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Q: Just bought ran good 100 km now stalls at Red lights

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Just bought filled tank with gas ran city errands 55km dropped one kid off and headed to hi way 50km round trip ran great parked her had super and ran an errand now at Red lights would sputter step on gas and either go or sputter on way home leaving red lights would stall and rattle if gave gas so stall at 4 red lights and needed to be floored to restart. Once going was good . In Driveway at 1000rpms give gas loose rpms feather it slightly raise to 1500 same lost rpms if give gas hit peddle twice if you will it stalled once rpms up seems ok

My car has 244000 miles.
My car has an automatic transmission.

A: This may be a sign of a failing mass air fl...

This may be a sign of a failing mass air flow sensor, a failing idle air control valve or potentially a clogged catalytic converter. As you may already know, the catalytic converter converts toxic exhaust gases into less harmful pollutants that are suitable to be expelled into the atmosphere. When this is clogged, this causes these gases to be backed up into the exhaust system not allowing the engine to breathe properly (think of a backed up sink). When this happens, the engine I forced to work much harder to expel these gases. This often results in the engine bogging down and causing very poor fuel economy. This should also cause a check engine light to come on as the O2 sensors should be reading the incorrect amounts of oxygen in the exhaust gases if this is your problem.

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.

This may also be a sign of a failing idle air control valve. 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 nearing its replacement age, your vehicle will stall instead of idling after the release of the throttle.

If you’d like to get this fixed, I would suggest having a professional from YourMechanic come to your home to diagnose and identify the cause of your stalling issue.

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