2019 mazda cx-5: Need new fuel injectors?

I originally had what I thought smart brake and air intake issues.

The Mazda tech originally thought it was dislodged air intake module that led to overheating of sensors.

When I drove the car back home, the car kept on hesitating as I pressed on the accelerator. Then gray smoke came out the exhaust. I brought the car back to Mazda and had the tech drive along with me to see. When he tried to accelerate, the same thing happened (hesitation, smoke).

They did another diagnostic check and he said that the air/fuel mixture is off - too much fuel, not enough air.

They told me that I need to replace the fuel injectors.

I never heard of a 2 year old car needing new fuel injectors. Can a 2 year old car with about 6K miles need new fuel injectors?

That would be very unusual. They’re repairing it under warranty, right?

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Stranger things have happened… so sure, an injector can fail at 6k miles. Likely one stuck open and the warranty procedure is to replace the set.

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Some years back my youngest son bought a near new 2013 Camaro with 6k miles on it.
At about 10k miles a performance problem developed.

It turned out that one injector had failed. Warranty covered it and to GM’s credit they replaced all of them.
So while unusual, it can and does happen.


You don’t have much choice here, do you? I’d tell the shop that you are pretty unhappy with their work so far, but you’ll only be happy when they are sure it’s fixed, so they should lend you a similar car and keep yours until it’s fixed. If they can’t fix it you want a replacement car. To goal is to get it fixed without it being your job to test drive it every time they try something.

A shop would usually do a few tests before thinking the injectors were the problem.

  • fuel pressure test, including testing the vacuum input to the fuel pressure regulator
  • injector balance test. Turn on the fuel pump until the pressure is correct, turn it off, pulse the injector a fixed number of times, then measure how much the fuel-rail pressure drops. It should drop the same, correct amount for all the injectors.

Have those two tests been performed?

If the technician needs these tips, he is in trouble.

The fuel pressure is monitored by the PCM, it is always being tested.
The high pressure fuel supply is controlled electronically, vacuum diaphragms went away years ago.

Fuel pumps to the injectors are mechanical these days, electric pumps can’t generate enough pressure for a direct injection system.

My point is it shouldn’t require that a car owner learn auto mechanics to get proper service from a dealer. This person clearly has a car with a problem and it’s their responsibility to fix it. Period. When they do they can return her car but in the meantime they must loan her another comparable car.