Diagnose
Car problems, explained by symptom
Start with what your car is actually doing — a noise, a vibration, a smell, a light. Every guide tells you the likely causes, whether it is safe to keep driving, and what a repair should cost.
Browse by system
Nine systems cover almost everything that goes wrong on a modern car.
- EngineEngine ProblemsRough running, misfires, power loss, noise and warning lights.
- TransmissionTransmission ProblemsSlipping, harsh shifts, delayed engagement and fluid issues.
- BrakesBrake ProblemsVibration, noise, soft pedal, pulling and warning lights.
- SuspensionSteering & SuspensionPulling, clunks, uneven tire wear and vague steering.
- ElectricalElectrical ProblemsDead accessories, flickering lights, modules and wiring faults.
- AC & HeatingAC & Heating ProblemsWeak cooling, no heat, odors and blower failures.
- BatteryBattery & ChargingDead batteries, parasitic drain, alternator and charging faults.
- ExhaustExhaust & EmissionsCatalytic converters, oxygen sensors, EVAP and emissions failures.
- BatteryStarting ProblemsNo crank, slow crank, clicking and cranks-but-won't-start.
All problem guides
22 symptom-first diagnostic guides.
- Moderate
Car Shakes When Braking
A shudder felt through the steering wheel or brake pedal when slowing down, usually from uneven rotor thickness.
8 min readUpdated August 24, 2026
- High
Car Won't Start
No crank, a single click, rapid clicking or endless cranking — each sound points at a different failure and a different repair.
9 min readUpdated August 15, 2026
- Moderate
Car Battery Keeps Dying
A battery that goes flat repeatedly is one of three things: a battery that no longer holds charge, an alternator that stopped replacing it, or something in the car staying awake overnight.
10 min readUpdated August 9, 2026
- Critical
Car Overheating
Temperature gauge climbing into the red, steam from under the hood, or a coolant warning — almost always a leak, a stuck thermostat or a fan that stopped working.
10 min readUpdated July 22, 2026
- Low
Car AC Not Cooling
Air comes out of the vents but it is not cold — nearly always low refrigerant from a leak, a compressor that will not engage, or a blocked airflow path.
9 min readUpdated August 11, 2026
- Moderate
Car Pulls to One Side
A steady drift toward the left or right that makes you hold the wheel off-center — usually tire pressure, alignment, or a dragging brake caliper.
9 min readUpdated June 30, 2026
- Moderate
Clicking Noise When Turning
A rhythmic click or pop that appears only while the wheel is turned — on a front-wheel-drive car this is an outer CV joint until proven otherwise.
8 min readUpdated May 19, 2026
- Moderate
Car Shakes at High Speed
A vibration that appears at high speed — usually somewhere between 50 and 80 mph, or roughly highway pace — and is there whether you accelerate, coast or brake. Nearly always tire balance, a bent wheel or a damaged tire.
11 min readUpdated August 24, 2026
- Moderate
Car Shakes When Idling
Shaking that appears at a stop and smooths out on the move usually traces to a misfire, a vacuum leak, a failed motor mount, or the idle-control system losing its target — four different repairs at four different price points.
9 min readUpdated August 24, 2026
- High
Smoke From the Exhaust
The color of the smoke tells you which fluid is getting into the combustion chamber, and that single observation decides whether this is nothing, a repair, or a reason to stop driving.
7 min readUpdated August 24, 2026
- Critical
White Smoke From Exhaust
Thin white vapor that clears once the engine warms up is condensation and normal. Thick white smoke that keeps going after the engine is hot is coolant burning in the cylinders.
11 min readUpdated August 24, 2026
- High
Blue Smoke From Exhaust
Blue or blue-gray smoke is engine oil burning in the cylinders. When it happens tells you which path the oil is taking — a puff at startup points at valve seals, a steady stream under load points at piston rings.
11 min readUpdated August 24, 2026
- Moderate
Black Smoke From Exhaust
Black smoke is soot from unburned fuel — the engine is running rich. The cause is often as cheap as a clogged air filter, but left alone it destroys catalytic converters and fails emissions tests.
11 min readUpdated August 24, 2026
- High
Transmission Slipping
Slipping means engine speed and road speed have come apart — the engine revs but the car does not respond. The whole diagnostic question is whether the friction material is worn out or the hydraulics that squeeze it have failed, because one means a teardown and the other often does not.
13 min readUpdated August 24, 2026
- Moderate
Transmission Shudder (Torque Converter Shudder)
A rumble-strip vibration at steady light-throttle cruise, while the transmission is not shifting. It is almost always the torque converter's lockup clutch failing to clamp cleanly — and caught early it is often a fluid job rather than a converter.
12 min readUpdated August 24, 2026
- High
CVT Transmission Problems
A continuously variable transmission transmits power through friction between a steel belt and two movable pulleys, with no fixed gears and no mechanical fallback. That single design fact explains its failure modes, why the fluid specification is not negotiable, and why a failed CVT is usually replaced rather than rebuilt.
14 min readUpdated August 24, 2026
- Moderate
Car Jerks When Accelerating
Most people arrive here worried about the transmission. Usually it is not — jerking under acceleration is far more often an engine fuel, ignition or air problem. This page sorts the causes by exactly when the jerk happens, so you know which repair you are actually facing.
12 min readUpdated August 24, 2026
- High
Coolant Leak
A puddle under the front of the car, a reservoir that keeps dropping, or a sweet smell after shutdown. Where the leak is matters far more than how big it looks — and the honest answer to "how far can I drive" is not a number.
14 min readUpdated August 24, 2026
- Moderate
Engine Oil Leak
A dark puddle where you parked, a burning smell, or a dipstick that keeps reading low. Finding out whether it is leaking from the top or the bottom of the engine narrows the answer faster than anything else — and the cost depends almost entirely on which gasket it is.
14 min readUpdated August 24, 2026
- Moderate
Car Electrical Problems
Something electrical is wrong and you do not yet know which part. This page is a triage tool: match your symptom to a subsystem, work through the checks in the right order, and know what a shop will charge just to find the fault.
13 min readUpdated August 24, 2026
- Moderate
Car Alarm Keeps Going Off
How to silence it right now, what is most likely triggering it, and how to stop it recurring. Owner reports filed with NHTSA point at one cause more than any other — and it is not the one most articles lead with.
13 min readUpdated August 24, 2026
- Moderate
Parasitic Draw
A parasitic draw is current the car keeps pulling after you lock it and walk away. Finding one is a measurement problem before it is a repair problem, and most people measure it wrong.
12 min readUpdated August 24, 2026