Q: Car is randomly misfiring

asked by on October 17, 2016

i have random misfire only happens occationally for a split second accompanied with a ignition light flash momentarily otherwise the car runs perfect

My car has 106000 miles.
My car has a manual transmission.

There are a number of things that may cause this such as a faulty or dirty mass air flow sensor, a potentially a bad idle air control valve, or dirty fuel injectors. The mass air flow sensor is a unit in the intake system that monitors air intake as it is mixed with fuel prior to being injected into the motor. When this fails, this can cause an imbalanced air/fuel load to be supplied to the motor which often times results in the engine starving for air or fuel. This is what causes the hesitation or loss of power you describe. This can also cause the engine to struggle to idle for the same reason.

The idle air control valve is located on or near your intake manifold that monitors the air intake as it is mixed with fuel prior to being injected into the engine. This valve is controlled by the vehicle’s computer which will adjust idle speed based upon other measurements such as engine temperature, intake air temperature and electrical system load, or voltage.

When you accelerate, the engine RPM increases, and as you let off the gas, the RPM slowly returns to the normal idling speed. However, when the engine RPM drops below the normal range of 800 RPM (for most cars), it is more than likely that you are dealing with an IAC valve problem. In cases where this valve is clogged or is failing, your vehicle will stall instead of slowing to an idle after the release of the throttle.

If you need some assistance, I would recommend having an expert from YourMechanic come to your home to properly diagnose the misfire you have described for an accurate repair.

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