www.jec.org.uk

I've recently had a bit of a panic on. I got the dreaded "Restricted Performance" warning (again!) and managed to get home. The car had stored a fault code P0299 Turbocharger Underboost and I feared the worst!

However I called the AA and they very quickly heard/spotted a hissing noise. This was found to be a split hose on the waste gate actuator between the two turbos (240PS twin-turbo 2 litre Ingenium diesel). The split was in a right-angled rubber section of the 5mm I/D vacuum pipe that pushes onto the actuator. Problem solved - they chopped 20mm off the end and away we go. There is no part number on the 3" piece of 90 degree rubber tube, just manufacture date. So I rang the dealership - £355 for the whole assembly of vacuum pipes (rigid plastic and rubber) so I don't think I'll bother. I've ordered a metre of vacuum hose from Amazon so if I'm stuck again I've got backup. The AA recommended that I get the right part, as a straight section bent to fit might collapse with the vacuum. However, as its not available, I've got some good quality flexible pipe that I'm sure will work fine, at least for a quick fix.

Lesson learned - don't panic, it might not be a disaster!

Interesting - did you notice any reduction in power before the 'limp home mode' kicked in?

Kind regards
Paul

Paul Russell
SUV Coordinator
Jaguar Enthusiasts’ Club

I don't think I did notice any power loss. But if it was gradual then I may not have.
The 250 has oodles of it that I don't normally use - I'm always watching the MPG so I tend not to use the extra unless I need it e.g. when towing.

The AA patrol said that the EEC was reporting failure to achieve the required boost, so it sounds like the system detected the lack of boost that it would expect at that demand level. Depending on how sensitive the trip level is, it may well have been achieving the required boost until it was not. I'm guessing the split in the pipe didn't happen all at once, but progressed until it was big enough to trip the detection system.

I bought a metre of 5mm silicon vacuum pipe from AP Racing, and it is noticeably thicker on the pipe wall - more robust than the OEM pipe. But I haven't fitted any until I need it.