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What oil do you use? When was it last changed? I was thinking this could be linked to a faulty camshaft sensor but gave AI a go and here's it what it suggested
I use Mobil 1 5W/20. I changed the oil last time at 67,000 miles, so 8,000 miles ago and almost a year ago. I topped the oil off about 2 months ago.
The last Blackstone report from Dec 2024 said everything looked pretty clean from the oil sample.
The low engine oil light was not illuminated on the dash. I measure the oil levels using torque pro app, and everything looked within the same range I’ve been getting over the past year of measurements.
It's hard to tell as I don't know enough about your reman engine. I put in a JLR factory remanufactured engine this year at 34K miles after a big end bearing failure. The repair was mostly covered by my 3rd party warranty.
I pushed the car hard in first gear at a mildly inclined junction and my thinking is that the oil pump crapped itself starving the bottom of the engine of oil for a short time and the bearing snapped.
The replacement JLR engine is all brand new except for the sump and it's been solid so far. It's got 2 years warranty unlimited mileage. I replaced the oil at 1K miles and will be changing it at 3K intervals, 0w20.
I'd be looking to speak to whoever fitted the new engine to see what they think especially if you have any warranty left. The easiest thing to do would be to clear the codes, check your battery health, remove and inspect the oil filter. All being well, replace the oil. If it's still running rough, work through the list in the link shared above.
What oil do you use? When was it last changed? I was thinking this could be linked to a faulty camshaft sensor but gave AI a go and here's it what it suggested
ChatGPT speaks with such confidence even while misleading all who listen. Please look a bit closer to see how these platforms operate. The list of advice is really what most people think makes sense to them, so they polluted the internet with their ideas which sound good but lack basis. The LLMs search, collect, and present in a new and clever way. Yet, all this is still equivalent to asking everyone at your kid's ballgame to diagnose a lump in your neck.
I gave it a try,I got a long narrative that failed fundamental logic. Let's check the advice it sent here. It suggested 3 of 4 VVTs all mechanically failed at the same moment in time. These VVTs then followed up by "triggering" the low fuel pressure codes on the fuel rails. There's no way all those units mechanically failed in unison, also conspiring to throw the same codes. CGPT could have easily not mentioned all this, because it can't happen, but keep in mind its not intelligent, either artificial or real. It can only regurgitate info from internet searches. No, these VVTs stopped working due to a failure higher in the architecture which handles all 4. The VVTs did not all get stuck, nor the solenoids or valves all just quit together, kinda like going on strike. Whenever multiple subsystems quite together, I go upstream looking for a module in common the subsystems depend upon. The same issue strikes off this list cam chains, tensioners, guides and all. Cam drive troubles hit cams in both banks with separate drive systems, at the same moment.
Now for the High-Pressure fuel system. The CGPT just list every single thing from the internet which mentioned fuel. This code P00C6, cannot be set unless the starter is engaged. CGPT cannot use logic to show this error. Perhaps the code is historic, or maybe you tried to start it before you pulled the codes. If historic, it would not be included in this failure scenario. This HP fuel system is remarkable in many ways. The fuel tank has two pumps to handle the saddle tank issue, and a common controller between them. If any of the 3 would have had a problem, there would be a code reporting that system, not the high-pressure system. There are two HP mechanical fuel pumps which are engine driven. The fuel rail pressure is variable. Max pressure is150 ATM, and it is used often. Techs would not try to measure that pressure when it's so easy to get from the ECM which also proves the pressure sensors. Our engine controllers have specific limp mode features which limit maximum RPM, it does not have a way to limit fuel delivery. There are a few different RPM limits depending on the level of risk to the engine. There are many failures which cause rough running, most do not also trigger a limp mode. I'm surprised the controller didn't shut this car down.
CGPT uses the shotgun diagnosis method. So, about 10% of the comments are worth the effort.
Your CATs might fine. If that code is new, it's possible it was triggered by this event, but very unlikely. That code doesn't turn the MIL on until the system measures the exhaust over the limits 2 consecutive operations. So, a single exposure cannot alone cause that DTC to set. Maybe that DTC is only at the Intermittent, not Confirmed status. If true, then it did get set during this event.
It's very unlikely the reman process metals left behind could remain hidden 15k miles. In fact, since it ran this long, I'd be surprised if it turns out to be a reman error. CGPT threw on the table that at 75k miles the cam chains could be stretched.
I know I'll hear some pushback for this, but this is the deal. Chains do not stretch. I raced dirt bikes with my two boys in 50-mile woods courses 20+ races/year and training on the off-weekends. I replaced all our good chains and sprockets after year 2, and 4. That's 40 harsh races each some nothing but mud, or creeks, all 4 seasons, with each of us hitting our bikes all out, but never adjusted a chain tensioner. I did replace aluminum rear sprockets/4 races. Chains appear to be stretched but it's the links which are destroyed. When a sprocket wears the teeth loose material. The chain links cannot pull on all the teeth they should together, and the force is too much for fewer teeth. The forces are also too much for fewer chain links. The drive system will collapse quickly as both the chain, and the sprocket are overloaded.
All this is also a factor for cam chains. These systems typically fail because the nylon tensioners get their tension from the motor oil system. The motor oil is supplied through these teensy-weensy tear ducts which we always find clogged. along with the VVT actuators. That's why the engine is in for a cam chain system overhaul, or much, much worse. The engine wouldn't be in a shop if they changed the correct oil on schedule. The tensioners and guides keep the chain links correctly engaged with enough teeth on the gears. The ECU and VVTs cannot control the cams with too much chain slack which comes and goes especially under very high engine loading.
Okay I'm said too much. I'll just list all the thing CGPT thought you should do, but it doesn't pass probably, or most even possibly could have occurred.
Cam phaser mechanical failure. These could be inoperable if oil is not available, mech failure on this day is not possible
P0087 – Fuel rail pressure too low
P00C6 – Fuel rail pressure too low during cranking
He wasn't cranking the starter while at 80% power on the highway. If C6 had failed a prior day, he would've noticed a MIL. This low-pressure alarm on the HP fuel system would explain the sudden engine power loss. However, the fuel failure I doubt it would cascade into the subsequent cam system control failure. What is the mechanism for that to happen?
I have seen a single sensor, one with a ground reference, +5VDC, plus an output wire. That stupid sensor failed internally by shorting the +5V to ground. That caused a bunch of sensors reports to be very wrong, so the ECU was losing its mind. I don't know if the Cam Controls or HPFPs are on a CAN.
To cap it off, CGPT then issued a list of 7 items for the tech to do in priority order. CGPT suggested this would be the quickest process for the tech to follow. First on the list is to run the engine until it's hot. I think I'd start with a scan and customer interview. CGPT thought we should fire it right up before we know it can supply oil, ironically to measure the oil level.
ChatGPT speaks with such confidence even while misleading all who listen. Please look a bit closer to see how these platforms operate. The list of advice is really what most people think makes sense to them, so they polluted the internet with their ideas which sound good but lack basis. The LLMs search, collect, and present in a new and clever way. Yet, all this is still equivalent to asking everyone at your kid's ballgame to diagnose a lump in your neck.
I gave it a try,I got a long narrative that failed fundamental logic. Let's check the advice it sent here. It suggested 3 of 4 VVTs all mechanically failed at the same moment in time. These VVTs then followed up by "triggering" the low fuel pressure codes on the fuel rails. There's no way all those units mechanically failed in unison, also conspiring to throw the same codes. CGPT could have easily not mentioned all this, because it can't happen, but keep in mind its not intelligent, either artificial or real. It can only regurgitate info from internet searches. No, these VVTs stopped working due to a failure higher in the architecture which handles all 4. The VVTs did not all get stuck, nor the solenoids or valves all just quit together, kinda like going on strike. Whenever multiple subsystems quite together, I go upstream looking for a module in common the subsystems depend upon. The same issue strikes off this list cam chains, tensioners, guides and all. Cam drive troubles hit cams in both banks with separate drive systems, at the same moment.
Now for the High-Pressure fuel system. The CGPT just list every single thing from the internet which mentioned fuel. This code P00C6, cannot be set unless the starter is engaged. CGPT cannot use logic to show this error. Perhaps the code is historic, or maybe you tried to start it before you pulled the codes. If historic, it would not be included in this failure scenario. This HP fuel system is remarkable in many ways. The fuel tank has two pumps to handle the saddle tank issue, and a common controller between them. If any of the 3 would have had a problem, there would be a code reporting that system, not the high-pressure system. There are two HP mechanical fuel pumps which are engine driven. The fuel rail pressure is variable. Max pressure is150 ATM, and it is used often. Techs would not try to measure that pressure when it's so easy to get from the ECM which also proves the pressure sensors. Our engine controllers have specific limp mode features which limit maximum RPM, it does not have a way to limit fuel delivery. There are a few different RPM limits depending on the level of risk to the engine. There are many failures which cause rough running, most do not also trigger a limp mode. I'm surprised the controller didn't shut this car down.
CGPT uses the shotgun diagnosis method. So, about 10% of the comments are worth the effort.
Your CATs might fine. If that code is new, it's possible it was triggered by this event, but very unlikely. That code doesn't turn the MIL on until the system measures the exhaust over the limits 2 consecutive operations. So, a single exposure cannot alone cause that DTC to set. Maybe that DTC is only at the Intermittent, not Confirmed status. If true, then it did get set during this event.
It's very unlikely the reman process metals left behind could remain hidden 15k miles. In fact, since it ran this long, I'd be surprised if it turns out to be a reman error. CGPT threw on the table that at 75k miles the cam chains could be stretched.
I know I'll hear some pushback for this, but this is the deal. Chains do not stretch. I raced dirt bikes with my two boys in 50-mile woods courses 20+ races/year and training on the off-weekends. I replaced all our good chains and sprockets after year 2, and 4. That's 40 harsh races each some nothing but mud, or creeks, all 4 seasons, with each of us hitting our bikes all out, but never adjusted a chain tensioner. I did replace aluminum rear sprockets/4 races. Chains appear to be stretched but it's the links which are destroyed. When a sprocket wears the teeth loose material. The chain links cannot pull on all the teeth they should together, and the force is too much for fewer teeth. The forces are also too much for fewer chain links. The drive system will collapse quickly as both the chain, and the sprocket are overloaded.
All this is also a factor for cam chains. These systems typically fail because the nylon tensioners get their tension from the motor oil system. The motor oil is supplied through these teensy-weensy tear ducts which we always find clogged. along with the VVT actuators. That's why the engine is in for a cam chain system overhaul, or much, much worse. The engine wouldn't be in a shop if they changed the correct oil on schedule. The tensioners and guides keep the chain links correctly engaged with enough teeth on the gears. The ECU and VVTs cannot control the cams with too much chain slack which comes and goes especially under very high engine loading.
Okay I'm said too much. I'll just list all the thing CGPT thought you should do, but it doesn't pass probably, or most even possibly could have occurred.
Cam phaser mechanical failure. These could be inoperable if oil is not available, mech failure on this day is not possible
P0087 – Fuel rail pressure too low
P00C6 – Fuel rail pressure too low during cranking
He wasn't cranking the starter while at 80% power on the highway. If C6 had failed a prior day, he would've noticed a MIL. This low-pressure alarm on the HP fuel system would explain the sudden engine power loss. However, the fuel failure I doubt it would cascade into the subsequent cam system control failure. What is the mechanism for that to happen?
I have seen a single sensor, one with a ground reference, +5VDC, plus an output wire. That stupid sensor failed internally by shorting the +5V to ground. That caused a bunch of sensors reports to be very wrong, so the ECU was losing its mind. I don't know if the Cam Controls or HPFPs are on a CAN.
To cap it off, CGPT then issued a list of 7 items for the tech to do in priority order. CGPT suggested this would be the quickest process for the tech to follow. First on the list is to run the engine until it's hot. I think I'd start with a scan and customer interview. CGPT thought we should fire it right up before we know it can supply oil, ironically to measure the oil level.
Very good insight! Now that you've posted your knowledge, the next version of the LLM will be trained on your post, and the model gets even better!
These generative AI tools are not perfect, but they get you about 50% of the way there. Last year they only got you about 30% of the way there. Each year, they get closer and closer to solving most of the very basic problems, leaving the most complex ones for the human mind to solve. (We won't be replaced by bots anytime soon
Additional information from the first indy mechanic after having it towed to the shop:
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Oil drained from the engine. All clean, no metal found in oil or oil filter. There is no oil pressure.
They believe either the oil pump failed and caused engine damage or the timing chain failed.
--
I took my original post from this thread along with the additional info from the mechanic and prompted Gemini (Google's ChatGPT).
Here's what it said:The key piece of information is: "there is no oil pressure"
With the combination of the original codes (P000A/C, P0011/21 for timing) and the confirmed lack of oil pressure, the most likely root cause is a Timing Tensioner Failure which led to a Timing Chain Failure/Jump, and consequently, loss of oil pressure.
Here is the breakdown of why this sequence is the most probable:
🎯 Most Likely Root Cause: Timing System Failure Leading to Oil Loss
On the Jaguar 5.0L Supercharged V8 engine, the timing system and the oiling system are deeply intertwined in their failure modes.
1. The V8 Timing Tensioner/Guide Problem
• A failure of the Timing Chain Tensioner or Guide is a well-known weakness on earlier iterations of this engine design. When a tensioner fails, the timing chain instantly develops slack.
• Result: The chain jumps teeth on the sprockets. This instantly throws the camshafts out of time, which perfectly explains your original codes: P000A/C, P0011/21 (Camshaft Timing Faults) and the sudden stop in acceleration.
2. The Loss of Oil Pressure
• The oil pump on this engine is mechanically driven, often by the crankshaft or the timing system components.
• More significantly, when a catastrophic timing failure occurs, the sudden shock and metal-on-metal contact inside the timing cover can cause immediate and severe damage to the oil pump drive mechanism or lead to a massive internal failure that prevents the pump from building pressure.
• Result: The engine quickly loses oil pressure, which explains "there is no oil pressure"
⛽ Fuel System Codes (The Secondary/Consequence Codes)
The fuel pressure codes are likely a consequence of the severe timing issue, not the root cause.
• Why the Timing Issue Causes This: The HPFP is typically driven mechanically by one of the camshafts (or the timing chain/belt). If the camshaft is drastically out of time or not moving correctly due to a mechanical failure, the pump will not be driven properly, leading to a sudden, catastrophic drop in rail pressure and setting the fuel codes.
⚠️ Catalyst Code (The Tertiary Code)
The P0420 code is also a consequence code.
• Why the Timing Issue Causes This: When the engine timing is severely wrong (over-advanced/jumped chain), the combustion process is completely thrown off. This results in an incorrect fuel/air mixture being sent into the catalytic converter, which makes the Cat fail its efficiency check almost instantly.
Here's what Gemini says now with the additional info from the reman shop:
That is a very specific and technically sound diagnosis. On the Jaguar 5.0L V8, the vacuum pump is driven by the same auxiliary chain that drives the oil pump.
If the vacuum pump seizes (locks up), the sudden mechanical resistance snaps that drive chain. Because that chain also turns your oil pump, you lose oil pressure instantly—which leads to the "slow response" timing codes (the VVT system needs oil pressure to move the cams) and eventually internal engine damage.
I just pulled an invoice from my local indy shop because I remembered they replaced the vacuum pump with a new one at the end of June 2025 (less than 6 months ago).
The plot thickens. I'll let you know the outcome, probably many months from now.
Meanwhile, I just approved the install of the new reman engine.
We actually make a vacuum pump delete kit. While not for this intended purpose, this kit would remove the mechanical vacuum pump in favor of an electric version. Almost all AJ126 & AJ133 engines utilize a mechanical vacuum pump to drive the brake booster. This pump is located very close to the crank pulley, and belt failure at high speed can easily take out the vacuum lines. In your particular situation this kit would avoid this failure from occurring in the future on the reman engine you are getting.
I just pulled an invoice from my local indy shop because I remembered they replaced the vacuum pump with a new one at the end of June 2025 (less than 6 months ago).
The plot thickens. I'll let you know the outcome, probably many months from now.
Meanwhile, I just approved the install of the new reman engine.
Did you have to pay for the replacement reman engine or was it done under warranty?
I had taken it in to the shop for some noise from the rear tires while driving. There’s another thread started by me on that one back in June. While it was in the shop, they found oil leaks, one near the vacuum pump gasket (see attachment), so I had that repaired.
They said while they’re in there, they might as well replace the vacuum pump. They ordered an aftermarket one from their normal parts supplier, Worldpac.
Going forward, I’ll lean toward replacing with an OEM part, even if it’s more expensive, unless the design of the OEM part is already identified as a weak point (e.g. plastic coolant pipes).
After the sudden loss of acceleration on the highway, I was able to brake easily, so I don’t think the power brakes were compromised, but I didn’t have to brake hard. I safely coasted to the next exit and parked as soon as I could in a safe spot.
P000A P000C P0011 P0021 P00C6 P0087 P0420 Sudden loss of acceleration
