February 2021

BY Frank Massey I have always attempted to present topics that vary in subject and technical challenge. This month’s subject delivers on all counts. A unique problem which challenges over vehicle knowledge, process and patience. In fact, it was so complex, this month’s topic almost ran in real time with publication. A story from my many years of cycling in Europe will, I hope, illustrate my involvement with this diagnosis process. Several years ago, cycling from Paris to Pisa we had to divert from Grenoble to Marseille by train due to the Alps closed by heavy snow. Why should I have been caught out in this way? Well, it was May! Our onward journey took us to Ventimiglia. On this journey we watched in amusement as some people kept boarding and leaving the train playing cat and mouse with the ticket collectors. This very accurately describes my involvement in the diagnostic process with an AUDI S3, it also reminds me of an old expression; ‘Two many cooks in the kitchen’. It also reminded me of an old army adage; ‘Never share command!’ Causes The vehicle presented many potential causes for what initially seemed a straightforward problem. It was booked in for a catalyst efficiency error, where a failed and partially restricted catalyst was discovered. This model variant utilises the brilliant EN888 engine which produces around 300BHP out of the box. This is a power plant I know very well due to my previous research and authoring in past technical topics. It is also fitted in my SEAT Cupra. Like the song says, “when the going gets tough, the tough get going,” and I was the go-to tough guy. Where’s Billy Ocean when you need him? Having removed the catalyst substrate, temporarily, It was noted that an intermittent misfire count was present on #1 cylinder. At this point I’m going to sound like a parrot; Misfire can and should be described more accurately as a combustion anomaly, the cause of which can be one of three possibilities; Fuelling, ignition, or mechanical malfunction. Somewhere in the mix of the repair process, responsibilities were split between three techs. This is something I do not agree with, but accept it can occur due to staff holidays which I think was the case here. Attention was first paid to the ignition, new spark plugs, and coils were exchanged. Result, no change. The intermittent combustion continued both on and off-load with a prevalence for #1 cylinder. Process I was not involved with the diagnostic process at this point, but a decision was taken to remove both sets of injectors for ASNU test bench assessment. I did witness the results found by Peter B, which convinced me the fault lay 22 AFTERMARKET FEBRUARY 2021 TECHNICAL www.aftermarketonline.net SETTING THE BAR HIGH Frank’s recent struggles with an Audi S3 is a tale for the ages, and it nearly took him as long to get a grip on the problem elsewhere. The intake swirl flaps were cleaned and tested for smooth movement transition. David M decided to replace #1 high pressure injector which also muddied the waters. With the fault still present and apparently getting worse, the vehicle would start promptly then descend into a severe combustion malfunction this lasted for several minutes, then apparently smoothing out. However, under dynamic road test a combustion count was predominant on #1 cylinder but did display similar events on multiple cylinders. A serial data logs clearly identified a cylinder misfire count synchronised with a drop in high fuel pressure. Nominal fuel pressure during warm up is around 60 bar, this was reduced to around 35 bar with the immediate effect of increasing the misfire count. So, the problem was fuel supply related. David M took the decision to replace the high-pressure pump, believing the fault was a high- pressure pump problem. This did not have any effect whatsoever. Advice At this point I was asked to review the diagnostic process and provide advice, this is where I recalled jumping on and off the train with no fare in my pocket. My reputation was very much pinned on my passion for the application of oscilloscope evaluation, and still is. However, serial data is essential for capturing information. It is quick and provides the actual sensor values at the PCM and any correction values. I was updated as to the previous tests carried out to the PART ONE Fig 1: EN888 engine