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After replacing the secondary air injection vacuum pipe set it comes with a non return valve (Black & White colour) already fitted in the kit then on start up my 4.2 V8 Petrol revs straight up to 1500 revs when hot, then it dies down straight away to normal tickover about 650-700 rpm.
When started from cold again it revs to 1500 and then straight away drops to 1000 rpm, then as the cold start system switches off its down to normal tickover. The throttle body has been replaced with a new genuine Jaguar one. The engine and gearbox control modules have been re-flashed, but the problen is still there.
Has anyone come across this problem, who may be able to offer any help please.

Hello there,

I think there was an article in the latest JEC magazine about a similar problem. It was not with the X350 but might give some pointers as to where to look.

Hi,
Thanks for your response. Yes I have read the article you mention, and mentioned it to my specialist who does all the work on my car.
Unfortunately the engine system reflash did not cure my problem. I have another X350 4.2 V8 Petrol which I have owned for 15 years
having 74k miles on the clock, and that is perfect. The Secondary air injection pipe set is original on that car. My other 2008 car pipe set went brittle and fell into pieces when removed. The only reason it was replaced was because some guy at a Jaguar main dealership taped up a split without informing me, (Why not replace the set rather than bodging it up) and it was spotted by my specialist who I have used for the last 3 years, so he quite rightly replaced it. (That particular dealership closed down a while ago, I wonder why?)

Anyway thanks for making contact.