Hunting dci

Q I have a 2003 Renault Vel Satis 3.0-litre dci with the V6 Isuzu engine. The car has 90,000 miles on the clock and has been regularly serviced. The water temperature is steady, the engine uses no water and there is no bubbling when the cap is removed. I have been using BP Ultimate and not supermarket fuel. The car is used daily, mainly on short local journeys.

The problem started in the autumn with an intermittent hunting at about 1800rpm when under load. The engine behaves as if starved of fuel. At light throttle on the flat, it happily gets up to motorway speed, but any incline or a need for acceleration to overtake causes it to be strangled. It eventually clears with some white smoke and is right as rain at any speed or throttle setting for the rest of the day. However, it is happening more and more often. Andrew Smith

A Given the symptoms and the fact that the vehicle is regularly used on short journeys, I would suspect the most likely cause of your problems would be the EGR valve. This may simply need cleaning to rectify the problem.

The EGR valve should be removed to clean it properly, although this is not a simple task. Once off, the excess soot can be dislodged before cleaning out the valve with a carb cleaning spray. It is advisable to use new gaskets when replacing the unit.

It is also possible that your symptoms are being caused by the MAF sensor. This may also need cleaning, which can be done using an electrical cleaning spray. When cleaning the MAF sensor it is important not to use a cleaner that will leave a residue, and the sensor must be fully dry when the engine is started.