Can You Diagnose These Engine Problems?


By: Steven Symes

6 Min Quiz

Image: shutterstock

About This Quiz

Do you regularly whisper to car engines? Are people constantly asking you to help them figure out what's wrong with their ride? 

Being able to diagnose engine problems requires you to first know a lot about engines. After all, you can't figure out the cause of a problem if you don't know how things run. Most people know how to diagnose a few simple problems, but being able to correctly diagnose all kinds of engine trouble requires a huge amount of practical knowledge. 

More modern engines often require even more knowledge and equipment to properly diagnose. While a shop can hook the car up to diagnostic equipment and pinpoint a problem with ease, some issues still require mechanics to act like detectives. There are always strange, obscure and particularly vexing engine problems out there, which can puzzle even some of the most experienced in the field. These are often the subjects of discussion on automotive radio shows, forums and websites for mechanics. 

How would you fare at diagnosing engine problems? Are you a pro? Take the quiz now to find out! 

What causes the exhaust to always look white and smell sweet?

Combusting coolant can be from a few different problems. One of the most common is a blown head gasket, but a cracked engine block is another possibility.


What causes an engine to stumble when you press on the accelerator at freeway speeds?

A lean mix, where you have too little fuel in relation to the amount of air, will cause an engine to stumble in these kinds of conditions. The root of this problem can be in the fuel, air intake or ignition systems.


Why would the engine make a rapid clicking noise but not start up?

While most people jump to the conclusion that the battery is bad, this problem could be caused by a bad alternator, blown fuse or other issue with the ignition system.


Why would the traction control and stability control lights come on and stay on after you start up your car?

While there is a possibility you turned these two systems off by pressing buttons in the car, the more likely scenario is there's a fault the ECU detected and you need to have the engine codes read.


What causes flames to shoot out the tailpipe?

If there's way too much fuel being dumped into the cylinders, the unburnt fuel will make its way into the exhaust system where it will then combust, shooting flames out of the tailpipe.


Why would the spark plugs have a white material on them?

Excessive heat will make spark plugs appear this way, which can be from an overheating engine. A lean fuel mixture or improper ignition timing will also cause this problem.


What's wrong with the engine if it squeals on startup?

Squealing is most often a worn or loose belt, but most people fail to realize the pulleys might also be worn and need to be replaced, or the squealing will continue.


What can cause a faint ticking sound to be coming from an engine?

Ticking in your engine is likely coming from the valve train, with oil issues such as a dying pump being perhaps the worst of the potential causes.


What's wrong with the engine if you start seeing blue smoke coming from the exhaust?

Any blue smoke in your exhaust is a sign that oil is making its way into the combustion chambers. The source could be a number of components, like the piston rings or valve guide seals.


What might cause a pinging sound coming from the engine after you've turned it off?

While some people might try to tell you this is detonation, that can only happen when the engine is running. Instead, the sound is the metal on the heat shields contracting, and maybe a few other components, depending on the engine.


What does it mean when the spark plugs are coated with a black liquid?

There are a number of ways oil could be getting into the combustion chambers, like worn piston rings, a cracked piston or old valve guides, to name a few.


If you notice the engine vibrates more than usual when you accelerate, what's likely the cause?

The engine mounts are designed to soak up vibrations from the engine, especially when the engine is under load. If they wear out, you'll notice they don't perform that job as well.


What is the first thing you should check if your engine starts running hotter than normal?

Always use caution when checking the coolant on a hot engine, especially if the overflow reservoir is pressurized, since the coolant could spurt out and burn you.


What's the reason for black exhaust smoke?

There are a few possible causes for this problem, including a clogged air filter, malfunctioning air temperature sensor, malfunctioning MAF, clogged fuel injectors or a malfunctioning fuel pressure regulator.


What could cause the engine RPMs to race as a car is idling?

The fact is that engines can surge when the car's just sitting because of several possible issues, like a problem with the EGR valve, a vacuum leak, too lean of a mixture, or the idle air control motor going bad.


What does it mean if there are dry, black deposits on the spark plugs?

Any number of issues could lead to either cause of this symptom, including a leaking fuel injector, bad oxygen sensor, too high of resistance in the spark plug wires, or a bad distributor, to name a few.


An engine stalls out under load. What's one possible cause?

For an engine to run properly, it needs the proper amount of fuel and air, plus the timing or spark needs to be correct. If any of these elements are off, it can stall.


Steam pours out from under the hood, and it smells sweet. What's the most likely problem?

If the coolant level becomes too low, the engine will overheat and it will boil the coolant, which generates the sweet steam. A broken engine fan, problems with the radiator and even a bad thermostat can also cause this.


What does it mean if the engine starts rattling and the oil light comes on?

Oil starvation is a serious issue that can have its roots in one of several possible conditions. The most likely cause is that the oil level is low, maybe because of an oil leak you'll need to fix.


If a whining sound is coming from the engine compartment as a car is running, what could that be from?

The first thing you should check is the power steering fluid level. If it's low, top it off and keep an eye on it. The power steering pump could be going bad, or the issue might be a belt or pulley.


What does a loud knocking noise while an engine is running possibly indicate?

Explosions happen in your engine all the time, but when they occur before they should the result could be serious damage. Fixing engine knock can include methods like using a different octane fuel, retarding the ignition timing or changing the compression ratio.


What does gray exhaust smoke indicate about a car?

The Positive Crankcase Ventilation (PCV) valve helps release pressure in the crankcase. If the valve becomes stuck, the building pressure leads to oil leaks and gray exhaust. The other possibility is the engine has been burning automatic transmission fluid.


What does a chipped or even split spark plug insulator mean?

The cause of the dreaded spark knock or pre-detonation is usually a faulty EGR valve, clogs in the combustion chamber, timing that's off or overheating.


The oil light flashes irregularly, but only for an instant. What's the reason?

The first thing you should do is check the oil level immediately and top it off. A bad oil pressure sensor is possible, and that's something that should be fixed quickly.


What would cause the heater to stop working suddenly, but air still blows out of the vents?

You might think coolant is something that's only useful in the warmer months, but the fact is the stuff is what powers your heater. Top off the coolant level and your heater should start working just fine again.


What could cause the spark plug electrodes to be broken or flattened?

You always need to double-check that the spark plugs you buy for an engine are actually designed to fit in that engine. If they're too long, they can come into contact with the pistons and cause serious damage.


What causes an engine to idle rough?

Rough idle is often caused by one of the issues already named, as well as issues with the ignition wires, coils, PCV valve, EGR valve, oxygen sensor and even vacuum leaks.


After installing a new battery, the engine keeps stalling. What could be the reason?

The ECU or engine control unit manages all kinds of factors that affect how the engine runs. As the engine ages, the ECU makes adjustments so everything operates smoothly. Replacing the battery might have changed the settings to factory presets, which are great for a brand new vehicle.


Why would an engine idle too high or too low?

Thanks to the complexity of modern engines, a whole range of problems can cause a high or low idle, like an issue with the idle control valve, a vacuum leak, a failed intake gasket or a faulty PCV valve.


If you pull the dipstick out to measure the oil level, and there's a milky white substance clinging to it, what could that mean?

A blown head gasket is the most common reason for this issue, but there are other possibilities, such as a cracked engine block.


What's the origin of a red fluid leaking from the engine compartment?

Manufacturers dye transmission fluid red so it's easy to spot. In some cars, the power steering pump uses transmission fluid, so it could be the source.


What would cause an engine to suddenly lose a significant amount of power?

Your engine needs the proper amount of fuel, or it won't make enough power. If the fuel pump suddenly has problems, you'll notice an immediate difference in performance.


Why would a car start bucking or jerking violently, instead of accelerating and slowing smoothly?

If the throttle position sensor fails in a certain way, it can send a sporadic signal to the ECU, resulting in the bucking or jerking.


What will cause a clear, colorless and odorless liquid to leak under the engine after the car has been parked?

As you run the air conditioning, condensation builds in the system, which then runs out and will pool under the car if it's parked. This isn't a cause for alarm.


If you check the coolant reservoir and there are dark swirls in it, what's the cause?

If everything on your car is running perfectly, the oil and coolant never get close to each other. But, if there's a problem like a blow head gasket, these two fluids can mix, resulting in such weirdness.


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