When a car feels sluggish, struggles up hills, or needs gas more often than it used to, the engine is not turning fuel into power the way it should. The cause is usually air, fuel, spark, exhaust flow, or something outside the engine that makes it work harder. Many of these problems start small and get worse slowly, so falling gas mileage is often the first warning you get.
You may notice the car takes longer to get up to freeway speed, or it feels weak climbing the hills north of Foothill. You might press the pedal further than you used to for the same speed. Or nothing feels different, but you are stopping at the gas station more often. Some cars also turn on the check engine light, but many of these problems build for a while before any light comes on.
The engine needs clean air and steady fuel. A dirty air filter or a clogged fuel filter can limit what gets in. These are simple maintenance items, but they are easy to forget, and they are among the first things we check.
Spark plugs wear a little every mile. A tired plug or a weak ignition coil gives a weaker spark, so some fuel does not burn fully. You lose power and mileage at the same time. A bad misfire often turns on the check engine light. If that light is flashing, stop driving, because a severe misfire can damage the catalytic converter.
The engine computer decides how much fuel to add based on its sensors. A dirty mass airflow sensor, a slow oxygen sensor, or a coolant temperature sensor that reads cold can make it add too much or too little fuel. Too much fuel wastes gas. Too little costs power. Because the engine is only acting on bad information, these problems can be hard to spot without live data.
Dirty fuel injectors or a fuel pump that cannot keep up can starve the engine when you ask for power. You may feel this most going uphill, passing, or merging. It often shows up together with hesitation when you accelerate.
If the exhaust cannot get out, fresh air cannot get in. A clogged catalytic converter makes the car feel weak, especially at higher speed, and it may run hot. A converter usually fails because of another problem upstream, such as a misfire or burning oil. That cause has to be found too, or a new converter can fail the same way.
Not every power or mileage problem is in the engine. Low tire pressure, a brake that drags, a transmission that slips, or extra weight in the car all make the engine work harder. Checking these first can save you money. If your car slips or shifts late, see our post on signs your transmission needs service.
Check the easy things yourself: tire pressure, and whether your driving changed, like more short trips or more AC use in hot weather. If the car still feels weak or your mileage keeps dropping, have it looked at. Get it checked right away if power drops suddenly, the check engine light flashes, the car will not go over a certain speed, or you smell fuel or something hot.
Many of these causes feel the same from the driver's seat. Replacing parts one at a time gets expensive fast. At 123 Auto Center in Upland we read the live engine data, check fuel and exhaust flow, and test each system to find the real cause, so you fix it once. Our diagnostic rate is $145/hour, and the first hour is applied toward your repair when the total is over $250. Learn more about our engine diagnostics and pricing, or read our full engine performance and drivability guide.
Schedule a Diagnostic Call (909) 527-2525
Is it safe to drive a car that is losing power?
A slow drop in power can usually wait a few days for an appointment. Sudden power loss, a flashing check engine light, or a car that will not go over a certain speed is different. Stop driving and have it checked, because it can be unsafe on the freeway and can cause more damage.
Why did my gas mileage suddenly drop?
Common reasons include low tire pressure, a dragging brake, worn spark plugs, a dirty air filter, or a sensor that tells the engine to add too much fuel. Hot weather with the AC on and short trips also lower mileage, so compare similar driving before you worry.
Can a clogged catalytic converter cause power loss?
Yes. A restricted converter backs up the exhaust, and the engine cannot breathe out. The car feels weak, especially uphill or at freeway speed. A converter usually clogs because of another problem, like a misfire, so that cause needs to be found and fixed too.
How much does it cost to find out why my car is losing power?
Our diagnostic rate is $145 per hour, and the first hour is applied toward your repair when the repair total is over $250. We find the cause first and give you a clear estimate before any work.
