Faulty EGR symptoms:

  • Rough idle
  • Loss of engine power
  • Flat spots/ hesitation
  • Engine management light on
  • Blocked DPF

What is EGR (Exhaust gas recirculation)?

EGR is a nitrogen oxide (NOx) emissions reduction technique used in petrol and diesel engines. EGR works by re-circulating a portion of an engine’s exhaust gas back to the engine cylinders. In a petrol engine, this inert exhaust gas reduces the amount of combustible matter in the cylinder, lowering the combustion temperature. In a diesel engine, the exhaust gas also replaces some of the excess oxygen in the pre-combustion mixture. NOx forms primarily when a mixture of nitrogen and oxygen is subjected to high temperature. The lower combustion chamber temperatures caused by EGR reduces the amount of NOx the combustion process generates.

Why do EGR systems fail?

As described earlier, the EGR system redirects a portion of the exhaust gases back into the engine cylinders under certain engine running conditions. This process is controlled by an EGR valve which varies the amount of exhaust gas allowed back into the inlet manifold. These exhaust gases contain carbon, this carbon gets deposited in the workings of the EGR valve and the inlet manifold, and over time can build up and cause issues with the correct operation of the EGR system(stop the EGR valve opening and closing correctly). This problem is far worse in diesel engines due to the higher levels of soot in the exhaust gases.

The EGR valve needs to be closed during the active DPF regeneration process, so a faulty EGR system can cause DPF issues.

EGR cleaning

We can remove the EGR valve and connecting pipe work from the engine and using specialist products, we can clean any build- up of carbon from the system. In most cases this will cure any EGR issues present on most engines. Some EGR valves can cost hundreds of pounds so this process can offer a cost effective solution.

Scroll to Top