Jaguar XF Diesel Performance Drop: Head Gasket Alert

As someone with some car repair experience, I dealt with very similar symptoms on a 2019 Jaguar XE diesel last year. The symptoms matched exactly, increased fuel consumption, reduced power, and check engine light. Initially, the workshop suspected worn piston rings or head gasket issues. However, after thorough diagnostics, they discovered the root cause was actually damaged fuel injectors. These were faulty due to a previous repair where contaminated fuel had been used during testing. Since the damage was linked to their earlier work, they replaced all fuel injectors at no cost. The repair took about 6 hours, and the engine performance returned to normal immediately. The timing belt was also inspected during this work as a precaution. To help diagnose your specific case, could you share: Current mileage on your XF, Any recent repairs or maintenance, Whether you notice any engine knocking sounds, If there are any blue/white exhaust fumes, When the symptoms first appeared This information would help determine if your issue is similar to what I experienced with the fuel injector system, or if it might be related to other components like the camshaft or cylinder head.

Thanks for looking into this. My XF has 57198 KM on the clock and just had its yearly service last month. I am noticing a slight knocking sound at idle, and there is white smoke occasionally. The symptoms started about 2 weeks after the service. The garage did replace one spark plug during the service since it showed signs of wear. Just got quoted 2500€ for a full diagnostic and potential fuel injector replacement, which seems quite steep. Worth noting that the crankshaft sensor was also changed during that service.

Thanks for those details, this sounds very familiar to what happened with my XE. The timing of your symptoms starting after the service, combined with the white smoke and knocking, points to a potential installation issue with that new spark plug or a problem with the intake manifold seal that might have been disturbed during service. In my case, while the fuel injectors were initially suspected, a second opinion revealed the real culprit was actually a poorly seated spark plug and damaged intake manifold gasket from the previous service. The repair cost was significantly less, around 800€ including parts and labor. That 2500€ quote seems excessive for diagnosis and injector work. Before proceeding, I would strongly recommend: 1. Getting the spark plug installation double-checked 2. Having the intake manifold seals inspected 3. Running a compression test to rule out serious internal issues The white smoke you mentioned could indicate coolant entering the combustion chamber, but given the recent service work, its more likely related to the spark plug or manifold issue. The turbocharger should also be inspected since poor sealing around these components can cause similar symptoms. Would recommend getting a second opinion before authorizing that expensive repair. The symptoms align more with a service-related issue than a major fuel system problem.

Your symptoms starting right after the service work definitely raises some red flags about the recent repairs. Given this information and my mileage being relatively low at 57198 KM, I agree a second opinion makes sense before spending 2500€ on injector work. Will take it to another workshop tomorrow to check the spark plug installation and those intake manifold seals you mentioned. The knocking at idle does seem to match what you described with the poorly seated components after service. Hope its not actually the piston rings or something more serious with the timing belt, since that would mean major engine work. The white smoke has actually gotten a bit worse in the past few days, so will make sure they inspect the turbocharger seals too during the second opinion. Really appreciate the detailed advice, helps rule out some possibilities and gives me specific things to have them check. Will update once I know more about what they find.