Lumpy idle

Q I have a problem with my 2011 Volvo C30 D2 with the 1.6 diesel 8v engine – when cold it has a very lumpy idle – when warmed up its fine with no issues. I have changed the fuel filter and its had a service and timing belt kit fitted when I bought it from a used car dealer. There are no lights on the dash and no stored fault codes. Also do Volvo fit a torque limiter to this model as it will not rev out in first gear?

The manual recommend driving off in second gear which seems a bit extreme to me. Willy Paton

Starting with your question on the torque limiter, the engine management systems will limit the engine speed to prevent the engine revving too high when not under load, it will depend of what the engine speed is reaching before it is limited as to whether this is a problem or not.

I have read through the owner’s manual and I am unable to find the section you are referring too that recommends driving off in second gear. I would not recommend this with a standard gearbox and doing so I would expect place a strain on the clutch.

Having changed the fuel filter and serviced the engine, presumably fitting a new air filter as well, it is difficult to say what the lumpiness may be. Any problem with an engine sensor would normally result in the engine management light being illuminated. It would be worth connecting the vehicle up to a diagnostic scanner to ensure that there are no underlying problems, but if nothing can be found then It is possible that a mechanical problem such as a weak injector may be to blame. This may only manifest itself as a problem when cold.

If the problem does continue, it may be worth carrying out a leak-off test on the injectors to ensure that this is not the case. This is done by disconnecting the fuel return pipes from the injectors and blocking off the return hose. Then using four pipes placed into four small bottles with one pipe to connected to the leak-off outlet of each injector, the engine is briefly started and run for around 30 seconds. All four bottles should then contain the same amount of fuel that has bypassed the injector and not been used. If any injector shows a great variation from the others, then this can be deemed to be faulty. A video of a leak-off test being carried out can be seen at this link https://bit.ly/cmqklot