Thursday, November 29, 2012

Car Backfires

Causes and reasons for vehicle backfire

  • When excessive fuel in the exhaust hits a hot catalytic converter the engine backfires.
  • The spark occurring when the exhaust valve is open causes ignition backfire.
  • Combustion occurs when intake valve is open,vehicle backfires.
  • Leak in intake and exhaust manifold also causes backfire.

Actually what happens is when inlet valve and the exhaust valve are both partially open at the same time, un-burnt fuel escapes and get enter into the exhaust manifold. This ignites, causing a backfire.


Mostly on backfire issue you will noise a flame coming out from exhaust pipe.And also a heavy loud spark noise from same area.

Its like something got stuck up in the lines and to clear the clog,the engine backfires.

The vehicle will loose power and will won't run in forward direction.
Or will run but make loud noise.


Backfire results due to malfunctions related to the air to fuel ratio.
On both engine models you will notice back fire.
Fuel oriented and carb oriented.
If a engine running lean backfire will be noticed on  carbureted engines.
It occurs due to the air-fuel mixture has insufficient fuel or whenever the timing is too advanced. 

There is one stage where the actual backfire is no caused, and you notice a MISFIRE. These stage is called as incomplete combustion.
What actually happens in incomplete combustion is engine runs leaner or if there is less time for the fuel to burn in the combustion chamber. The condition that causes this is a misfire. 
These misfire creates chances of backfire.
Now when misfire occurs the unburned fuel or flammable hydrocarbons are delivered to the exhaust manifold where they may ignite unpredictably. And you notice backfire from engine.

Sometimes backfire is noticed  when the engine is running rich (with excess fuel) and there is incomplete combustion and same misfire gets created and that too results in bacfire.



Exhaust system backfires issues :----


  • Engine with emission system malfunction causes backfire.
Emission system malfunctions   
  • Air injection system diverter valve problem
  • Or it can be an exhaust leak.
  • Or on some cases when the catalytic converter has removed. 


Now on  high-performance vehicles:-----


When the vehicle gears are shifted up and accelerator is left off, at that time  the engine has a moment of running rich.Now due to the vehicle running rich overfuel gets entered into system.Due to these more then required fuel  incomplete burn of fuel occurs and this causes the fumes to explode in the exhaust system and also popping sound is heard. 

Fuel-injected engine backfire:-----

The engine may backfire if an intake leak is present.The intake leak causing the engine to run lean.
Also if  air-flow sensor is defective the engine runs lean.Due to lack of required fuel the backfire issues are noticed.
The fuel proportion should be exactly same as required,not less or not much.
So as air flow sensor being fuel injection component,if its faulty you notice the engine backfire issues.


The Very Common causes of  Engine backfires are:

Poor engine timing  cause intake backfires and also exhaust backfires
Ignition wiring misaligned lead to timing issues and timing issues lead to backfires

Fuel pressure getting very low causes backfire.
Fuel filter worn out clogged with dust causes backfire.
A fuel pump when gets old,it will not let the fuel to run as per required flow,these also causes back fires.  A lean air-to-fuel ratio during fuel injection causes backfire
A faulty catalytic converter can result in backfires out the exhaust tailpipe.


So as you can majorly see the issue with fuel system,air filter and catalytic converter causes most of the engine backfire issues.Backfires can occur when car not tuned properly for the application as well as just having mechanical valve failure.
If the valve timing is thrown off or the valves not seating properly .These cause fuel  push back up past the intake valve during ignition. While there can be more things that cause a backfire, these are just a few.

Getting your vehicle properly serviced on time and engine tune up done regularly as recommended by service manual helps to keep your vehicle trouble-free.


These details will help.
Thanks.


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