Why Won’t My Car Accelerate When I Push on The Gas?

Air Flow Problems

The most common cause of poor engine airflow is a clogged or damaged air filter. The air filter in your car protects the engine by catching all kinds of debris before it can enter the cylinder and cause more damage.

You can check your air filter yourself by opening the airbox, either by unsnapping a few clips or using a screwdriver, and removing the air filter. Do a visual inspection to see if the filter is full of debris on the intake side and try tapping it on the ground to see if you can dislodge some of the dust, dirt, and other items that accumulate over time.

If the filter is dirty, consider replacing it with a new air filter, since they are inexpensive, easy to replace, and can improve the performance and fuel economy of your vehicle.

Fuel Problems

Air flow problems tend to be fairly simple, but fuel delivery problems can be caused by a few different part failures, so here are the main offenders, starting at the fuel tank:

• Failing fuel pump. If your fuel pump fails to send the correct amount of fuel to the engine, then you can experience sluggish performance.
• A clogged fuel filter will restrict the flow and impact acceleration.
• Finally, your fuel injectors are the last point before the fuel enters the combustion chamber and if they are clogged, you’ll want to clean them.

Ignition Problems

The ignition system provides the spark in the cylinder to ignite the fuel-air mixture, but there are several possible failure points in that system, as well:

• Worn out spark plugs. Modern plugs can last a long time, with some service intervals in the 100,000-mile range. They do eventually wear out and become less efficient, so it’s important to replace them at your manufacturer’s recommended interval.
• Your spark plug wires can wear out or become damaged, causing loss of efficiency.
• Depending on the style of your vehicle ignition system, you may also run into problems with bad ignition coils, distributors, or ignition control modules.

Transmission Problems

If you notice that your engine is revving well, but the wheels aren’t turning in relation to the revs, you may have a transmission issue. In an automatic transmission, this would probably be the result of a bad torque converter or perhaps some internal transmission damage. In a manual transmission, it could be the result of a worn clutch.

TPS or Other Sensor Problems

The throttle position sensor (TPS) monitors the position of your throttle and communicates with the engine control module (ECM) to determine the best combination of fuel, air, and spark for the engine. A bad TPS will manifest itself in the following symptoms:

• Poor Acceleration
• Lack of Power
• Uneven Idle
• Check Engine Light

If you have a combination of these symptoms, it’s possible that you need to replace your TPS. Troubleshoot by using a code reader to access your vehicle OBDII port and read any fault codes. It will indicate whether the TPS is at fault. A code reader can also help to determine whether other important engine sensors, like the mass air-flow sensor, or oxygen sensor are faulty and need either cleaning or replacement.

Engine Compression Problems

An engine cylinder needs a tight seal in order to harness the explosive power of combustion. If the seal begins to fail, you can develop low compression and that will reduce your engine power, especially if more than one cylinder is experiencing those issues. Low compression can be a symptom of a few different mechanical problems:

• The engine head gasket keeps the coolant from entering the cylinder. A failed head gasket will allow gasses to escape from the cylinder and coolant to enter the cylinder. A slightly sweet-smelling exhaust can be an indicator that you have a head gasket leak.

• Your valves allow the fuel and air to enter the cylinder before combustion and exit the cylinder as exhaust after combustion. If they are damaged it can impact engine compression.

• Piston rings are fitted to the outside edge of the piston, and they maintain a seal between the piston and the cylinder wall. If they are worn or damaged, you may experience low compression as the pressure of combustion will escape past the rings into the crankcase. Damage to the piston or cylinder wall can also cause this symptom.

Engine Exhaust Problems

If your exhaust system is restricted in some way, the exhaust from the cylinders won’t flow freely and can cause the engine to lose power because the exhaust is pushing back into the cylinder.

Restrictions in the exhaust can come from a pinched exhaust pipe somewhere in the system, a collapsed muffler, or a clogged or collapsed catalytic converter.

Where to Start?

When troubleshooting, always start with the easiest possible fix, and progress to the more challenging repairs. For an acceleration problem, use some variation of this troubleshooting progression:

• Check to see if your parking brake is engaged or if something is stuffed under the gas pedal. It seems very obvious, but we’ve all been there.
• Use a code reader to check for faults. If your car has any fault codes active, then address them.
• Check your air filter, smell the exhaust for signs of head gasket failure, and listen for the loud whining of a failing fuel filter.
• Use a compression tester to test every cylinder.
• Do a visual test of the exhaust system.

If you’ve completed all these checks and still can’t determine the cause of your acceleration issues, take your vehicle to a qualified technician to help with the diagnoses. Let us help you find a repair shop, with professional mechanics to help you sort everything out.