{"id":4528,"date":"2023-07-21T16:14:45","date_gmt":"2023-07-21T16:14:45","guid":{"rendered":"https:\/\/carcarecamp.com\/?p=4528"},"modified":"2022-05-07T16:16:22","modified_gmt":"2022-05-07T16:16:22","slug":"can-exhaust-leak-cause-rough-idle","status":"publish","type":"post","link":"https:\/\/carcarecamp.com\/automotive-info\/can-exhaust-leak-cause-rough-idle\/","title":{"rendered":"Can Exhaust Leak Cause Rough Idle? \u2013 Everything You Need to Know"},"content":{"rendered":"\n

Internal Combustion engines are finicky machines.<\/p>\n\n\n\n

Engines need just the right amount of fuel, air, and spark at just the right time for them to be happy and run smooth. However, if either one is missing, incorrect, or unaccounted for by the Engine Control Unit (ECU), then the engine will start to run rough \u2013 especially at idle.<\/strong><\/p>\n\n\n\n

Now, you\u2019ve probably heard that exhaust leaks can cause all kinds of problems<\/a>, but can exhaust leaks cause rough idle?<\/p>\n\n\n\n

Also Read:<\/strong> How To Get Exhaust Popping Sound (Without Tune)<\/a><\/em><\/p>\n\n\n\n

Can Exhaust Leak Cause Rough Idle?<\/strong><\/h2>\n\n\n\n

An exhaust leak can definitely cause rough idle if the leak is located before the upstream O2 sensor or very close to it. <\/strong>The exhaust leak will set off a false lean condition, to which the ECU responds by increasing fuel delivery. This results in an Air-To-Fuel mixture that\u2019s way too rich and thus causes the engine to misfire and\/or run rough at idle.<\/p>\n\n\n\n

The most common places for an exhaust leak to occur before the upstream O2 sensor are the exhaust manifold, exhaust manifold gasket, downpipe, downpipe gaskets, and the flex pipe.<\/p>\n\n\n\n

Why Do Exhaust Leaks Cause Rough Idle?<\/strong><\/h3>\n\n\n\n

Ever since fuel injection was invented in the 80s, all engines using it were fitted with a bunch of sensors that monitor the exact amount of air going to the combustion chamber, and the amount of air leaving the engine through the exhaust. It was necessary in order to precisely calculate the exact amount of fuel that needs to be sprayed into the combustion chamber, otherwise, the engine will not run right or at all.<\/p>\n\n\n\n

\"O2
O2 Sensor. Photo by Ferrous B\u00fcller<\/a>.<\/em><\/figcaption><\/figure><\/div>\n\n\n\n

The inlet air is measured by either the Mass Air Flow sensor, Intake Temperature Sensor, the Manifold Absolute Pressure sensor, or a combination of all three, while the exhaust gases are measured by the upstream O2 sensor, which determines whether the engine is running lean or rich by measuring the amount of oxygen in the exhaust system. More oxygen means that the engine is running lean and less oxygen means that the engine is running rich.<\/p>\n\n\n\n

Now, the exhaust system is completely sealed from the outside air, but if fresh outside air gets inside through an exhaust leak somewhere upstream of the O2 sensor, then the sensor will detect that there\u2019s too much oxygen in the exhaust. The O2 sensor cannot tell whether it\u2019s due to an exhaust leak or a poor Air-to-Fuel mixture, therefore it just sends the information to the ECU.<\/strong><\/p>\n\n\n\n

The ECU responds by richening the fuel mixture, even though the mixture is fine in reality. This causes the engine to run very rich, which in turn fouls the spark plugs and makes the engine run rough at idle.<\/strong><\/p>\n\n\n\n

Also Read: <\/em><\/strong>Can an Exhaust Leak Cause Loss of Power?<\/em><\/a><\/p>\n\n\n\n

Can an Exhaust Leak Cause Damage to Anything?<\/strong><\/h2>\n\n\n\n

An exhaust leak can and likely will damage your exhaust system components if it causes the engine to run rough and misfire.<\/strong><\/p>\n\n\n\n

If an exhaust leak is bad enough, then the upstream O2 sensor will be falsely reading a lean condition, even though the engine is running fine. This will force the ECU to add more fuel in order to compensate for the false lean condition.<\/p>\n\n\n\n

\"Bad
Bad Catalytic Converter<\/em><\/figcaption><\/figure><\/div>\n\n\n\n

Now, once the engine starts dumping a lot of unnecessary fuel into the combustion chamber, a bunch of unburnt fuel will escape through the exhaust valves and into the exhaust pipe. The unburnt fuel will then get in contact with hot exhaust components and ignite, causing a lot of damage to the exhaust piping and especially the catalytic converter.<\/p>\n\n\n\n

If you suspect that your car has an exhaust leak and it even started running rough at idle and misfiring from it \u2013 get it fixed ASAP!<\/strong> Continuing to drive will cause more damage and lead to very costly repairs.<\/p>\n\n\n\n

How To Locate an Exhaust Leak<\/strong><\/h2>\n\n\n\n

The only places for an exhaust leak to occur before the upstream O2 sensor are the exhaust manifold, exhaust manifold gasket, downpipe, downpipe gaskets, and the flex pipe. That is, at least on most cars.<\/p>\n\n\n\n

Different make and model vehicles have different exhaust system designs. On some cars, the upstream O2 sensor is located on the downpipe, others have the O2 on the catalytic converter, and some models even have the O2 on the exhaust manifold.<\/p>\n\n\n\n

1. Check The Exhaust Manifold for Leaks<\/strong><\/h3>\n\n\n\n

The exhaust manifold can only leak from three areas \u2013 the mounting surface gasket (between the engine and the manifold), the downpipe\/turbo gasket, or the manifold itself can crack.<\/p>\n\n\n\n

Exhaust manifold leaks make a really distinct ticking sound<\/strong> that closely resembles the sound of a noisy valvetrain.<\/p>\n\n\n\n

Now, a bunch of engines, like the 5.7 Hemi, are notorious for broken exhaust manifold studs and loose bolts. This usually happens due to poor exhaust manifold design and constant heat and cooling cycles. That\u2019s probably where you should check first.<\/p>\n\n\n\n

\"Exhaust
Exhaust Manifold Bolts<\/em><\/figcaption><\/figure><\/div>\n\n\n\n

You can try tightening the exhaust manifold bolts just a bit to see if they aren\u2019t loose. If they\u2019re tight, give the exhaust manifold a visual check. Look for cracks and soot marks.<\/p>\n\n\n\n

If the manifold looks fine, then the last thing to check is the gaskets. You can usually tell that they\u2019re blown and leaking by looking out for black soot that accumulates around the leak area.<\/p>\n\n\n\n

\n