I finally figured out how to record live data on the scanner so I hooked it up and started the car. It took 3 tries before the engine would start. I then drove around the block for 15 minutes. From glancing down at the scanner from time to time, I could see that the STFTs were pretty high at around 25-30%. As I said, after 15 minutes, the car started acting up like usual. I pull over and the car starts misfiring with the CEL blinking, so without thinking, I panic and turn the engine off...without saving my live data first!!! ARGHHHHH

I calm down and read the codes...cylinder 6 and 8 misfire, P1315: Persistent Misfire, P0300: Random/Multiple Cylinder Misfire Detected. The last time I got misfire codes was before I replaced the MAF sensors...cylinders 1, 2, and 4 that time. I set the scanner to record live data again and restart the car. It takes a very tries but it grumbles itself to life for a few moments while I can get some readings. It was shaking hard and there was sound I'd never heard before coming from God knows where, like a squeaking wheel. I save the data and put the engine out of its misery for the night.

This is my first time ever trying to interpret the multitude of live data log info so I'm not 100% sure of what I'm looking at yet but from what I can tell, I don't think its a fuel delivery issue. Pressure after sitting for a few minutes and just before starting the engine was 899psi, 2205-2228psi while cranking, 1834psi at 1009rpm, 1726psi at 648rpm (which seems high for that speed but I believe the system is attempting to compensate for the lean condition). I think those numbers are pretty much normal but I need to confirm that.

Now, the fuel trims...in Open Loop, they read:
STFT 1: 0%
LTFT 1: 26.6%
STFT 2: 0%
LTFT 2: 30.5%

Closed Loop, at 648rpm:
STFT 1: 25%
LTFT 1: 43%
STFT 2: 25%
LTFT 2: 38%

At face value, those numbers seem to indicate a substantial vacuum leak but I'm wondering if there's any other data in the log that will help corroborate that.

I guess my next course of action is to try and get another full live data recording showing me what's going on the moment it goes from driving fine to jalopy with the wheels falling off. And I suppose a smoke test is also in order. Thank God I don't have to commute to the office anymore.

 

Yes those fuel trims look awful. As your car is successfully going into closed loop, I believe that indicates all relevant sensors are perceived to be functioning. So at this point I too would also suspect a big vacuum leak somewhere. You definitely should get a lean code, but I guess that doesn’t really matter with trims that far off. IIRC it should trigger at either 25 or 30 ltft.

 

It is a 2015 XJL AWD with the 3.0 V6 gas motor. I just got through putting the VAP ECU tune on it.

 

I was wondering about that myself. No lean codes at all.

 

Somewhere I recall that a member may have had similar issue and found that there was a crack or two in the intake bellows that caused his issue of rough running.

 

Thanks for the suggestion but I'm using the Mina Gallery intake tube and everything seems nice and tight.

 

I had something similar on the old XK8. It would buck and jolt until I put it into "Sport" mode, then it would clear. I replaced the MAF with an after market one and, although the problem cleared, the car was dramatically down on power.

I gave the original MAF a serious clean and swapped out the up-stream O2 sensors,,,Viola! Back to normal. I know your codes don;t support the O2 sensors being changed, but neither did mine. If a sensor is supplying junk info, you get a junk output.

wombat

 

Thanks for the suggestion, but the upstream o2 sensors are brand new, just a few months old, Bosch brand. The midstreams and downstreams are also fairly new.

 

XJ8JR,

I hear what you're saying re the O2 sensors. I find it suspicious that the car gets to normal operating temp before it starts playing up....which is about the same time that the heaters on the O2 sensors shut down?

My only other suggestion is that the throttle body is dirty and the butterfly valve is sticking; Sorry I can't be of more help.

wombat

 

As I understand it, the engine runs off preset fuel tables until the o2 sensors are heated up, at which point the engine will run off their readings. The fuel trims are still pretty lean even before the o2s heat up, around 25-30% both banks, so my first guess is a big vacuum leak somewhere. From researching online, my next suspects after that are the MAP sensor, throttle position sensor, and crankshaft position sensor, but I'm going to perform more diagnostics before I just start replacing things. The throttle body was nice and clean last time I checked.

 

I replaced my front grill, lower grille, and side grills with blacked out pieces from Mina. I was extremely excited for my test drive to the hardware store and back, to test if fitment would last a medium speed drive on a windy day. On the way there, all great. On the way back, weird noise from the left wheel well. About a mile out from home I noticed something at idle, which sent some alarms through my head and I got into the left turn lane to the nearest gas station. Car hit restricted mode, engine light on. I shut down immediately and called the cops as I was almost in a major intersection. Car would not start though I tried a couple times. Due to the install, my battery was low so I was using this time to recharge as well as pick up some building supplies. I am not sure if my music was too loud/battery draw too much for the recharge process as I know this can cause issues also.

As I waited for my tow truck, I checked my oil and BOOM showing underfilled. The last time I checked was in August and it was full to the top of the 'meter'. I used BG44k last week but otherwise have not made any changes.
I had an oil change appointment for Nov 16th planned a few weeks in advance, so I called the dealer and they said they could modify the appointment. They were too booked up this week and next to look at it.
Once it was towed home, I filled it with 2 quarts, as that's all I had of the Castrol 0W20 on the shelf. I am quite concerned the tapping sound I heard was the VVT and I was running on low/no oil.

I checked my codes after I shut the car off, and it was showing P0027 and P0011. I think there were a couple more but in my dumb excitement I accidentally cleared the fault status with my code reader SMH.
On a positive note, car looks great with the new blackout pieces. I'd been waiting to install them for months, finally got around to it today.

 

I'm sorry to hear all that. What was the weird noise you heard and what was it you noticed at ide? Have you tried starting the car after adding the oil?

 

Thanks. Sorry to hear of your troubles as well. Ticking/flapping noise, which in my heart knew was bad news. I switched from sport to drive, and it went away. That's when I got in the lane to turn into the gas station.
I had originally heard it briefly and thought it might have been a loose grille component, as I had trouble getting one of the lower grilles to seat properly at first. Once the drive symbol started blinking and my engine light came on, I knew it hit restricted and shut off engine right away. I was about 20 feet from a huge intersection. Some guy drove by to tell me I should have bought Japanese. LOL.

Once I got home, I inspected what I could via the oil fill port but pretty much a black box at this time. It won't start now, I have it charging with my CTEK now.

 

Changed the diff oil, transmission fluid change, replaced the RH leaking headlamp washer, engine oil & filter change, fixed a few of the sticky buttons, replaced the cup holder, reset the service message and checked fault codes @ 109000kms. '11 XJ Portfolio.

 

In the spirit of the thread, I got a second opinion from a performance shop that I have worked with in the past and they agreed it's seized. Best guess is lack of oil, based on when the sensor read full, I interpolate I was actually 5 WHOLE QUARTS short!! This is over a 7 month oil change interval, I admit I usually change on the dime at 6 months or 5k miles. However, this spring my Dad passed away and had added a lot of research and craziness to get my family on the short path to a positive future. I am lucky that it is only an engine and no one was hurt. No oil pressure light or sounds prior to the pinging that I heard while I was on the road. No low end knock at all. I still believe I jumped timing first. Definitely consumption, I have been sending in my oil reports for the last year and a half and no issues. Also I found no leaks and the shop verified.


I authorized a swap for a used motor with 50k miles, and the shop can update the timing chain tensioners/levers for only $900 parts and labor. About 13k all in. I will get the car back before Christmas.
I did not bother with the dealer, they've always been useless around here.

 

Yikes, I'm sorry to hear that.

 

Well, I think I may have found the source of my supposed vacuum leak. One of the throttle body bolts had sheared off and was just sitting in there all loose. So, not only was the throttle body gasket not snugged up but also the bolts have little rubber gaskets of their own under the bolt head. I've got the throttle off and I'm going to be ordering new bolts and a new gasket but now the question is how do I extract the threads...

Edit: There was just enough of a burr left on the bolt to get a small chisel and hammer on it. A few taps and it started twisting itself out. Praise God.

 

Congratulations and yes very lucky!!
Great troubleshooting to I would have never found that.
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Did you smoke test it to find that leak or did you just start dissembling it and found it?

 

I did a shadetree smoke test with a cigar and didn't see anything but it admittedly wasn't the most scientific or professional procedure. I'd like to try it again more thoroughly to make sure there are no other leaks I'm missing. With the crazy high positive fuel trims I was seeing, I was sure I was going to find something more substantial than one corner of the throttle body gasket but maybe that's enough to do it. I caught the broken bolt only on a hunch while poking around.

For the life of me, I cannot find the part number for the bolt anywhere online. I may have no choice but to visit/call the dealership...