Symptoms

At first the symptoms were simply that the dashboard MIL would light and then go out. However as time went by the performance of the car became worse.

• Fuel consumption began to drop
• Smoke was generated on acceleration
• Throttle lag
• Excessive diesel knock.
• A slight misfire similar to a spark plug needing replacement (of course it's a diesel)

These symptoms would come and go as if controlled by a switch. For periods the car would be completely normal and then for no obvious reason start. Most noticeably this would be on a motorway drive.