Q: Car struggles to start, idles very low after startup.

asked by on November 06, 2017

Hey there!

My 2006 Mini cooper sport will struggle to start occasionally when I turn the key. The engine always rolls over fine, but sometimes I have to give it a little gas to get it to fully fire and start. After starting, it often idles very low and sputters but then corrects to stay running. Occasionally it will idle so low directly after starting that it will immediately die. Most of the time, after running a few minutes of idling, it stabilizes. It drives pretty much normal on the freeway and at higher speeds without a noticeable lack of power. When stopped though, and shifting from park to neutral to drive or any combo therein, it will drop in power and stutter and then self correct to stay running.

My main concern is why it struggles to start and needs me to give it gas oftentimes to assist in the engine fully starting.

The battery and alternator were replaced and checked last month and are unlikely the issue.

Thank you so much for your professional advice!

My car has 99900 miles.
My car has an automatic transmission.

This may be a sign of a faulty MAP sensor as the vehicle responds adversely to a load put on the motor (i.e. putting it in gear, making turns (which makes use of the power steering pressure switch) turning on AC or engaging the brakes). The Manifold Absolute Pressure (MAP) sensor senses engine load and generates a signal that is proportional to the amount of vacuum in the intake manifold. The engine computer then uses this information to adjust ignition timing and fuel enrichment. When the engine is working hard, intake vacuum drops as the throttle opens wide. The engine takes in more air, which requires more fuel to keep the air/fuel ratio in balance. When the computer reads a heavy load signal from the MAP sensor, it adjusts the fuel mixture to slightly more rich than normal so the engine can produce more power. The computer will then retard (back off) ignition timing slightly to prevent detonation that can damage the engine and decrease performance. This may also be caused by other closely related components such as a dirty or failing mass air-flow sensor, a faulty throttle position sensor or potentially a vacuum leak. I would recommend having an expert from YourMechanic come to your location to diagnose and inspect your vehicle.

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