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Matt
Matt, Mechanical Engineer
Category: Car
Satisfied Customers: 20584
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Problem with my jaguar xf s

Customer Question

Problem with my jaguar xf s
Submitted: 6 months ago.
Category: Car
Expert:  Matt replied 6 months ago.
Hello can you tell me what engine size and fuel type this is please?As I'm assuming its the diesel?
Expert:  Matt replied 6 months ago.
Hello I've seen that you've opened another question and thats not how the site works so keep your replies on this post otherwise you'll be charged per question?I'd first check all the high pressure hoses post turbo/s for any split hoses or cracked metal pipes, also check the ends of the intercooler as its not unheard of to pop the end caps off under high boost. a burst or loose pipe will result in over fuelling and black smoke as you describe If this Ok then it could be a major engine sensor such as the airflow meter or cam position sensor has failed so that the ECU is now overfuelling or injecting at the wrong point and resulting in poor combustion.The quickest route to repair is to have the car plugged into a diagnostic machine which will read off the fault code stored in the ECU and indicate which sensor has failed or whether the fault is more serious. Another possibility is that the fuel filter is blocked so resulting in low fuel pressure and again poor combustion - replace the filter in any case as diesels are very sensitive to this also check how much oil is going through the breather by popping off the intake hose in front of the turbo and checking for oil deposits. Diesels will run off engine oil so this could also be making it rich
Customer: replied 6 months ago.
Hi yep theres no fault code which is strange
Customer: replied 6 months ago.
Also they seem to think that its blocked somewere else and thats why the pressure blew the plenum fitted onto the intercooler
Expert:  Matt replied 6 months ago.
Hello well if the the wastegate is faulty / sticking then it'll overboost and possibly pop the plastic joints on the plenum
Expert:  Matt replied 6 months ago.
check the small vacuum lines to the turbo and its connected control solenoid on the bulkhead, any cracks or leaks can give turbo issues
Customer: replied 6 months ago.
It was a weird one just out the blue no fault codes wont be a blown turbo matt
Expert:  Matt replied 6 months ago.
hello OK if its popped the plenum then it must have overboosted and if a turbo can generate enough boost to pop the plenum then thats a healthy turboso this is why I think its a problem with boost control / wastegate ?
Customer: replied 6 months ago.
I see the car has been mapped as well it didnt actually pop the plenum it cracked the seem what does a wastegate do matt
Expert:  Matt replied 6 months ago.
OK if the car has been mapped then its likely that the tuner is pushing the boost limit outside the normal parameters a wastegate is a separate valve in the turbo to control the level of boost pressure
Customer: replied 6 months ago.
Hi matt not had a problem for 4 months the tuner didnt want to push it to much i could here going from the small turbo to the big turbo like a blow off so what could it be matt

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