Uphill struggle

A work colleague who is a bit stubborn has a V-reg Audi A4 1.9 diesel (possibly turbodiesel) that struggles to go up hills, yet runs OK on the flat and gives good mpg. He reckons the injectors need cleaning, but hasn’t done anything about this. I would have thought problem injectors might have caused issues all round, no matter whether the road was flat or hilly. I suggested the rear brakes might be binding, causing more noticeable retardation going up hills but not so noticeable on the flat, but he says definitely not. I guess if the brakes were binding you could tell by the heat and smell.

Every couple of months I travel from Manchester to Tyneside with him in this car and I really don’t want to get stranded!

John Davies

Although the engine struggles on upward climbs, I’m assuming the engine management light has not come on – if it had, your friend might be a little more inclined to remedy the problem! As you have suggested, faulty injectors would tend to cause more problems than are present in this case, one of which would be poor tickover, and a binding brake would result in increased heat and a distinctive smell.

The vehicle should have a turbo and this is one of two possible problem areas. If the turbo were overboosting and putting the engine into ‘limphome’ mode, this would illuminate the EML. However, if the turbo was not operating at all, this would result in poor performance on upward inclines, although there would also be other symptoms, such as oil burning.

The first component I would check is the air mass or air flow meter. This is one of the most common causes of poor performance in diesel vehicles and one which rarely leaves a fault code. If it is faulty, by simply unplugging it for a short run (which will cause the EML to flag up) the difference in performance should normally be felt straight away. This is not a definitive test, but one that will show up the problem 95% of the time.