Use the diagnostic app for acceleration and drivetrain faults
You can use the free Motor Vehicle Expert diagnostic app to compare clutch slip, gearbox slip, loss of power, hesitation, limp mode, burning smells and warning-light symptoms.
Separate slip from low power
Find whether the engine revs freely but speed does not match, or whether the engine itself feels weak.
Compare manual and automatic clues
Manual clutch slip and automatic gearbox slip show similar rev flare but need different checks.
Spot urgent symptoms
Burning clutch smell, sudden loss of drive, warning lights and gearbox faults should be checked quickly.
Choose next steps
Avoid guessing parts before checking clutch, gearbox, drivetrain and engine management clues.
Quick answer
When revs increase but road speed does not match, the fault is commonly clutch slip on manual cars or transmission slip on automatics. Driveshaft, differential, gearbox or reduced-power faults can also create similar symptoms.
Repeated slipping should not be ignored. It can quickly worsen, create burning smells, overheat components and increase repair costs. Avoid hard acceleration until the fault is diagnosed.
If the engine revs rise but the car speed does not follow, think “power transfer” first: clutch, gearbox, driveshafts and transmission. If the revs struggle to rise, think “engine power” first.
Common causes of revs rising without acceleration
Clutch slip
Very common on manual cars, especially in higher gears, uphill or under load.
Clutch wear signs →Automatic gearbox slip
Revs flare while speed lags behind, often worse when hot or changing gear.
Transmission fluid issue
Low, old or incorrect fluid can affect some automatic gearboxes.
Driveshaft fault
A damaged driveshaft or CV joint can stop drive transferring properly to the wheels.
CV joint noise guide →Differential issue
Less common, but drivetrain noise or loss of drive can point towards differential faults.
Reduced-power mode
Limp mode can feel like no acceleration, but usually the revs do not flare like a slipping clutch.
Engine light guide →Dual mass flywheel issue
Often appears with clutch wear, vibration, rattling or juddering when pulling away.
Juddering guide →Gearbox internal wear
Worn internal parts can cause slipping, delayed drive or poor gear engagement.
Engine power fault
Turbo, fuel, misfire or sensor faults can feel slow but are not the same as true slip.
Slow acceleration guide →Manual cars: is it clutch slip?
On manual cars, clutch slip is one of the most common explanations. Engine revs rise quickly, but the vehicle does not accelerate in proportion because the clutch is no longer gripping properly.
- ✓Worse in higher gears such as 4th, 5th or 6th.
- ✓Worse uphill, towing or with passengers.
- ✓Burning clutch smell may appear after acceleration.
- ✓Bite point may feel higher than normal.
- ✓Acceleration feels worse even though the engine sounds busy.
Useful guides: clutch wear signs, car smells like burnt clutch and clutch replacement cost UK.
Automatic cars: possible transmission slip
Automatic cars may suffer from internal wear, fluid problems, overheating or control faults that allow revs to rise without matching drive. This can feel like the gearbox is “flaring” between gears or struggling to transfer power.
Harsh or delayed shifts
May happen alongside slipping or flaring.
Delayed drive engagement
Selecting Drive or Reverse may feel slow or hesitant.
Warning light or gearbox message
Transmission or engine warnings may appear with stored fault codes.
Worse when hot
Some transmission faults worsen after driving as fluid and components heat up.
If an automatic gearbox is slipping badly, avoid hard acceleration and arrange diagnosis promptly. Continuing to drive can make internal damage worse.
Helpful clues that narrow the cause
Only on hills
Load-related clutch or transmission slip is likely.
Only in one gear
May point to gearbox-specific issues rather than general engine power.
Noisy drivetrain
Clicking, clunking, whining or grinding can suggest shafts, gearbox or differential faults.
Car noises explained →Warning lights on
Electronic, engine or gearbox faults may be involved and codes should be read.
Warning lights guide →Sudden severe loss of drive
Needs urgent inspection, especially if the car barely moves or will not engage gear.
Is it slip or an engine power fault?
This is an important difference. True slip means the engine revs rise freely but the road speed does not match. An engine power fault means the car feels weak and may not rev properly in the first place.
More like clutch or gearbox slip
Revs rise quickly, speed lags behind, worse uphill, burning smell or gear flare appears.
More like engine power loss
Revs struggle to climb, engine warning light appears, car hesitates, misfires or goes into limp mode.
For engine power-loss symptoms, see car losing power when accelerating, car loses power uphill and can you drive with engine management light on?.
When to stop driving or avoid hard acceleration
- !The clutch or gearbox is slipping badly.
- !The car barely moves even though the engine revs.
- !There is a strong burning clutch or transmission smell.
- !A gearbox warning, engine warning or limp mode message appears.
- !You hear grinding, clunking or loud drivetrain noises.
- !The problem is getting worse quickly.
If the car loses drive in traffic or cannot accelerate safely, stop in a safe place and arrange professional help.
What to check first
- 1Notice whether revs rise faster than road speed.
- 2Check if it is worse uphill, with passengers or in higher gears.
- 3Watch for burning clutch smell or transmission smell.
- 4Check for engine, gearbox or warning lights.
- 5Listen for clicking, clunking, whining or grinding from the drivetrain.
- 6Avoid hard acceleration if slipping badly.
- 7Arrange diagnosis promptly to limit damage.
How a garage usually diagnoses this fault
Road test under load
Confirms whether revs flare without matching acceleration.
Clutch assessment
Checks clutch bite point, slip symptoms, smell, pedal feel and related faults.
Gearbox fault scan
Reads engine and transmission codes where supported by the vehicle.
Transmission fluid check
On suitable vehicles, checks fluid level, condition, leaks and overheating signs.
Driveshaft and mount inspection
Checks CV joints, shafts, engine mounts, gearbox mounts and drivetrain play.
Engine power checks
Rules out limp mode, misfire, turbo, fuel or sensor faults if the symptom is not true slip.
Possible UK repair costs
Repair cost depends on the exact cause, vehicle design, parts quality and labour access. Clutch and gearbox faults are often more expensive than basic engine sensor checks, so correct diagnosis matters.
Clutch replacement
Common on manuals with confirmed clutch slip. Cost depends on labour access and parts.
Clutch cost guide →Dual mass flywheel
May be replaced with the clutch if worn, noisy or damaged.
Automatic gearbox diagnosis
Usually needs proper testing before repair decisions are made.
Transmission fluid service
May help some gearboxes if fluid condition is the issue, but it will not fix severe internal wear.
Driveshaft or CV repair
Costs vary depending on which shaft, joint or related component has failed.
Engine fault diagnosis
Needed if the issue is limp mode, misfire, turbo, fuel or sensor-related power loss.
Engine light guide →Common mistakes drivers make
- !Continuing to accelerate hard when the clutch or gearbox is slipping.
- !Confusing engine power loss with true clutch or transmission slip.
- !Ignoring burning clutch smell after uphill driving or overtaking.
- !Assuming an automatic gearbox only needs fluid without proper diagnosis.
- !Waiting until the car loses drive completely before getting it checked.
- !Replacing engine sensors when the real fault is clutch slip.
Best mechanic-style advice
The key clue is the relationship between revs and road speed. If the revs climb but speed does not follow, suspect slip or drivetrain power transfer. If the revs do not climb properly, suspect engine power loss, limp mode, fuel, turbo or sensor faults.
Do not keep driving hard with confirmed slip. Clutch and gearbox problems usually get worse, and early diagnosis can prevent extra damage.
Related diagnostics guides
Frequently asked questions
Can a worn clutch cause revs to rise but no acceleration?
Yes. It is one of the most common causes on manual cars. The clutch slips instead of transferring power properly to the gearbox and wheels.
Can an automatic gearbox slip?
Yes. Revs may rise while acceleration feels weak or delayed, especially during gear changes or when the gearbox is hot.
Should I keep driving?
Avoid hard acceleration and long journeys if slipping is severe or worsening. Arrange diagnosis before the fault becomes more expensive.
Will it get worse?
Often yes, especially with clutch slip or transmission slip. The fault can progress to poor drive or total loss of drive.
Can engine faults feel similar?
Yes. Limp mode, misfires, turbo faults and fuel problems can mimic poor acceleration, but usually the revs do not flare freely like clutch slip.
Why is it worse uphill?
Hills put more load on the clutch or transmission. Weak grip or internal slip becomes more obvious under load.
What does a burning smell mean?
A burning smell after revving without acceleration can point to clutch overheating or severe transmission slip.
Best next step?
Work out whether it is true slip or engine power loss, then get the clutch, gearbox, drivetrain and fault codes checked promptly.