# Why does my car lose power when accelerating? **Verdict:** Drive to a shop this week - **Most common cause:** Misfire from worn spark plugs or a failing coil - **Urgency:** This week - **Typical fix:** $20-$2,500 - **Causes to check:** 5 ## Quick answer A car that loses power when accelerating most often has a misfire from worn spark plugs or a failing coil, a weak fuel pump or clogged filter, or a dirty mass airflow sensor. A clogged catalytic converter or a turbo boost leak are less common causes. Many of these set a check engine light, and the car may enter limp mode to protect itself. ## What is happening? An engine makes power by burning the right mix of air and fuel at the right moment in each cylinder, then pushing the exhaust out. Accelerating asks for the most of all three at once: more air, more fuel and a strong spark, with a clear path for exhaust. Losing power when accelerating means one of those can no longer keep up with demand, even if the engine feels fine at idle or a steady cruise. It matters because the causes tend to build on each other. An ignored misfire sends unburned fuel into the exhaust and can melt the catalytic converter, which turns a 200 dollar plug job into a 2,000 dollar repair. Many cars also enter limp mode when the computer sees a serious fault, cutting power and limiting gears to protect the engine or transmission. A car that cannot accelerate is also a hazard when merging onto a highway. ## What causes it? The 5 most likely reasons 1. **Misfire from worn spark plugs or a failing coil** (most common), $150-$600. When a cylinder does not fire properly, the engine loses part of its power, and the effect is strongest under load, such as climbing hills or merging. Worn plugs need more voltage to spark, which strains the coils until one fails. A misfire usually feels like stumbling or jerking and often sets a check engine light. How to confirm: The engine stumbles or shakes under hard acceleration, the check engine light is on or flashing, and a scan shows P0300 or a single-cylinder code. Fix: Replace the spark plugs or the failing ignition coil. 2. **Weak fuel pump or clogged fuel filter** (common), $150-$1,300. Under hard acceleration the engine needs the most fuel, so a pump that is wearing out or a clogged filter shows up there first. The car may feel fine at idle and gentle cruising, then sag, surge or buckle uphill and with a full load. Running the tank very low often can shorten pump life, and some pumps whine first. How to confirm: Power fades under heavy load or uphill but returns when you ease off. A shop can measure fuel pressure, and low pressure codes may be stored. Fix: Replace the fuel pump or fuel filter. 3. **Dirty or failing mass airflow sensor or clogged air filter** (common), $20-$450. The mass airflow sensor measures incoming air so the computer can add the right amount of fuel. Dirt or oil on its sensing wire makes it under-read, so the engine runs lean and feels flat. A very dirty air filter restricts airflow at high demand too. Lean codes or a MAF code commonly appear. How to confirm: Check the air filter for heavy dirt. A scan may show P0101, P0171 or P0174, and the engine often improves after the sensor is cleaned with MAF cleaner. Fix: Replace the air filter, clean or replace the MAF sensor. 4. **Clogged catalytic converter** (less common), $1,000-$2,500. The catalytic converter can melt or clog inside after long periods of misfiring, burning oil or running rich. That blocks the exhaust, so the engine cannot breathe out and power drops more the harder you push, sometimes with a rotten egg smell or red-hot converter. It is more likely on high-mileage engines with an earlier misfire problem. How to confirm: Power gets worse the longer you accelerate, the car struggles to reach highway speed, and a shop finds high exhaust back pressure or a rattling converter. Fix: Replace the catalytic converter (and fix what clogged it). 5. **Turbo boost leak or failing turbocharger** (less common), $150-$2,500. On turbocharged engines, the turbo pushes extra air into the engine for power. A split intercooler hose, loose clamp, stuck wastegate or worn turbo lets that pressure escape, so acceleration feels much weaker than normal. You may hear a hiss or whoosh under load, and the computer may cut power and set a boost code. How to confirm: Your car has a turbo, power drops mainly when boost should build, you hear hissing under load, and a scan shows P0299 or a boost-related code. Fix: Replace the leaking hose or clamp, or repair the turbo. ## How to narrow it down at home 1. Have the codes read at a parts store or with a scan tool. Misfire, lean, airflow, fuel pressure, boost or transmission codes point straight to the system involved. 2. Note when the power loss happens: at all speeds, only uphill or with a load, only when hot, or getting worse the longer you accelerate. 3. Check the engine air filter for heavy dirt, and look for a flashing check engine light, which means a severe misfire that can damage the converter. ## Is it safe to drive? > **Drive to a shop this week.** Usually you can drive carefully to a shop, but give yourself extra room when merging or passing. Stop driving if the check engine light flashes, the car will not keep up with traffic, it goes into limp mode, or you smell fuel or see smoke. ## When does it become urgent? - The check engine light flashes: ease off and stop driving soon, because a severe misfire can ruin the converter. - The car goes into limp mode and will not exceed a low speed or shift past a low gear. - You smell raw fuel or see smoke from the engine or exhaust. - The car cannot keep up with traffic on a highway or hill, making merging unsafe. - The engine shakes hard, knocks or stalls under acceleration. ## What will the repair cost? | Cause | Fix | Typical cost | | --- | --- | --- | | Misfire from worn spark plugs or a failing coil | Replace the spark plugs or the failing ignition coil | $150-$600 | | Weak fuel pump or clogged fuel filter | Replace the fuel pump or fuel filter | $150-$1,300 | | Dirty or failing mass airflow sensor or clogged air filter | Replace the air filter, clean or replace the MAF sensor | $20-$450 | | Clogged catalytic converter | Replace the catalytic converter (and fix what clogged it) | $1,000-$2,500 | | Turbo boost leak or failing turbocharger | Replace the leaking hose or clamp, or repair the turbo | $150-$2,500 | Detailed breakdowns: [spark plug replacement cost](/cost/spark-plug-replacement), [ignition coil replacement cost](/cost/ignition-coil-replacement), [fuel pump replacement cost](/cost/fuel-pump-replacement), [mass air flow sensor replacement cost](/cost/mass-air-flow-sensor-replacement), [catalytic converter replacement cost](/cost/catalytic-converter-replacement). ## What to tell your mechanic Tell the shop when power drops (uphill, merging, hot, cold, at a certain speed), whether it stumbles, sags or feels like the brakes are on, and whether the check engine light was steady or flashing. They will read codes and freeze-frame data, check misfire counts and fuel trims, test fuel pressure, inspect the air intake and check exhaust back pressure. ## How to prevent it - Replace spark plugs at the interval in your owner's manual, often 60,000 to 100,000 miles. - Change the engine air filter on schedule, sooner if you drive on dusty roads. - Avoid running the fuel tank close to empty, which can shorten fuel pump life. - Fix a check engine light or misfire promptly so it does not damage the converter. - Use the fuel grade your owner's manual recommends, especially on turbocharged engines. ## Which models get the most fuel and propulsion complaints? | Model | Fuel and propulsion complaints to NHTSA | All complaints | | --- | --- | --- | | [Honda CR-V](/vehicles/honda-cr-v) | 1,177 | 8,952 | | [Ram 1500](/vehicles/ram-1500) | 724 | 7,390 | | [Honda Accord](/vehicles/honda-accord) | 708 | 5,912 | | [Honda Pilot](/vehicles/honda-pilot) | 571 | 5,776 | | [Toyota RAV4](/vehicles/toyota-rav4) | 473 | 4,051 | | [Jeep Grand Cherokee](/vehicles/jeep-grand-cherokee) | 423 | 5,477 | | [Ford Escape](/vehicles/ford-escape) | 409 | 10,274 | | [Hyundai Tucson](/vehicles/hyundai-tucson) | 401 | 5,363 | | [Chevrolet Equinox](/vehicles/chevrolet-equinox) | 387 | 3,179 | | [Ford Explorer](/vehicles/ford-explorer) | 353 | 9,238 | Owner complaints filed with NHTSA in the fuel and propulsion category for 2015-2026 models of 63 popular cars. Counts follow sales as well as reliability, so compare each with the model's total. ## Trouble codes that often go with it - [P0300](/codes/p0300): Random/Multiple Cylinder Misfire Detected - [P0101](/codes/p0101): Mass or Volume Air Flow "A" Circuit Range/Performance - [P0171](/codes/p0171): System Too Lean (Bank 1) - [P0174](/codes/p0174): System Too Lean (Bank 2) - [P0087](/codes/p0087): Fuel Rail/System Pressure - Too Low - [P0299](/codes/p0299): Turbocharger/Supercharger "A" Underboost Condition - [P0420](/codes/p0420): Catalyst System Efficiency Below Threshold (Bank 1) ## Frequently asked questions ### Why does my car lose power when I press the gas? Most often because of a misfire from worn spark plugs or a bad coil, a weak fuel pump or clogged filter, or a dirty mass airflow sensor. Each limits what the engine can deliver under load. Reading the codes is the fastest way to tell which one you have. ### Can I drive with my car losing power? Usually you can drive carefully to a shop, leaving extra room when merging and passing. Stop if the check engine light flashes, the car enters limp mode, or you smell fuel or see smoke, because those can mean severe damage or a safety risk if you keep driving. ### How much does it cost to fix a car that loses power? It depends on the cause. An air filter or MAF cleaning can cost under 100 dollars, spark plugs or a coil 150 to 600, a fuel pump 500 to 1,300, and a catalytic converter 1,000 to 2,500 dollars at an independent shop in 2026. ### What is limp mode? Limp mode is a protective setting where the engine computer cuts power, limits engine speed or holds the transmission in one gear after it detects a serious fault. It lets you reach safety or a shop slowly. The check engine or transmission light is usually on, and stored codes show why. ### Can a clogged fuel filter cause loss of power? Yes, a clogged filter restricts fuel flow, and the engine runs short of fuel when demand is highest, such as hard acceleration or climbing hills. Many newer cars have the filter built into the fuel pump module in the tank, so the fix may mean replacing that assembly. ### Can a bad catalytic converter cause loss of power? Yes, a converter that melts or clogs inside blocks the exhaust, so the engine cannot breathe out. Power drops more the longer you accelerate, and the car may struggle to reach highway speed. Fix the misfire or oil burning that caused it, or the new converter can fail too. ### Why does my car lose power going uphill? Climbing a hill puts the engine under its heaviest steady load, so a weak fuel pump, clogged filter, misfire, clogged converter or slipping transmission shows up there first. If revs climb without speed, suspect the transmission; if revs and speed both sag, suspect fuel, spark or exhaust. ### Can a dirty air filter make my car slow? A very dirty air filter can reduce power at full throttle on older engines, though modern engines usually compensate well at normal driving. It is cheap and quick to check, so it is worth replacing if it looks clogged. Do not expect it to fix a serious power loss alone. ### Is losing power the same as hesitation? Not quite. Hesitation is a brief stumble or delay when you first press the gas, while losing power is weak acceleration that lasts or gets worse under load. The causes overlap, including misfires and fuel or airflow problems, so the same checks and codes help with both. ### Can the transmission cause loss of power when accelerating? Yes, a slipping transmission lets engine revs rise without the car speeding up, which feels like power loss. A torque converter problem can feel similar. If the tachometer climbs but speed does not follow, the transmission is a stronger suspect than the engine. ## Sources - [Car Care Council: Car care guide](https://www.carcare.org/car-care-guide/) - [EPA: On-Board Diagnostics (OBD)](https://www.epa.gov/state-and-local-transportation/vehicle-emissions-board-diagnostics-obd) - [AAA: Approved Auto Repair](https://www.aaa.com/autorepair/) ## Other car problems - [Why is blue smoke coming from my exhaust?](https://diagxcar.com/symptoms/blue-smoke-from-exhaust) - [Why does my car smell like something is burning?](https://diagxcar.com/symptoms/burning-smell-from-car) - [Why does my car crank but not start?](https://diagxcar.com/symptoms/car-cranks-but-wont-start) - [Why does my car hesitate when I accelerate?](https://diagxcar.com/symptoms/car-hesitates-when-accelerating) - [Why does my car jerk when I accelerate?](https://diagxcar.com/symptoms/car-jerks-when-accelerating) - [Why is my car leaking oil?](https://diagxcar.com/symptoms/car-leaking-oil) - [Why does my car shake at idle?](https://diagxcar.com/symptoms/car-shakes-at-idle) - [Why does my car shake when I accelerate?](https://diagxcar.com/symptoms/car-shakes-when-accelerating) - [Why is my car overheating?](https://diagxcar.com/symptoms/car-overheating) - [Why is my car leaking transmission fluid?](https://diagxcar.com/symptoms/car-leaking-transmission-fluid) ## Repair costs - [Spark plug replacement cost](https://diagxcar.com/cost/spark-plug-replacement): $120-$450 - [Ignition coil replacement cost](https://diagxcar.com/cost/ignition-coil-replacement): $150-$400 - [Fuel pump replacement cost](https://diagxcar.com/cost/fuel-pump-replacement): $450-$1,300 - [Mass air flow sensor replacement cost](https://diagxcar.com/cost/mass-air-flow-sensor-replacement): $150-$450 - [Catalytic converter replacement cost](https://diagxcar.com/cost/catalytic-converter-replacement): $1,000-$3,000 - [Engine replacement cost](https://diagxcar.com/cost/engine-replacement) - [Knock sensor replacement cost](https://diagxcar.com/cost/knock-sensor-replacement) ## How long parts last - [How long does a fuel pump last?](https://diagxcar.com/how-long/fuel-pump): 100,000+ miles - [How often should you change your spark plugs?](https://diagxcar.com/how-often/change-spark-plugs): 30,000-100,000 miles - [How often should you replace your air filter?](https://diagxcar.com/how-often/replace-air-filter): Every 15,000-30,000 miles - [How long do catalytic converters last?](https://diagxcar.com/how-long/catalytic-converter): 10 years or more ## Trouble codes that lead here - [P0017 Crankshaft Position - Camshaft Position Correlation (Bank 1 Sensor B)](https://diagxcar.com/codes/p0017) - [P0018 Crankshaft Position - Camshaft Position Correlation (Bank 2 Sensor A)](https://diagxcar.com/codes/p0018) - [P0019 Crankshaft Position - Camshaft Position Correlation (Bank 2 Sensor B)](https://diagxcar.com/codes/p0019) - [P0122 Throttle/Pedal Position Sensor/Switch "A" Circuit Low](https://diagxcar.com/codes/p0122) - [P0123 Throttle/Pedal Position Sensor/Switch "A" Circuit High](https://diagxcar.com/codes/p0123) - [P0201 Injector Circuit/Open - Cylinder 1](https://diagxcar.com/codes/p0201) - [P0307 Cylinder 7 Misfire Detected](https://diagxcar.com/codes/p0307) - [P0326 Knock Sensor 1 Circuit Range/Performance (Bank 1 or Single Sensor)](https://diagxcar.com/codes/p0326) - [P0327 Knock Sensor 1 Circuit Low (Bank 1 or Single Sensor)](https://diagxcar.com/codes/p0327) - [P0332 Knock Sensor 2 Circuit Low (Bank 2)](https://diagxcar.com/codes/p0332) - [P0352 Ignition Coil "B" Primary/Secondary Circuit](https://diagxcar.com/codes/p0352) - [P0421 Warm Up Catalyst Efficiency Below Threshold (Bank 1)](https://diagxcar.com/codes/p0421) --- Source page: https://diagxcar.com/symptoms/car-loses-power-when-accelerating Updated: 2026-11-03 General information, not a substitute for a qualified mechanic.