1. A bad spark plug wire
   A clogged fuel injector
2. A worn spark plug
   Any of these could do it

If your car's engine is shaking so badly you can feel it in both your steering wheel and your seat, there's a misfire problem, often indicating a worn spark plug, a bad spark plug wire or a clogged fuel injector.

1. It's cold outside.
   The engine is flooded.
2. The engine has seized up.
   There's coolant loss.

Together these symptoms usually indicate the car's engine is flooded. Now what?

1. Loose fan belt
   Loose engine block
2. Loose cylinder heads
   Bad motor mounts

Excessive engine vibration, usually because bad motor mounts aren't holding it securely, can be felt on the passenger's side of the car.

1. Air/fuel mixture
   Compression
2. Propulsion
   Spark

For your car's engine to start, it needs to have good air/fuel mixture, compression and a spark (provided, of course, by the ignition).

1. Damaged rod bearings
   Damaged wheel bearings
2. Worn front axle
   Worn control arm bushings

A deep knocking that sounds more like hammering than pinging is called a "rod knock." This happens from wear-and-tear or damage to the rod bearings — and it's a fatal engine problem.

1. Antifreeze (or water) contamination
   Gasoline contamination
2. Transmission fluid contamination
   Washer fluid contamination

Motor oil changes color from nearly clear or amber to dark brown and almost black, depending on how dirty it is. But if it's a foamy, milky white, that means some antifreeze (or water) has contaminated it, and you'll want to look into what could be leaking from the car's cooling system.

1. Broken wrist pin
   Damaged cylinder liners
2. Damaged piston rings
   Part that connects piston to crankshaft is broken

"Throwing a rod" means a connecting rod, which connects a piston and the crankshaft, has broken. It makes a sound exactly like you'd think — a metal rod knocking under the hood, doing all kinds of damage — and is pretty much guaranteed to ruin your day. Don't even try driving it to the shop, just pull over and call a tow.

1. Wait at least 15 minutes, then start engine while holding the gas pedal to the floor.
   Pump the gas pedal while cranking the engine.
2. Check your oil.
   Buy a car without a carburetor.

This can happen when the mixture of fuel and air gets off balance, most commonly in cars that have a carburetor instead of fuel injection. The best way to solve it is to let the excess fuel evaporate, so wait as long as you can, and then try to start the engine while holding the gas pedal to the floor — but be careful NOT to pump it. Pumping the pedal might be what got you in this predicament to begin with.

1. Antifreeze
   Brake fluid
2. Power steering fluid
   Transmission fluid

Ethylene glycol antifreeze is that green, orange or yellow sweet-smelling fluid. The first symptom of a leak? If you don't notice the indicator lamp, you will notice when your car's engine overheats. Antifreeze is lethal but tasty to cats, dogs and other animals, so be sure to clean up these puddles as much as possible.

1. Bubbles in the radiator
   Complete engine failure
2. Engine sputter
   Loud clunking noises

Although all of these are symptoms your car's engine has seized or is about to seize, the most common sign is complete engine failure. Which is exactly as bad as it sounds.

1. Fuel line obstruction
   Damaged fuel injectors
2. Air filter problem
   It could be option 2 or 3, but not usually 1

Black smoke coming from a car's exhaust pipe can happen because the engine is flooded with gasoline, typically by damaged fuel injectors and sensors. Black smoke can also mean a problem with your car's air filter, too.

1. Clogged fuel filter
   Dirty spark plugs
2. Damaged spark plug wires
   Any of these

When your car feels sluggish and you can hear popping from under the hood, it could be lots of things, among them: dirty or damaged spark plugs (and their wires), a clogged fuel filter, other ignition problems, or trouble with the car's catalytic converter.

1. Performance problems
   Clogged fuel injectors, filters and lines
2. Fatal engine damage
   All of these

Diesel is thicker than gasoline, which means as soon as you started the car, the diesel went to work clogging your gasoline-powered engine's fuel injectors, filters and lines. If your car makes it home and continues to start, you'll feel timing and performance problems before the engine finally gives up the ghost.

1. Brown
   Clear
2. Orange
   Red

An oil spot under your car will be brown fluid. Most of the time, it'll be because of wear-and-tear on gaskets, seals and connections — and don't forget to check the oil pan seals, which are under the car.

1. Carbon buildup
   Bad spark plugs
2. Low fuel octane
   Any of these could cause knocking

There are a few reasons, and degrees of severity, for your engine to start pinging or knocking at you. It happens because of a problem with the air-fuel mixture, and could mean any of the following: You need to use a different fuel octane, there may be carbon buildup, or the spark plugs need replacement. Left unfixed, it can do some serious engine damage.

1. True
2. False

The thermostat's job is to block the flow of coolant to the radiator until the engine has warmed up. A broken thermostat won't let coolant reach a hot engine, thus causing it to overheat.

1. Damaged head gasket
   Overheating engine
2. Cracked engine block
   It could be any of these three problems

On a cold morning you may notice white vapor coming from your exhaust pipe. It's normal and stops as soon as your car warms up — probably no longer than 20 minutes. But if it's white smoke coming from your car's exhaust pipe, that can be caused by all of these problems.

1. Excessive antifreeze consumption
   Excessive oil consumption
2. Loss of power, both overall and during acceleration
   Overall poor driving performance

Excessive oil consumption as well as poor performance and loss of power are all common symptoms of worn piston rings.

1. Bad catalytic converter
   Dirty air flow sensor
2. Loose gas cap
   Oil change reminder

The check engine light, also known as the malfunction indicator light, will trigger for a lot of things, including a bad catalytic converter, dirty air flow sensor or even a loose gas cap. But if you forget to change your oil, it won't give you reminders before the damage is done.

1. Bad ignition coil
   High oil pressure
2. Low oil pressure
   Wrong octane gas

Also called "run-on," this mostly happens when you fill up with the wrong octane gas for your car. Both a failing solenoid or an overactive carburetor could also cause the problem.

1. Water is mixing into the engine oil
   An oil or antifreeze leak
2. A misaligned water pump
   A damaged drive belt

Sizzling indicates there's a fluid — engine oil or antifreeze — leaking onto something hot, like the exhaust manifold.

1. Fuel
   Oil
2. Transmission fluid
   Water

If your engine is surging, it's a sign that it's not getting the right fuel mix or enough of it.

1. Defective cam lobes
   Defective valve train push rods
2. Defective valve train rocker arms
   Defective valve train valve lifters

Clicking noise, also called "chatter," is the sound of your car's valve train, specifically defective hydraulic valve lifters (also known as hydraulic tappets).

1. Coolant
   Gasoline
2. Oil
   Transmission fluid

Blue smoke indicates there's a problem with leaking and burning oil.

1. A change in fuel economy, for the worse
   Engine knocking
2. Stalling
   Sulfur smell in the passenger cabin

You'll know your car's MAF is bad because it can decrease your car's fuel economy by as much as 25 percent. Ouch.

1. Engine control module
   Engine control unit
2. Power control module
   These are all the same thing

The engine control module (ECM), also known as the engine control unit (ECU) or powertrain control module (PCM), handles the engine's performance.

1. Worn piston rings
   Piston slap
2. Low piston ring tension
   Cracked or burned piston

"Piston slap," the sound a piston makes when it rocks back and forth inside a cylinder, sounds a lot like a bell.

1. Bad crank position sensor
   Bad ignition coil
2. Broken timing belt (or chain)
   Engine vacuum leak

Poor gas mileage and stalling, as well as rough idling and/or a hissing sound from under the hood, can be symptoms of an engine vacuum leak.

1. Bad oil pump
   Faulty oil pressure sending unit
2. Low oil level
   Worn engine bearings

First, check that your oil level isn't low. Not the problem? It could be oil pressure. If that's not about 10 PSI for every 1,000 RPMs of engine speed, it could be a bad oil pump, in which case the oil-pressure sending unit could be on the fritz. But the worst scenario is worn engine bearings, which means your engine will need to be either rebuilt or replaced.

1. Engine won't start
   Moisture on the distributor cap
2. Service engine soon light
   Overheating

The most common three engine problems: It won't start, it overheats, or the "service engine soon" light comes on.

1. A loose hose is touching a hot part of the engine.
   The engine is overheating.
2. There's burned oil in the engine area.
   Oil is leaking onto the engine block.

A sweet, steamy smell inside your car indicates a coolant problem, for any number of reasons, most of which point to the engine overheating.

1. Low piston ring tension
   Worn piston pins
2. Worn piston rings
   Broken valve spring

Faulty piston pins cause engine noise, but it's a really specific type of 'secret knock': a metallic-sounding double knock, usually most noticeable at idle.

1. Check for signs the engine is misfiring.
   Shut your car off, and restart it.
2. Tighten the car's gas cap.
   Ignore it.

A flashing check engine light means the problem is more serious than a loose gas cap. Check for signs that your car's engine is misfiring, a serious problem that could cause damage to the catalytic converter.

1. Rust accumulation
   Lack of oil
2. A loose piston that's become lodged
   A damaged engine cylinder

Your car's engine may seize if there's a lack of oil, if there's rust accumulation, and if there's a mechanical issue like a loose piston that's become lodged.