rapid acceration of the engine when stopping

ANSWER : What you are describing sounds like a dirty or failing idle air control valve. The idle air control valve monitors the air intake as it is mixed with fuel prior to being injected into the engine at low speeds and at idle. This valve is controlled by the vehicle’s computer and will adjust idle speed based upon other measurements such as engine temperature, intake air temperature and electrical system load or voltage. This is also an important function when starting the motor as it allows the motor to run and idle on it’s own once the motor fires. When you accelerate, the engine RPM increases, and as you let off the gas, the RPM slowly returns to the normal idling speed with the help of the idle air control valve making the transition from a higher RPM back down to idle speed while adjusting the air/fuel ratio constantly to allow this to happen smoothly. When the engine RPM drops below the normal range of about 800 RPM, this often times will cause the engine to stall indicating a dirty or faulty idle air control valve. I would recommend having an expert from YourMechanic come to your location to diagnose and inspect your vehicle.

ANSWER : Hi there. In both cases, when an AC system is not working and a warning light is coming on the dashboard, typically a professional mechanic will complete the same initial inspection, which is to download the stored error codes that triggered the warning light initially. This tends to give them an idea as to what is causing the problems. This could be something as simple as an electrical relay that is faulty or loose or an indication of a computer related "glitch". Either way, the best way to move forward is to have a professional mobile mechanic complete a check engine light inspection.

ANSWER : Anything is possible with enough engineering. The changes you are looking at would take major structural changes and would definitely not be an easy job. You could possibly consult a manufacturing engineer to get more details on how this could actually be carried out and whether it would be feasible.

ANSWER : Hello. Warning lights accompanied with stalling can be caused by many things. If the oil is low I would go ahead and top it off to prevent the possibility of engine damage, however, it is unlikely that low oil is what caused the stalling. Stalling is most commonly caused by issues with the ignition, engine management, or fuel systems. If one of the components, such as a major sensor, the fuel pump, or the ignition coil, go out or have an issue they can cause the engine to stall. If the vehicle is no longer starting then it may be possible that there is an issue with the electrical system as well, perhaps a faulty battery or alternator. If the alternator goes out it will eventually drain the battery, which could also cause stalling. Scanning the computer for trouble codes, once the vehicle is started, will likely reveal some insight into what the issue may be. As the possibilities could be many, I would recommend having a professional technician, such as one from YourMechanic, come to your location diagnose what may have caused your vehicle to stall.

ANSWER : Hi there. Most of the time, reduced engine power is caused by a restriction of fuel, or the throttle body’s inability to efficiently mix air and fuel. This could be caused by a failing mass air flow sensor, EGR valve or other fuel system components. Since the check engine light is on, you should have a professional mechanic complete an inspection at your location to determine what codes are stored and which components require repair. This should resolve your issue.

ANSWER : Hi there. Typically when you have a rapid RPM increase like you’ve described, it is caused by either a vacuum leak, a computer PCM-related glitch or an idle control valve that is stuck or damaged. It’s also possible that a component on the throttle body or electric throttle control is causing this problem as well. This is a potentially dangerous issue, which should be resolved sooner than later. I would recommend having a professional mechanic come to your location to complete a engine RPM is high inspection. This will allow them to pinpoint the source of this issue and let you know what needs to be done to fix the problem.

ANSWER : Hi there. There are a lot of things that can cause this on your 2012 BMW M5. I usually start by scanning the computer for codes to see what comes up. If there are not codes then I load test the alternator and the battery to see if they are failing. Low voltage in the electrical system will cause this. If that is fine, then it is usually caused by a failing throttle body. I have seen a lot of these fail due to the motors in them hanging up. If the problem is only happening intermittently, this can make the issue hard to duplicate, but you can still have tests done on the car. If you are going to have this fixed, consider YourMechanic, as a certified mechanic can come to your home or office to test the vehicle and diagnose the Engine Malfunction Light.

ANSWER : Hi There,
It sounds like you may have one of two possible issues. The issue of idling and stalling may be related to a dirty or faulty idle air control valve. The idle air control valve monitors the air intake as it is mixed with fuel prior to being injected into the engine at low speeds and at idle. This valve is controlled by the vehicle’s computer and will adjust idle speed based upon other measurements such as engine temperature, intake air temperature and electrical system load or voltage. This is also an important function when starting the motor as it allows the motor to run and idle on it’s own once the motor fires. When you accelerate, the engine RPM increases, and as you let off the gas, the RPM slowly returns to the normal idling speed with the help of the idle air control valve making the transition from a higher RPM back down to idle speed while adjusting the air/fuel ratio constantly to allow this to happen smoothly. When the engine RPM drops below the normal range of about ~800 RPM, this often times will cause the engine to stall indicating a dirty or faulty idle air control valve.

When the truck stalls at highway speed and does not immediately start right away after, this suggests you may have an ignition coil that may be starting to fail. Ignition coils are coated with a varnish-like insulation that becomes brittle over time after being stretched then contracted repeatedly The insulation develops small fractures that open when heated and close when cooled. When open, they allow shorting of coil windings and decrease or eliminate the coil’s ability to function. This type of temperature cycling happens because every time you shut the engine off, the fan stops running, the coolant stops flowing and the temperature under the hood rises. Every time you start the engine again the coolant flows, the fans turn on, and the temperature drops. When this heat dissipates and is absorbed under the hood, it is trapped causing this cycling effect. Components that contain heat sensitive materials include parts like coils, injectors, igniters, and some sensors. Any of these may be potentially subject to this same kind of heat problem which can be very difficult to trace. I would recommend having an expert from YourMechanic come to your location to take a look at your vehicle.