EGR removal must be carried out correctly to avoid problems

Exhaust gas recirculation (EGR) systems are notorious for developing faults on older or high-mileage vehicles and when correctly carried out, EGR removal is a relatively straightforward procedure that can resolve problems once and for all. Even on vehicles that are functioning correctly, EGR removal can often increase performance and benefit economy, with no downsides whatsoever. However, the important phrase is: 'when carried out correctly'.

We have heard about and have come across a number of examples of vehicles where EGR removal has been carried out incorrectly. In these cases one of two methods has nearly always been used. First, the physical parts of the system have been removed or bypassed, but the electronic engine management systems have not been correctly reprogrammed at best, or at worst are simply either ignored or tampered with. In one instance we are aware of, the warning light for the system was simply disconnected and a valve linkage removed. Second, the engine management system is partially reprogrammed to simply preventing the EGR valve functioning, but without making any changes to fuel injection and ignition timing settings. These are part of the engine 'map' in electronic control systems and must be correctly set.

These methods are relatively quick to carry out and correspondingly do not cost a great deal. However, both will result in poor running and most likely worse economy. More importantly, in the long term, serious engine damage is more than possible. Further, a vehicle with its EGR system incorrectly removed may well not meet relevant standards for exhaust emissions and may consequently fail its next MOT test.

The ECU, or electronic control unit, is a complex computer with highly detailed programming. It regulates various engine functions on modern vehicles, including the ignition timing and fuel injection, in order to assure best possible running under all circumstances. If your vehicle was fitted with an EGR system from new, then the ECU will have been programmed to monitor the system and provide fuel injection and ignition timing in line with the operation of the system, and all other associated systems. When carrying out EGR removal properly, the parameters for engine management must be correctly reprogrammed in order for the engine to operate at its optimum efficiency as well as changes to the software to delete the EGR functions. Failure to do this will at best result in poor running, and/or an actual decrease in performance and economy. At worst, significant engine damage could result. Unless programmed correctly, the engine management system will assume that a percentage of exhaust gas is still being fed back into the engine and will adjust fuel injection and timing accordingly.

At MK T and B Centre, we have all the correct equipment and programming software to ensure that EGR removal is carried out correctly and that the vehicle's ECU is re-programmed to ensure correct running. This will ensure performance and economy are maintained, without compromising reliability in any way.

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