Fig 1.

A buffet of errors

We hope you brought your appetite with you this month, as Frank has laid on a veritable feast of technical issues for you to chew through

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Published:  06 November, 2020

I have always focused on topics that have developed through our workshop, the main reason for this is authenticity and integrity. However, it is not always possible to be fortunate enough to have topics with enough content for publication. So, this month we are going to have a banquet of multiple stories of interest where you can spin the table and pick your favourites.

First topic
An Audi S3 came in for a MIL light and poor running complaints. Initial serial interrogation concluded camshaft correlation errors. This has significant concerns with this 888 power plant, as it has variable inlet and exhaust control as well as exhaust valve lift. This is a very powerful and usually competent engine, but unfortunately the vehicle was purchased recently with a known poor service history. This is an absolute no-no with today’s technology. Having conducted a basic health assessment, and noting actual and specified camshaft position errors, it was decided to replace the oil and filter. I must add here that it ran much worse afterwards.

Historical experience has shown problems with chain jumping and oil filter cartridge collapse. This engine employs a variable displacement oil pump providing 1.8 bar at low speed and 3.8 at higher load. It is also PCM-mapped. I am not a fan of such a low oil pressure especially on crank start. My Seat Cupra has on several occasions displayed slight chain tension noise on start up. Bear in mind I replace the oil every 3,000 miles, and it has only done 18,000 miles.

Additional thoughts should be given to Stop/Start; All engines will suffer gravitational oil drainage when stopped. We are now increasing this multiple times. Not a good idea really. We have also seen oil filters collapse shedding filtration media particles into the oil galleries.

The timing cover was removed, visual evidence shows surface bearing damage to both the cams and alloy cover. This evidence confirms both a boundary layer lubrication failure and metallic swarf erosion. In my opinion this is sufficient evidence to reject the entire engine, subject to a total strip-down. Please refer to; Fig.1, cam sprocket and chain; Fig.2 cover housing; Fig.3 Parts assembly.
The vehicle is still enjoying an elevated position awaiting my report for the insurance company, which requested to know what caused the problem.

I have penned many reports and have prevailed in all my expert witness cases, and smell another one here, or it could be the beef noodles and bean sprouts?

Second topic
Next, we have an AUDI A6 2.7 CRD presented to us as a trade-in into a Vauxhall dealership. The problem is that it is cranking with intermittent no-start. Initial checks were carried out showing a DTC, ground short to power on the in-tank fuel pump relay. I am often amused with this description, as if it  was taken literally there would be smoke and probably fire as the loom fuses together rather quickly.

Please refer to Fig.4 relay location r/h. Time to call Diagnostic David. Why the definition? Well, we have three Davids at ADS. Diagnostic David bridged the relay 30-87 terminals in order to run the pump and the vehicle started every time. He then conducted wiring integrity tests between the PCM and pump relay focusing on terminals 86-85. No problems here, power was present from supply right back to the ground control circuit at the PCM. The obvious conclusion an internal PCM ground switch error? This is where you MUST take a pause? Why? Because you have discovered the symptoms NOT the cause. David then exposed the edge connector between the loom and PCM. Please refer to Fig.5; Oil on PCM socket. David elected to expose the board in the PCM and visually check for component damage. Visual evidence shows blister damage to a controller chip suggesting excessive load.

Having discovered oil on the edge connector we now need to prove the cause. So, we are looking for capillary invasion through the loom from a component with access to oil. The usual and obvious components oil switches showed no oil invasion on the sockets.
In fact, the search proved difficult due to limited access. However, David eventually discovered the path of capillary invasion back to #5-injector socket. This engine variant uses piezo injectors, and to my knowledge I have never heard of or experienced this type of problem. The electrical connector is external from any lubricant, so the problem must be internal from within the portion that is exposed to lubricant.

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