What Does Car Exhaust Smoke Mean?

Posted: April 30, 2019 By: MattM

How to Interpret the Smoke out of Your Tailpipe

Mechanical issues in your vehicle can be hard to determine without special tools and much like a sick child or pet you may need to work harder to determine if it is just a sniffle or a full blown issue that requires a professional opinion. The smoke from your exhaust can tell you a lot about what may (or may not) be ailing your vehicle and once you know the basics you can pretty quickly tell if it’s something a enthusiast can handle at home.

  1. Black Exhaust Smoke- Generally a black or very dark gray exhaust smoke is caused by excessive fuel being passed through the engine without being fully burnt. This is common on diesel powered vehicles; especially bigger trucks, and also classic cars using a carburetor. During hard acceleration a vehicle may input more fuel and therefore there could be light smoke or a puff on the initial accelaration. If your vehicle is smoking black or a dark gray you may have too much fuel going into the engine and an issue. On classic vehicles make sure the choke isn’t on or stuck or that your fuel settings are correct (float height jet size, etc). If you have a modern vehicle with fuel injection you could have a stuck or faulty fuel injector, a misfire or dead cylinder, or possibly a bad fuel regulator.
  2. Blue Exhaust Smoke- A lighter gray or blueish gray smoke is almost always a sure sign that your engine is burning oil. Engine oil helps lubricate the moving parts internally; but it shouldn’t get into the combustion chamber unless something has gone bad or is wearing out. A common failure on older or high mileage engines is worn/failed piston rings, valve seats, or a failing head gasket. One way to check is to pull your spark plugs and note what each one looks like. If all are dry and a brownish color and one is more black wet it may tell you which cylinder is leaking oil. A light puff of smoke does occur on higher mileage engines during acceleration, but if there is a large amount of smoke when idling or deceleration you may have bigger issues. If you just did an oil change or topped off your oil check your engine oil level as an engine that is overfilled with oil can also cause blow by and oil smoke/burning.
  3. White Exhaust Smoke- When your exhaust is puffing a thick white smoke you surely have a coolant leak into your combustion chamber. This could be caused by a number of things but the most common is a failed head gasket. Other causes could be a warped or cracked head or even a cracked engine block. If your car recently overheated and was acting fine before you could have caused cylinder head or head gasket damage and you may need to replace.

So those are the most common types of smoke you’ll see out of your tailpipes and the reasons that most commonly cause them. If you need the tools and supplies to service your vehicle after seeing excessive engine exhaust smoke you can visit https://www.eastwood.com/

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