Q: Car Loses Power And Puffs Out Large Amounts Of Black And Grey Smoke, First Backfire Was Very Loud, with sulfur/exhaust fumes smell.

asked by on December 22, 2016

2004 Chevy Optra LS

Check engine light was on but went away yet the problem is stll there.... please help is this one of the Catalytic Converters Or?

My car has 287000 miles.
My car has an automatic transmission.

Hello There, This is quite likely a sign of a failing or clogged catalytic converter. The catalytic converter converts toxic exhaust gases into less harmful pollutants that are suitable to be expelled into the atmosphere. When this is clogged, this causes these gases to be backed up into the exhaust system not allowing the engine to breathe properly. This can often times also cause unburnt fuel to be ignited inside the catalytic converter causing either backfire as you describe or in most cases emitting it out the exhaust in the form of black smoke and a very strong fuel smell. When this happens, the engine is forced to work much harder to expel these gases. This often results in the engine bogging down, hesitating, shaking and causing very poor fuel economy. This should also cause a check engine light to come on as the O2 sensors should be reading the incorrect amounts of oxygen in the exhaust gases if this is your problem. I would recommend having an expert from YourMechanic come to your location to diagnose and replace your catalytic converter.

Was this answer helpful?

Hi there. For the engine to backfire, there was a misfire on the engine and the spark plug was fired on the exhaust stroke causing the fuel to burn in the exhaust pipe make a loud bang noise. The black smoke is from fuel and the grey (blue) smoke is from oil. Check the spark plugs and see if they are needing replaced. Check to see if there is a vacuum leak on the engine and if the fuel system is low on pressure. This will make the engine backfire and cause the engine to have a loss of power. If you need further assistance with your engine backfiring, then seek out a professional, such as one from Your Mechanic, to help you.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Need to locate body control module 1998 Chevy Blazer

Hi - on your vehicle, the body control module is located up under the dash, to the left of the brake pedal. Unfortunately, this is not a service YourMechanic can offer at this time. Thanks for thinking of us!

Loud bang from front wheel and the wheel locks up in reverse. It didn't show signs of a bad cv shaft. binding or hub bearing?

Hitting a pothole can damage wheel bearings. Basically, the force of the impact causes the ball bearings to get driven into the bearing race and cause indentations in the race. Then the bearing eventually becomes noisy. You could have damaged...

The clutch pedal has lost all tension what should i check?

The clutch pedal going all the way to the floor without disengaging the clutch is caused by a failure in the hydraulic clutch linkage. There is a clutch master cylinder (and reservoir) and a slave cylinder down underneath near the...

Related articles

Tips for Taking Care of Your Exhaust System
Your Your car’s exhaust system might not be the first thing you think about when it comes to engine performance or personal safety, but it should be pretty high on that list. Your engine combusts fuel and air in order...
Tips for Taking Care of Your Exhaust System
Your Your car’s exhaust system might not be the first thing you think about when it comes to engine performance or personal safety, but it should be pretty high on that list. Your engine combusts fuel and air in order...
The Best Used Cars to Buy If You're an Undercover Cop
If If you're an undercover cop, when you choose a used vehicle, your main purpose is to look like anything but a cop. That means, of course, that an unmarked Crown Victoria is probably not the wisest choice. We’ve...