Hesitation under load

I’m having trouble with a 2007 Land Rover Discovery 2.7 TDV6 and wondered if you can help. It hesitates under load and sometimes goes into limp-home mode. The EML is on and codes P0490 and P045D are stored. Foxwell NT301 says these are ‘Exhaust gas recirculation control circuit A high’ and ‘Exhaust gas recirculation B control circuit high’.

Do you think this indicates failure of both EGR valves? I’m assuming that they are probably stuck due to carbon build-up and wondered if there is any way they can be cleaned in-situ because valve removal is difficult due to restricted access.

I’m happy to remove and try to clean them before replacing them – I’ve successfully stripped and cleaned one from a Renault Espace. I also realise the issue could also be burnt-out actuators, in which case they will have to be renewed. I could check this in-situ if I knew the connections. What are your thoughts on cleaning EGR valves generally? Any help would be gratefully received! Andrew Green The codes P0490 (Exhaust gas recirculation [EGR] system – circuit high) and P045D (Exhaust gas recirculation [EGR] valve actuator B – circuit high) do of course point to a possible EGR valve problem, but the fault could also be with the wiring to the actuators. I would carefully check the loom to ensure that no breaks in the wire are present.

Using an ohmmeter, the actuators can be checked by bridging pins 3 and 4 of the component plug: you should get a resistance of around 4 ohms. Autodata informs me the wire colours going to these pins are green/blue and white and black. If the readings are good, it can be assumed that the actuators are good, but it’s possible the valves are sticking. In this case cleaning would be a worthwhile option.

Cleaning in-situ is a compromise – but may achieve the results required. I would normally try a cleaning spray such as this one http://bit.ly/cm3legr

By disconnecting the EGR pipes to the block, you can then spray into the valve without too much dismantling and should be able to free the valve off if stuck through carbon deposits.