Sure, on a cool morning your exhaust might make a little steam, but when it’s smoke coming out of your tailpipe, you need to find out why.

Exhaust Smoke: Troubleshooting by Color

Exhaust smoke generally occurs in one of three colors.  The exhaust smoke will either be black, white or blue.  The color of the smoke being emitted from your exhaust actually tells quite a bit.

Black Exhaust Smoke

If you drive an older diesel vehicle, you already know that some black smoke when you first start it up isn’t anything out of the norm.  On the other hand, if you have a gasoline powered engine, black smoke is a red flag.  This color usually indicates that the air and fuel mixture isn’t right.  This can be caused by a leaking fuel injector, getting too high fuel pressure, possibly a clogged air filter, and if you have an older model engine with a carburetor, your automatic choke may be stuck.

White Exhaust Smoke

White smoke billowing from a tailpipe means your engine is burning either the coolant or transmission fluid.  Neither of these is good.  This likely means your head gasket is leaking or your cylinder head is cracked.  If it is transmission fluid causing the smoke, your engine is pulling the transmission fluid in through a vacuum hose that goes to your transmission.

Blue Exhaust Smoke

Blue smoke means your engine is burning oil.  There are a few culprits that are usually behind burning oil.  You may be dealing with damaged or worn cylinders, broken or worn piston rings, or a faulty valve or bad valve guide seal.

Exhaust Smoke: Troubleshooting by Smell

Black smoke issues do not always have a strong enough smell to really perceive and describe.  If you’re having black smoke, I’d suggest you check the automatic choke if you have one.  If your car is one with the newer type with fuel injection, you should check your fuel pressure.  Again, a clogged air filter can be to blame, be sure you inspect the air filter.  If it is dirty, changing your auto air filter is pretty easy with these basic instructions.

White smoke coupled with a smell that is slightly sweet usually indicated coolant burning.  If your vehicle has been overheating along with this white exhaust issue, I suggest doing a pressure test on your cooling system.  You want to determine if the system holds pressure properly. If you find that it does not, you are possibly dealing with a leaking head gasket.  If this is your problem, the head gasket will need to be replaced.  You should also check your coolant levels to see if it looks low.

White smoke with a general burning scent is more likely attributed to transmission fluid burning.  Start by checking your transmission fluid level.  If the level is low, you need to add the manufacturer recommended type of transmission fluid.  Only add enough to bring it back up to full. You will also want to inspect the vacuum hose running from your transmission for any fluid inside. If the vacuum hose is passing fluid through it, you will need to replace the vacuum modulator valve on the transmission.

If you’re seeing blue smoke, you probably smell something along the lines of a bitter, burnt toast type of scent.  This is because of the burning oil in the engine.  Start with checking you oil level and refilling it as needed.  You should be vigilant in checking the oil until you rectify your problem.  If you do not take care to make sure oil levels are not dropping too low you will end up with a much bigger, more serious problem than you have right now.  At this point you may want to perform a compression check (also referred to as a leak down test) to help in diagnosing bad pistons or rings.

Possible Auto Repair Solutions

As you can see, the repair you need will depend on all of the information above.  Let me attempt to give you an idea of what each might involve.  Black smoke issues will usually be solved by adjusting the choke, replacing an air filter, leaking fuel injector, or faulty pressure regulator.  If burning coolant is the problem, the cylinder head will be coming off in order to replace your head gasket.  Burning oil will likely need an engine overhaul to replace rings and valve guide seals.

To set an appointment at our auto repair shop in Columbia, SC call (803) 735 – 7902.