Who (or what) killed the cat?

The answer from EEC's Stuart Still might surprise you

Who (or what) killed the cat?

Stuart Still, technical training coordinator and regional sales manager at European Exhausts and Catalysts (EEC), on why an emissions test is required after replacing a coil pack.

A great deal of my time is spent diagnosing emission faults and problem solving, some of which could result in a damaged catalytic converter or DPF, even though the faulty component was unrelated and would not normally be associated with a damaged cat.

One of the most effective emissions diagnostic tools is the 4-gas analyser, which by understanding and reading the four gas values correctly, will enable you to locate and rectify many possible faults. Some of these failed components, especially when related to the ignition, could have inadvertently damaged the catalytic converter, even though you would not initially have identified the link, but are often interpreted as an ineffective cat.

When a faulty component has been located, repaired or replaced, it’s important to check that damage has not been caused to a related component.

To enforce this scenario, I was recently contacted by a customer who explained that the Saab 9-5 he was working on had failed its MOT due to the emissions.

He diagnosed the problem as the cat, which was way below its threshold. The 4-gas values backed this up with readings of CO 1.2 percent, CO2 14.3 percent, HC 79ppm, O2 1.2 percent and lambda at 1.04 – these are typical values of a damaged cat that is not working efficiently.

He could not understand this as the car belonged to one of his loyal customers, which is serviced regularly; he had also replaced the catalytic converter just five months earlier due to impact damage, which caused the monolith to collapse.

He was so convinced it was the cat, that he agreed for me to visit him the following day to assist him with his diagnosis; this would give me an opportunity to give the car a once over before he replaced the cat.

It’s extremely unusual for a cat to fail within a two-year period; the ones that do fail are usually associated with an emissions failure or a related faulty component, e.g. EGR valve, air mass meter, injectors, etc.

Arrangements were made for me to visit the garage and examine the Saab. The first thing I checked was the coil pack, knowing that they are a constant problem on Saab 9-5s.

My concerns were correct, as a new coil pack had been fitted three month ago. He agreed that this could have been the source of the problem. We replaced the damaged cat, followed up by a 4-gas emissions test – the results were perfect e.g. CO <0.20, CO2 > 13.5, HC <15ppm, O2 < 0.20 and lambda at 1.

I explained that the damaged cat was a direct result of the failed coil pack, and that it was good practice to carry out a 4-gas emissions test directly after replacing any failed ignition component, especially coil packs.

I was talking to two major auto electrical manufacturers who explained that the UK market for coil packs is immense.

There’s an opportunity for us all to be more effective when repairing customer’s vehicles by reporting possible damaged related component as a consequent of the original problem.

Carrying out this practice will not only reduce catalytic converter problems, it will also help with continued customer satisfaction, by being proactive, thorough and conscientious.

I am convinced that failed coil packs are resulting in a large number of cat warranties. To help reduce this industry problem we have compiled a warning flyer advising that an emissions test is done after replacing a coil pack or ignition related components.

Contact the EEC sales office on 023 9224 53000 or email [email protected].

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