to sputter and ride rough on occasion. Prior to [XXX], the vehicle stopped operating properly. The vehicle would not travel faster than 20 mph and sometimes would stop completely in the middle of the road. This was a hazardous situation. The vehicle seemed to be starved for fuel. All warning lights were displayed on the short trip home. Being too dangerous to drive the vehicle was towed to a different repair shop. Diagnostic equipment determined the throttle body needed to be replaced. This was done prior to [XXX]. I drove the car less than 5 miles after the 2nd repair and the same behavior returned. Vehicle would sputter run rough sometimes stop etc. All warning lights were displayed. Vehicle seemed to be starved for fuel. Vehicle was towed back to the repair shop. Next step will be to contact Mazda dealership in Huntsville AL and see if they will accept the Vehicle for repairs after I have it towed. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Sep 9, 2025 · Brakes, Electrical · PA

my 2018 MAZDA CX-9 safety issue SCBS / SBS, LAS / LDWS, MASTER AND/OR HBC WARNING LIGHTS Forward sensing camera (FSC) stops functioning cause my car run rough even depress accelration and those light came on dashbaord -Forworad smart city brake support malfunction -smart brake system -front camera sensor malfunction

Filed Oct 20, 2024 · Engine · AZ

I purchased a 2018 Mazda cx9 from a local used car dealer several weeks ago. Check engine light came on after a few weeks for cylinder 3 misfire and there was a steep decline of the vehicle performance (hard start, rough idle, lower mpg, sluggish driving). Took it to Berge Mazda who charged me for diagnostics/spark plugs, and ignition coil. They informed me the next steps were a compression tests, fuel injectors and if that didn’t fix the problem then they wanted to strip down the engine to evaluate the cylinder head. At this point I decided to take it to my local mechanic who I trust, he diagnosed a cracked cylinder head. Now I’m stuck with a car I just bought that’s unsafe to drive needing a 6-8k repair. Upon further research there is a widespread problem with Mazda’s manufacturing of there cylinder heads on certain models (including the 2018 Mazda cx9). This is confirmed by TSB’s from Mazda along with a class action lawsuit recently filed. Upon more research on my vehicles history, I gathered that my vehicle was traded into Horne Mazda and then a couple days later auctioned to the used car dealer I bought it from. The fact that Mazda is selling off their own defective vehicles that are unsafe at auctions is absolutely disgusting and something needs to be done about it.

Filed Aug 14, 2024 · Engine, Fuel system · MD

We have a 2015 Mazda CX-9 Touring with All-Wheel Drive (AWD). The issue that has been happening is a flashing check engine light (CEL) indicator showing up in the gauge cluster. This issue originally started in October of 2023. I was on the highway doing at least 55 miles per hour (mph). Before the light actually came on, I had already felt the vehicle shaking, and also noticed the acceleration was sluggish. In the blink of an eye, the CEL came on and started flashing. After that point, the CEL stayed on. I was able to get to my destination safely. We took the vehicle to a shop, and told the mechanics the issue, but they could not re-create what happened. We stopped driving the vehicle as much after this first encounter. A couple of months later, the issue still persisted, and we took it to another shop. They changed the spark plugs, and the vehicle had been driving CEL-free for several months. Recently, we were going to take the vehicle out for a drive, and noticed the vehicle shaking (before the CEL officially came on) again. The CEL flashed and came on. As of this moment, the CEL pops up and stays on when starting the vehicle. I put in a code reader, and the code that came up was “PO304 Cylinder 4 Misfire Detected.” We are figuring out what our next plan(s) is/are with the vehicle. I looked at some forums for the 2007-2015 Mazda CX-9 Generation, and I noticed that someone mentioned that there was an issue with the injector pigtail wire (one of the fuel injectors). They also mentioned spark plugs and coil plugs. But they still had an issue and it seemed to be not resolved. I'm wondering if this issue could have a direct or indirect connection with the Takata Airbag recall that was issued on August 13th, 2024 with a "Do Not Drive" alert.

Filed Jun 12, 2024 · Brakes · CT

While driving the vehicle the brakes became hard to depress and a hissing came from my steering column, the car would not stop or respond to stop. I had to downshift to Neutral to get the speed slow enough to stop - and had passed through an intersection while in failure. I had also had symptoms I did not know at the time may be related which was at a stop at dunkins or a drive through at a stopped position - where the car would run rough the last few weeks. I thought the rough idle was gas related. I can no longer drive the vehicle and am told this is brake booster/pump issue / that other of the same parts in fords and other manufacturers are now extending customer sat programs like 13N02 because of faulty parts in the brake booster. the vehicle can be towed or seen for this problem. The vehicle has no existing coverage of the faulty brake booster. This is a car insured for my son [XXX][ to drive and It is a safety risk that this went while driving, i'm happy it was myself driving that day. Problem has been confirmed as a brake booster pump/booster failure by a service professional. No warning lights - just not able to stop the car when stepping on the brake. Thanks INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)

Filed Jun 6, 2024 · Engine · CA

Started with rough idle then got overheating msg on dashboard. After the diagnostics they found cracked cylinder head and quoted $6000 for replacement. Called Mazda USA and they denied our claim. Car is under 5yrs old & around 74k. While working on the car they noticed the turbo needed it to be rebuilt. Another $2k. There is TSB out for this and it’s a known problem, lot of others having/had same issues. Never had a car that needed an engine replacement even before car is paid off.

Filed Jun 27, 2022 · Engine · FL

Car starting misfiring . I was told it appears to have a crack in the head gasket & would be best to repair the engine . This car has only 80k miles and should NOT be doing this at this stage!!!