Understanding Engine Misfires

Misfire Repair 

European cars like Audi, BMW, Land Rover and Volkswagen are engineered to allow for performance and comfort. Unfortunately, in the service of creating performance these engines tend to misfire if they are not properly maintained. Below we’ll discuss some of the symptoms of a misfiring engine as well as testing methods for the problem.

Common Symptoms of a Misfire

The first sign of misfiring issues in your Audi or BMW might be rough idling and slower than normal acceleration. The sound of your engine revving up might also change. One rather obvious sign of an engine problem or misfiring involves the “Check Engine” light or the “Service Engine Soon” light showing up on your dashboard.

Another common sign is the dreaded P300 family of codes which may indicate a random misfire or a cylinder specific misfire.

Keep in mind that misfire is your vehicle’s way of telling you that there’s a fault within the cylinder that must be addressed and will not resolve itself.

Why do European cars misfire sometimes?

Engine misfires are the result of either an ignition, fuel or mechanical fault. Mechanical faults are verified by the compression within the cylinder. Ignition misfires may be due to a spark plug that is no longer able to generate the spark required to jump the gap with the correct amount of power and at the right time. Faulty ignition coils and/or wiring may also lead to ignition related misfires.


The third cause of a misfire is fuel related. In cylinder, the idle ratio of air to fuel is 14.7 grams of air for every gram of fuel. The ratio allows for proper combustion provided that the spark is on time and has the proper power.


Running Rich vs Running Lean


The power of an engine is managed by the passage of air through the system. When a vehicle is running lean the cylinder or cylinders have more air than fuel. The vehicle will then set off the check engine or service engine soon as well as a P300 or P300 cylinder specific code. Conversely if an engine is running rich the ratio of air to fuel indicates that there is more fuel than air required for proper combustion.


If a vehicle is running rich, this means that raw fuel may be entering the catalytic converter and will damage the catalytic converter which can be a costly repair. If the vehicle is running lean the engine will have drivability concerns and will eventually stall out.


The takeaway is that the first step in the service or repair of an engine with a misfire is to establish if the misfire is due to a mechanical, fuel or ignition fault and keep in mind that it may be a combination or all three!


At Green’s Garage we find the root of your problem, and our trusted mechanics will inform you about what you can do to keep your vehicle running smoothly.

Misfire testing procedures

Without getting overly technical, testing for a misfire requires testing all the systems that could cause a misfire, starting with the ignition system, fuel system, mechanical and electrical.

For those customers who have a European vehicle please keep in mind that Turbo engines have a unique aspirating system and many also have gasoline direct injection (GDI). These systems require precise testing which may include live testing of the Short Term and Long-Term Fuel Trims, Lambda Readings and lab scoping oxygen sensors.


How can I avoid misfires?

The easiest way is to have your vehicle inspected and to ensure that mechanical, ignition and mechanical systems are functioning properly. Typical service may include the cleaning of fuel injectors, removing carbon build-up to allow for valves to seat properly and ensure proper aspiration of the engine, and replacing spark plugs per the manufacturer.

Ideally, having routine maintenance for your European vehicle will prevent future misfires and keep your vehicle performing as it should. Green’s Garage specializes in these makes of vehicle, from European to American made, and can ensure that your vehicle is up to date with what the manufacturer recommends and more.


Engine misfire diagnosis and repair in Miami

Since 1957 Green’s Garage has served the Miami and South Florida community. We don’t engage in guess work; all of our services and repairs are based on data. We provide all of our customers with before and after photos and freeze frame data of your vehicle’s engine. If you’re experiencing a misfire schedule service today and allow one of service professionals to service or repair your engine.

All of our work comes with a nationwide warranty through Technet valid for 2 years or 24,000 miles.

Green's Garage is committed to ensuring effective communication and digital accessibility to all users. We are continually improving the user experience for everyone, and apply the relevant accessibility standards to achieve these goals. We welcome your feedback. Please call Green's Garage (305) 444-8881 if you have any issues in accessing any area of our website.