Will P
2000 XJ8 vanden plas
82,000 miles
Alpine Green Queen

My 2000 XJ8 VP suddenly went into what I thought at the time was a crazy strong restricted mode, the engine was running barely but extremely rough, I lucky was able to kind of dodge the traffic and get off the road. After parking a few minutes it cranked then, I took a less crowded route back home, about a mile or two, in as I what I now think was “limp mode” which is way more disabled than the restricted mode, I didn't really know that mode even existed, I felt lucky to make it home and get it parked safely.

Approached the car with obd II reader and thought before I'll just crank it and refresh the cars behavior in my mind. It cranked, roughly and the transmission was locked couldn't move the gear shift. I read the codes and wrote them down. I had planned to do this and then clear the codes, crank it and see how it ran and then after a good running check the codes again, planning to swap bad reading coil with a good one. Trying to verify my initial findings.

The codes 6 and the 7 pending the first code reading
P303 cyl A-3 misfire
P1316 severe misfire
P128 coolant temp below
P352 coil a-2 mal
P353 coil a-3 mal
P355 coil b-1 mal

Pending
P128p
P137p
P352p
P353p
P355p
P1000p all reading not complete
P1368p ignition bank B mal incl. Coil B1,A2,A3,& B4 if I'm reading it right in the code explanations.

Okay, cleared those codes and the restricted mode goes away and the transmission shift into gear as normal, rocking back and forth in forward and reverse. I ran it long enough and high enough that it went into the restricted mode but “not” the red, and I assume the limp mode. I have a very recent new battery and it cranks better than ever.

Codes, shocking to me read on the second reading.

P301 cyl a-1 misfire
P306 cyl b-2 misfire
P307 cyl b-3 misfire
P1316 severe misfire, excessive emissions

Pending codes read
P300p random misfire
P301p
P306p
P307p
P308p cyl B4 misfire(different bank than the above three If I am correct)
P1316p
P1000p

So you see the changes. Right now does it seem like a coil issue? I thought the coils on one bank were the problem and then after checking them again, it was the other and one in the previous bank not listed the first time. I'm not driving the car, of course, I have another. I'm retired and not auto tech savvy. When I can. I'm going to take a run at solving this and I hope I can get some suggestion about what to do next. Our closest Jag dealer is about 100 miles away and I probably couldn't afford a super expensive job anyway with a potential timing tensioner replacement looming. I may be delayed in implementing any suggestions for awhile while I deal with health issues but I will return and post on this until it is done. Thanks for any help. Anyone know a good and reasonable mechanic in Montgomery, AL, Thanks, Will P

Afterthought, what about erasing these codes and going through two more starts and high revs, then read them again to see if they are consistent? Or maybe doing my restarts and revs without clearing codes to see if I get additional codes.

Any questions,let me know. I will accumulate all the information I get from responses, and used it when I can.

 

I always start by checking my battery's health.

 

It's good, just got it replaced at first of the year, cranks easily. My last battery was unbelievably 12 years old. Thanks, Will

 

The common denominator besides the battery health would be the Crankshaft position sensor different then the Camshaft sensor .

Important to check the timing chain tensioners before damaging the valves .

 

I'll put that on my list! Thanks, Will

 

Looks to me like a every day timing issue from broken secondary tensioners: You need to replace those secondary tensioners.

 

Thanks Jim! That makes sense if it blends with my experience just a few minutes ago. I would like to know if you still think so after this, if so should I not crank or drive it at all. I'd like your input.

here is the latest troubleshooting effort, which was confusing to me but maybe someone gets it.

Okay, went back out and cranked the Jag and ran it awhile, an suddenly the yellow restricted light went out and the engine smoothed out and actually sounded like I had 8 cyl. Seemed to run perfectly. I still too cautious to drive it but I cut it off and back on and ran great, like all my prior efforts had been a bad dream. Ok, I checked the codes and had
P300
P301
P306
P307
P308
P316 (May have been? 1316, “senior moment”)
P1000p and no other pending

But it's running fine so I thought I'd clear the codes and see what had changed.
Cleared them
Ran and while cut off and had only
P1000p

Ran a good while again and this time the yellow came back on and the engine ran very rough
checked with new scan and got
P306p
P307p
P308p
P1000p

Started again and no restricted again for a while then the very rough came after a while and dreaded yellow.

Stopped and re-scanned
P300
P301
P303
P306
P307
P308
P316 (May have been? 1316, “senior moment”)
P1000p

I know I'm probably asking a dumb question but if the thing runs well when you clear the codes but then with all the cyl. misfiring this after it goes in to restricted should point to some part of the controls wouldn't it. Rather than the coils all going at once as of now I just have misfires codes and no coil faults specifically? Where previously I had coil faults

Any help is appreciated. Thanks Will P And does this still point to the tensioner issue? If it is a broken tensioner why does it clear up and run smooth, I'm had no tell tell signs that I'm otherwise aware of.

 

For now, you are just slightly off in timing. Will get worse or you will bust a valve or two.

Over on the XK8 forum someone had this problem a couple of years ago (maybe five now). Most of us were sure it was a timing issue, wound up it was dirty and corroded ignition units (coils) on each plug for the offending cylinders.

Might also be leaking part and full load breathers; maybe dirt throttle bore and plate; issues with the Throttle body itself; maybe bad or dirty MAF.

Still: sounds like timing. But maybe one of the pros will weigh in.

 

Thanks so much, Jim. I'm going to take all of that into consideration and any additional info if others contribute. This is such a nice car but I only drive it about a thousand miles a year, paying insurance and all the possible new expenses, knowing at some point soon I'll have to get the tensioners done. I've got to consider. But, for now, I'll wait and see. If I eventually sell it, someone younger, healthier and more knowledgeable could make her purr and have the car for a bargain price. I can do coils and plugs but not so much beyond that.

 

2000 XJ8 vanden plas
83,000 Alpine green

Just wanted to update the post. After doing a lot of reading on the site from so many different members I've kind of settled on the likely cause of a big shift in my OBD2 readings which I thought might be extremely valuable in diagnosing my recent car finding. Probably, though my current battery is very new, the readings from my OBD are about two years old, and that includes about twenty dead batteries and twenty chargings and I never realized that batteries (my old one was 12 years old)that are that weak can cause the very sensitive sensors to give odd readings. So the old codes could relate to that and from two years ago. Heck, I had no problems so why read the codes. Indicating to me that they might not be significant to my current problem at all as far as a diagnosing tool or marker.

Still got my problems but I'll address it from another avenue in another post which may add to the helpful information collected from King Charles, Lady Penelope, and Jhartz.


Will P

 

Erase the codes and get a fresh start.

 

I will, thanks... Will