Corvette: Why is My Car Misfiring?

This article outlines the causes and solutions of engine misfire.

By James Karuga - February 25, 2015

This article applies to the C5, C6 and C7 Corvette (1997-current).

Tracking down the issue of why your C5, C6 or C7 engine is misfiring is not easy. That's because a misfiring engine can be caused by many mechanical problems. One way to detect a misfiring engine is by sensing the Corvette's engine stumbling momentarily before regaining power. The engine can jerk or run rough as a result. This happens because the engine has skipped a process in the combustion cycle. A misfiring engine results in lowered gas mileage and engine power. This article will help you trace the possible sources and solutions to your engine misfire woes.

Figure 1. On board computer showing trouble codes.

Step 1 – Check the spark plugs

If your Corvette's spark plugs are damaged, the engine will misfire. That happens because the cylinders fail to properly fire, since damaged plugs don't provide an electric spark that ignites the air/fuel mixture in the engine. The explosion the spark plugs create moves the cylinder down, and the force produced is transferred to your Corvette's wheels for motion.

If spark plugs are blown, worn out or loose, your Corvette will misfire. If loose, adjust them back and the misfiring will cease. if damaged, replace them. After every 10,000 miles, motoring experts advise that the spark plugs need to be supervised as they can stop functioning. They may last up to 50,000 miles, but the risk is they could fail without warning. Faulty plugs also cause an engine misfire while the Corvette is decelerating according to some Corvette owners' experiences.

Figure 2. Reading spark plugs.

Pro Tip

When spark plug wires are being replaced, proper routing is vital to avoid them coming into contact with the exhaust manifold. Also, they should be checked thoroughly to ensure every insulation is in place. This is because if they contact the exhaust manifold, engine misfires happen.

Step 2 – Check the ignition coils

The ignition coils step up the 12 volt battery charge to high voltage direct current around 50,000 volts or higher, which fires up the spark plugs. As such they are high voltage transformers. However, if your Corvette's ignition coils are damaged, no spark will ignite the air/fuel mixture, and as a result, the engine will misfire or not start, especially when the Corvette is loaded.

Damaged ignition coils can cause damage to the engine or catalytic converter as well. Ignition coils are prone to damage from voltage overload, caused by faulty spark plugs. You can detect damaged coils if the Corvette's engine runs rough. When replacing ignition coils, motoring experts advise for the cleaning of connectors and checking for corrosion or looseness on them. This ensures electrical transmission is not hampered.

Figure 3. Corvette coil packs.

Step 3 – Check fuel injectors

Fuel injectors are supposed to regulate and deliver the right amount of fuel at the right moment to the engine. But, if your Corvette's fuel injector is faulty, the engine will misfire. One way to detect a problem with the Corvette's fuel injector is if you smell fuel (leaks), the engine cranks but fails to start, and has low power. Fuel injectors are susceptible to clogging by dirt, and such an issue is solved by cleaning them. Alternatively, for about $15 per injector, there are services that will bench test and service your injectors to optimize flow and detect any issues.

According to motoring experts, if your fuel injector fails to buzz like your engine, it's "dead." Also, if your Corvette has random misfires that can't be traced to any cylinder, it could be the case that the injectors are dirty and require cleaning.

Figure 4. Fuel injectors.

Step 4 – Low voltage battery

If Your Corvette's battery is faulty or has low voltage, the engine will suffer from a lean misfire. A low voltage battery affects fuel delivery since the fuel pump runs slower than expected. As a result, the fuel pressure is low and a lean fuel condition occurs. In other instances, a low battery hampers the normal opening of fuel injectors, resulting in lean misfire or a hard start. To test your battery, use a volt meter and touch the prongs to the positive and negative terminals. Anything over 12.6V is a well-charged battery, and if the voltage is near 12.0V, the battery needs to be replaced.

Figure 5. A well-charged battery.

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