The Dane looked set to score his fourth win of the year in the final race at the Nurburgring last weekend, before his third spark plug failure in five rounds this year caused him to drop to fifth. Now, top engineers within VW are set to examine the recurrent electrical problems suffered by Magnussen's Carlin team. As well as Magnussen's three failures, the Dane's team-mates Jack Harvey, Rupert Svendsen-Cook and Jazeman Jaafar have also suffered similar misfires related to spark plug and coil issues. Carlin team boss Trevor Carlin said: "It's not an installation issue, we're doing the same as we've been doing for three years, and the spec of the spark plug hasn't changed - there's no logic to it. "To me, it seems like there's been a batch issue. Spark plugs are very simple, but if you have a small quality issue in a batch it could be causing them to fail. "We've been so good in recent years, this is like a bolt from the blue. It's gone to the very top of VW and Audi now. You expect to have a spark plug fail once every two years, not once every two races."