October 2021

46 AFTERMARKET OCTOBER 2021 EXHAUST SYSTEM AND DPF www.aftermarketonline.net installed on. The tailpipe emissions are measured and are compared to that of an original catalytic converter. The replacement must also meet any relevant durability, noise and vehicle performance requirements in order to gain approval.” The warning comes following two years of rocketing precious metal prices, as well as a major shift in the government’s approach to environmental issues, with plans now in place to cut carbon emissions by 78% by 2035. Toby continued: “Rhodium is a key component in petrol catalytic converters for reducing harmful vehicle emissions, particularly Nitrogen Oxides (NOx), which are produced in any combustion process.Without doubt it’s a complicated issue. Poor quality catalytic converters can still pass a MOT and mistakes can happen through the entire supply chain. Legislatively, it’s very complex and this brings about exploitation of the rules and unfair competitive advantages, but the issue won’t go away. It’s essential we raise standards to ensure the aftermarket is playing its part in reducing harmful emissions and air pollution.” Increased demand Looking back at today, Autumn 2021 is proving to be a busy time for workshops as they deal with increased demand for MOTs, with thousands failing on exhaust emissions leading to increased demand for the replacement of Lambda sensors. Mark Hallam, Marketing Manager, NGK Spark Plugs, observed: “A worn or failed sensor can result in drastically reduced control of the fuelling system which could result in increased fuel consumption, uneven running, generally poor performance or failure of a MOT emission test.” NGK also recommends that the function of the sensor is checked every 20,000 miles or annually. “A malfunction of an associated part may directly affect the performance of a sensor, “observed Mark. “An oscilloscope and gas analyser is a much more accurate way of assessing sensor performance than relying on fault codes alone. Garages need to look for slow response times, output range and heater function. Contaminants from poor quality oils and fuel which remain in the exhaust gases can become deposited on the sensor element affecting its operation. Even coolant from a leaking head gasket can reach the element.” Positioning On identifying sensors, Mark commented: “Lambda sensor positioning in the exhaust system has many descriptions throughout the automotive industry, which can differ from that read on fault diagnosis equipment. For ‘sensor 1’ it is also known as regulating, front, upstream, pre-cat or upper. For ‘sensor 2’ they can be referred to by some as diagnostic, rear, downstream, post-cat or lower. "As a manufacturer, NGK is often quizzed; ‘the garage has asked for ‘which one do I supply?’ To aid factor selection and correct supply first time, a fault code relating to ‘sensor 1’ and ‘sensor 2’ are commonly referred to on the factors’ parts look-up systems as ‘front’ and ‘rear’ respectively. Referring to them as such can avoid delay and ensure correct supply first time in the event of a member of factor staff being uncertain.” EGTS Moving onto exhaust gas temperature sensors (EGTS), Mark said: “EGTS have become commonplace in modern engines for petrol as well as diesel. They are used by vehicles mainly to prevent over-heating of components within the exhaust system, often during regen cycles. For this reason, their position is often described on parts systems for the component they are protecting, e.g., Pre-Turbo, Pre-DPF etc. Sensor position displayed via fault code is unlikely to be sufficient for a factor to select the correct sensor. When requesting a replacement EGTS, always check carefully which one is required, there are very often more than one fitted, and exactly where it is installed into the exhaust system e.g., in relation to turbo, cats, DPF, NOx trap, and ensure this information is passed on to the factor.” EGR Commenting on exhaust gas recirculation (EGR) valve problems seen on common TDI applications, Nissens Marketing Manager Jan Zieleskiewicz said: “The EGR valve used in multiple VAG diesel applications utilising the 1.4, 1.6 and 2.0-litre TDI units can be particularly problematic, as it is especially susceptible to heat and vibration, as well as excessive engine load. Naturally, the faulty valve has to be replaced because its failure will impair the function of the entire exhaust emissions system, so affecting the engine's proper operation. However, as the issues are largely due to the design of the original part, workshops must be aware that these malfunctions can occur both in the original, and a replacement part. “Common signs of EGR valve malfunction include engine check control lighting on the dashboard, the ECU setting the engine into limp mode, reduced engine power and significant changes in fuel consumption. There is also likely to be pinging and knocking sounds emitting from the engine, rough, uneven idling. Stalling and hesitation during acceleration is also likely, along with exhaust gases escaping within the engine compartment.” Jan continued: “Fortunately, the Nissens Efficiency & Emissions division has stepped in to provide a solution to Right: NGK Lambda sensor LLeft: NGK exhaust gas temperature sensors (EGTS)