Car Losing Power When Accelerating: Common Causes
Written by Petro Olekhnovych, mobile mechanic in Aylesham, Kent
A car losing power when accelerating is usually caused by a problem with air, fuel, spark or exhaust flow, or by a fault that has put the car into “limp mode”. Common culprits are blocked filters, worn spark plugs, faulty sensors, dirty injectors and a blocked exhaust or diesel particulate filter. If power drops suddenly, stay calm, pull over when safe and check your dashboard warning lights.
What losing power feels like
The RAC says power loss is most noticeable when you accelerate, but it can also happen at a steady speed or come and go.
You might notice:
- The car is slow to pick up speed, even with your foot down.
- It struggles on hills or when loaded up.
- The revs rise but the car does not speed up.
- It hesitates, stutters or jerks.
- A warning light comes on at the same time.
How it feels gives useful clues. Make a note of when it happens: cold or warm, on hills, at a certain speed, or all the time.
Common causes of a car losing power when accelerating
These are the causes listed by the RAC and Kwik Fit. Your car may have just one, or a mix.
Blocked air filter. A clogged filter restricts the air the engine breathes. That weakens acceleration and can increase fuel use.
Blocked fuel filter, weak fuel pump or dirty injectors. These interrupt fuel delivery. Kwik Fit says this can cause hesitation, rough idling or misfires.
Worn spark plugs (petrol) or glow plugs (diesel). Poor combustion leaves the engine sluggish.
Engine misfire. If one cylinder is not firing, you lose power and the engine may shake. Read our guide to engine misfire symptoms for more.
Faulty sensors. A sensor such as the mass air flow (MAF) sensor can send wrong data to the engine computer, which then cuts power.
Blocked exhaust, catalytic converter or DPF. If exhaust gases cannot get out, the engine cannot breathe properly. The RAC says a lack of power and acceleration is the first sign of a blocked catalytic converter.
Turbo problems. A turbo that is not working properly can drag power down instead of boosting it.
Slipping clutch. On a manual car, the revs climb but the car does not gain speed as it should. Kwik Fit says this is most obvious on hills or with extra weight.
Binding brakes. A stuck brake caliper, or a handbrake that does not fully release, holds a wheel back. Kwik Fit warns this can affect safety.
Tyres. Low pressure or badly worn tyres make the car less responsive.
General wear. Parts wear over time. The RAC advises keeping up with servicing and acting on MOT advice.
Warning light on? We come to you.
Send a photo of the dashboard and your reg. We will tell you if it looks safe to drive and what it needs.
WhatsApp for a free quote Call 07563 350335
Labour £30 to £50 per hour depending on the job. Send your reg number and we will reply with a price before any work starts.
What is limp mode?
Limp mode is a protective setting. When the engine computer spots a serious fault, it limits power so the car can still move without causing more damage.
Carwow says limp mode can cap the revs at around 2,000 to 3,000rpm and limit top speed. Automatic cars may be held in a low gear. Warning lights usually come on.
Causes include very low oil or coolant, sensor faults, wiring problems, transmission faults and engine problems such as misfiring or turbo faults. On diesels, the RAC says a clogged DPF can trigger it.
Switching off and restarting may clear the warning for a while. Carwow points out that this does not fix the underlying fault. If limp mode comes back, get the car checked.
Is it safe to keep driving?
Be cautious. A car that cannot accelerate properly is risky when joining a fast road or overtaking.
- If you lose power on a busy road, put your hazard lights on and pull over safely.
- If the engine light is flashing, or any warning light is red, the AA says to stop as soon as it is safe and switch off.
- If you see the oil or temperature warning light, stop and do not keep driving.
- If the brakes feel wrong or the car pulls to one side, stop. Binding brakes are a safety issue.
The RAC also advises letting the engine cool and restarting if the computer has cut power. If the problem stays, get it looked at. Carwow advises recovery rather than driving far or on fast roads in limp mode.
How the cause is found
Power loss has so many possible causes that a diagnostic check is the sensible first step. It reads any fault codes the engine computer has stored.
The codes point in the right direction. A mechanic then checks the likely parts to confirm the actual fault before replacing anything.
What it costs and why it varies
There is no single price, because the cause decides the repair. Changing a blocked air filter is a small job. A turbo or clutch problem is a much bigger one.
Cost depends on:
- What the fault is.
- Your car’s make, model and engine.
- The parts your car needs.
- How long it has been left. The RAC warns that some causes, such as faulty injectors or a blocked exhaust, can lead to costly engine damage.
Filters and other service parts wear out at different rates on different cars. Check your handbook or service book for your car’s intervals. Our car service checklist explains what a service should cover.
How we can help
We are a mobile mechanic and we come to you, at home or at work. We cover Aylesham, Canterbury, Dover, Deal, Sandwich, Folkestone and nearby villages. If you are near Canterbury, see our mobile mechanic Canterbury page.
We can come out and diagnose the cause of the power loss, then tell you what it needs. We replace air filters and fuel filters (petrol and diesel), and we carry out servicing. For other faults, we will explain what we found and what the next step is.
Labour is £30-£50 per hour, depending on the job and its difficulty. Parts are extra. We agree the price with you on WhatsApp before any work starts.
Frequently asked questions
Why does my car lose power going uphill?
Hills put the engine under more load, so weak spots show up. Common causes include blocked filters, fuel delivery problems and, on manual cars, a slipping clutch.
Can a dirty air filter cause loss of power?
Yes. Kwik Fit says a clogged air filter restricts airflow, which weakens acceleration and increases fuel use.
Will restarting the car fix limp mode?
It may clear the warning for a while, but it does not fix the fault. If it comes back, get the car diagnosed.
Need help? Send a WhatsApp to 07563 350335 with your car’s make and model and we’ll come to you.
Warning light on? We come to you.
Message us on WhatsApp with your reg and postcode for a price before any work starts.
WhatsApp for a free quote Call 07563 350335
Labour £30 to £50 per hour depending on the job. Send your reg number and we will reply with a price before any work starts.
