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what happens when egr valve goes bad?

All About EGR Delete System-Thinks to know WHAT HAPPENS WHEN EGR VALVE GOES BAD?

This is a long and open-ended discussion about whether to keep or delete the EGR from the engine. First, it is better to understand what the EGR is?

EGR Definition:

EGR stands for Exhaust Gas Recirculation; this system reintroduces some of the exhaust gas into the combustion chamber. When the temperature hits 1600°C Nitrogen Oxide is formed because of the reaction of air molecules, and then Nitrogen N2 and Oxygen O2 present in the air starts to react quickly.

How EGR Works and is it beneficial in Deleting EGR:

With this mechanism some cooled exhaust is added back into the intake chamber, this technique lowers the temperature of the engine and takes it down from 1600°C. The important thing to note is that at the low and full throttle, the EGR system valve is closed and does not permit any exhaust into the chamber.

The discussion is whether it is beneficial or not removing the entire EGR system. And getting rid of it from the ECU will introduce any performance gains or not. There are both schools of thought some speak of performance gain, and some say there won’t be any performance gains. The reality is that there would be performance gains.

The reason is, each combustion chamber can only have a specific capacity. For example, in the case of Ford’s 4.6 V8 engine. Each chamber has .575 liters of space. The first case is, the EGR is not operative, and then all .575 liters of capacity will be occupied with .575 liter of the air and fuel mixture. The second case is, the EGR is operative then all of the .575 liter of capacity will not be occupied with all amounts of the air and fuel mixture as possible.

In the second case, there will be a small amount of capacity occupied by the EGR injected exhaust gasses in the engine. Due to this, removing the EGR system would provide more capacity to burn pure air and fuel mixture that increases performance.

Another thing commonly being pointed out in the discussions is that due to the higher chamber temperature, there will be pre-detonation. This point doesn’t have any supportive arguments because at full throttle the EGR system automatically gets off. At this point of time, the chamber temperatures would be at high levels as compared to when at medium throttle with the EGR system working.

In both cases, with or without EGR, there are some important points to be noted, in the case of removing the EGR, it will become harmful to the environment, but not as harmful as a choked up diesel engine.


A faulty EGR valve can cause problems with the flow and operation of the EGR system leading to performance issues including a reduction in power, reduced acceleration and decreased fuel efficiency. It can also cause vehicle emissions to increase.

On older engines, an EGR valve that is failing to seat properly will result in a rough idle, while one that is failing to open (or has plugged exhaust gas passages) can result in increased engine detonation during part-throttle operation. The EGR systems on newer engines typically have position, pressure and/or temperature sensors that monitor their operation. If abnormal sensor readings are detected the engine control module will illuminate the “Check Engine” light.

Related Reading :LLY EGR DELETE KIT


If it’s stuck open you will notice that you will have driveability issues such as stalling,hard starting & flat spotting when cold or if it’s blocked nothing but an increase in nitrous oxide emissions !If the EGR Valve does not open, the emission test will show higher levels of Nitrogen Oxides, if the EGR Valve is stuck open, the engine will have poor idle quality.

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