I have two items that I am requesting assistance on. First is a perplexing misfire problem and second is for those who may be familiar with the AutoEnginuity scan tool and DLC issues. Please excuse the long post, but I wanted to explain all that has happened since the problems started.


Vehicle: 2001 Vanden Plas (non-supercharged). No history of powertrain problems.

2 Months ago had oil changed. The shop put in Pennzoil Ultra Synthetic 5W-20 instead of the Mobile-1 5W-30 I normally use. I noticed a significant degradation of performance, so I changed the oil back to M1 again after 500 miles, which seemed to fix my problems. At the same time, I changed the air and fuel filters along with the spark plugs as the car was crossing 110k miles.

I then took the car on a 500 mile trip. After 1 ½ hrs of driving, the MIL came on along with the restricted performance indication. Having the codes read at a part store when I got to my destination, the codes were P0300/0304/0305/1000/1313 and 1316. This is much the same as numerous posts I have found on these forums. So I figured it had to be something with the new plugs since I had used the cheaper NGK platinum “equivalent” in lieu of the $15/ea OEM plugs. The next morning the MIL and restricted performance was gone and the car ran fine.

The same thing happened after 1 ½ hours driving on the way home. I used a code reader from another parts store and it showed P0300/0304/0354/1000 and 1316. When I pulled the plugs, almost all of the platinum coating was gone off all of the plugs. I measured the gap (since these were supposed to be pre-gapped platinums) which was 0.050. The manual states that the gap on this car should be 0.040 – 0.043. I took the plugs back and told them that they did not match OEM specs for my car and I replaced them with the NGK iridium plugs (since they are supposedly better than OEM). I also swapped the #4 and #3 coil packs because of the 0304, 0354 and 1316 codes. The car ran fine after this until I had another long drive. Again, after 1 ½ hours of driving, the same restricted performance problem happened. Codes pulled from a third part store’s scanner were P0300/0304/0354/1111 and 1316.

Summarizing the misfire problem, it only happens after driving for 1 ½ hrs so I believe it has to be temperature related. It is giving the 0300 code indicating random misfires on multiple cylinders. But, except for the first instance, the only cylinder that trips a code is cyl 4. I don’t have any codes that indicate MAF, EGR, EVAP system, throttle position, timing, etc…. I have changed the plugs and fuel filter, swapped the coil pack on the affected cylinder and thoroughly inspected the wiring harness. The only thought I have left is maybe a leaky injector on cyl 4? I don’t know what else it might be.

Last item, I noticed yesterday that while the restricted performance is occurring, if I push the sport mode button, it will normally clear the issue until I increase the load on the engine (hard acceleration, going up a hill, etc…). I think maybe if I can isolate exactly what the sport button does to change engine performance, it may help determine the cause. I have read several times in this forum, individuals stating that the only thing the sport button does is change the shift points. However, my owner’s manual gives two different ride heights, one for normal mode and one for sport mode and I can notice a definite improvement in throttle response in sport mode, so I am sure that it does more than simply change the shift points.

AutoEnginuity:

With the above issues, I decided to buy the AutoEnginuity scan tool to assist in troubleshooting. This was as good an excuse as any and I have wanted to get the tool for some time. I received the tool and it would not communicate with my Jag. I tried it on my other vehicles (99 Ford Contour and 05 Ram 1500) and it works perfectly. Talked and emailed with AutoEnginuity and they concluded it must be a problem with the vehicle since the tool works fine on my Contour which uses the same protocol as my Jag. Upon inspecting the DLC on the car, there was noticeable corrosion on pins 1, 2, 9 and 10. Not real bad, but enough to possibly be a problem. I cleaned the contacts with a micro file, small wire brush and compressed air. When I plugged the tool in again, it popped my trunk and cycled the door locks and still could not communicate. I took the car back to a fourth parts store to ensure they could still pull the codes and they also had no issue retrieving the codes with their handheld scanner . I can’t figure out why four separate parts stores are able to read codes on my car, all using different handheld scanners, but my AutoEnginuity tool can’t communicate. Since the only way to get a replacement DLC from the dealer is to buy the entire dash harness ($3,000… really?!?), I went to a salvage yard and cut the DLC out of a 99 XJ8 and plan to swap it out, however, I would like to test my DLC with my multimeter first. Does anybody know how to do this? What are the expected voltages on which pins? Which pins are paired? I don’t want to bridge positive this with positive that and accidentally short something. Both the DLC on my car and the salvaged one have wires for all 16 pins except for pins 3 and 11. Also, does anybody have any idea what would cause the corrosion present on my DLC when there has been no damage to the vehicle?


Thanks in advance for any assistance you all are able to provide.

 

Dave, I know you're a couple hours away, but if you want to come down to Ft Worth, we can look at your AE tool, you can try my unit (which works perfectly) and see if we can find out why its not connecting, and try to diagnose your misfiring. It does take some time to connect to the car, sometimes 2-3 minutes. I suspect, the bad coil is still there, and you only notice it after long term use (and higher temps). If you want to be sure about this diagnosis, change them all to new ones. They say that when one coil goes, the others will soon follow if not replaced promptly.

I'm afraid I don't know much of anything when it comes to voltage on the DLC.

 

Thank you for the quick response and offer. I'm always looking for an excuse to get down to the DFW area. If you could PM me the info on where you are at and a contact phone number, I'll plan to take off work on Friday and try to meet up with you if you are available. I absolutely do not want to cut the DLC on my car without being 100% sure that it is definitely the problem. It would be nice to meet up with another member if nothing else. After that long of a trip, I'm sure that the car will be acting up when I get there, so it may help to troubleshoot it that way instead of taking it someplace local. Since I seem to remember that you have the AE Jag enhanced interface, I am wondering if the non-ODB II connections work. I have only purchased the basic AE tool for now.

My thought on the coil pack was that if it was the coil pack, the codes should have changed from 0304 and 0354 to 0303 and 0353 when I swapped the coil pack from cyl 4 to cyl 3. But then again, I absolutely would not call myself a mechanic, just a hobbyist when it comes to working on cars.

I will try my AE tool again and let it run for 3 - 5 minutes trying to connect, just to make sure. I have not let it run for more than about 1 to 1 1/2 mins trying to connect so far. It connects to my other vehicles in less than a minute every time, so I guess I have been expecting the same on the Jag. I'll post the results of waiting longer in just a few.

Thanks again.

 

Ok. Just to make sure of the connectivity issue, I tried connecting the AE tool and waiting 5 minutes each time. I tried both auto-detect and J1850 PWM on ignition on/engine off and ignition on/engine running, 5 minutes for each attempt. Still no success connecting. (It did pop the trunk again when I plugged the AE connector in, so at least it's consistent )

 

BC - are you sure you swapped the correct coils? Remember the cylinder designations --> A1-4, B1-4 and their crossover to 1-8 is somewhat strange.

Attached is the numbering diagram:

 

Quad,

Thanks for the diagram. I admit that I was somewhat perplexed trying to locate cylinder 5 when I got the 0304 and 0305 codes the first time the misfire problem happened. Thankfully, I found this same diagram elsewhere along with an explanation of cylinder numbering on this forum (maybe posted earlier by you?). Using the diagram, I swapped the coil from Bank 1, Cyl 4 with the coil on Bank 1, Cyl 3. Please correct me if that is wrong. Thanks again.

 

The real issue is whether the code reader is correct, I think... because even the Jag diag code description seems to confuse the issue even further. Attached below, it states that A4 is cylinder 4... yet the diagram implies that A4 should be 7. AND, the numbering diagram uses 1-1, 1-2, etc. nomeclature, yet the code descriptions use A1, A2, etc.

Heck, even I'm getting confused now!

 

that's why I suggested replacing the entire bank... I like overkill.

 

I'm pretty sure that they are numbered as follows:

Passenger's side front to rear: 1, 2, 3, 4
Driver's side front to rear: 5, 6, 7, 8

Maybe one of the techs could verify the cylinder locations referenced by the 0301 - 0308 codes. Or, maybe I should swap all of them just to make sure? Don't know about replacing the full set. At over $1,100 to replace all of them ($148/ea) it's a little cost prohibitive as just a troubleshooting step.

 

As I read the DTC table and the cylinder ID, that makes sense. I would suspect more than one on Bank 1 is failing.

I checked online with one of our sponsor dealers, and the coils are only $105 shipped, so even if you decided to do just bank one, you're not looking at that much of an expense.

 

That's a much better deal than what I have been able to find.

Any idea on the spark gap issue? All of the "OEM" plugs I've looked at at the parts store are pre-gapped to 0.050. The owner's manual states the gap should be 0.040 - 0.043. Since you can't gap platinum and iridium plugs, how do you address this issue? Have the specs changed since the manual was written?

Also, pertaining to the 0300 code, does this code trip whenever a 0301 - 0308 code trips or is it possibly indicating that I have stored pending codes that the basic handheld scan tools can't access. I am just wondering why, if I am only getting the 0304 and 0354 codes, is the 0300 code indicating multiple cylinders there also.

 

I checked the first two iridium plugs I removed from the packages last week, and they were within a few 0.01 hundredths, so I didn't have to check any more, nor gap any of them.

Can't tell you about the code question, I only used it one time to diagnose a Lincoln LS cylinder misfire, my AE program said cylinder #8, no other codes...changed that coil, and all was good. I'm still leaning towards more than one coil of yours is dying.

 

Woooah, where did that come from? I just checked the Vehicle Specification manual (for ALL Jag models, document dated 2004) that I referred you to in the FAQ section of the XK8/R area...and it shows this...

 

h20boy,

Sorry, I've been a little busy and off the forum for a while. You were correct, the problem was a coil pack. I swapped all of the coil packs with each other. I swapped 1-8, 2-7, 3-6 and 4-5. This way, every coil pack was now in a different cylinder position on a different bank. After I did this, the misfire code changed from 0304 to 0305. I replaced the #5 coil and the car is running as good as new again.

I still have the frustrating DLC issue where I cannot connect to my AE tool, but I can connect with the handheld units at various auto parts stores. I may still try to make a trip to FT Worth and see if your scanner can connect. If so, I'll get back with AE and see if they will swap my connector. I'll be taking a 3500 mi cross country drive next week (1st vacation in 6 years) in my car while my truck is in the body shop. I'll try to set something up after we get back to come to Ft Worth and meet up.

On a side note, I found a wonderful deal on tires and I wondering if you had heard anything about them. Yokohama Advan S.4. 5yr or 1/16" remaining tread wear warranty, W rated, all season sports tires for $123 ea (regular price). This is much cheaper for what appears to be a much better tire than I have used before. They were difficult to find and I had to order them and wait 1 week for them to come in. But, I think it will be worth the wait.

 

Dave,
With your scanner, you might try another car of your year and model, if you can find one nearby. As you have said, changing the plug should be your last resort. If it fails on another vehicle like yours, that would confirm it. Since every other scanner you have tried, seems to work, I suspect the connector on your car is just fine. I have the similar but inexpensive OBDII type, which for engine codes works great on every car I have plugged it into. (XJR, Ford Escape, Audi A6, Chev Blazer, Acura). It connects in a few seconds. Aside from taking the trip to Fort Worth, perhaps see if you can find another VDP to scan.

Just a thought.

 

Also dave, if you want, give me a call, I'll walk you thru how my AE is setup to connect, see if we can get it to work.

Why don't I ship my unit up to you with the software, and see if it'll work. I'd hate for you to make a trip all the way down here just to see if the connector works on my AE hardware.

Either way, just give me a buzz.

 

JWT,

Sounds like a good idea, however, I would need to locate somebody with an 01 XJ8 in the OKC area that would be willing to let me hook it up to their car. That seems like a fairly difficult proposition. I may post something in the XJ8 forum just in case we have a member in OKC with the car I need who wouldn't mind helping. I did notice that my AE connector has all 16 pins while the other handhelds I've used are missing several. This, in conjunction with my trunk popping open every time I try to plug my AE connector in make me think that maybe the pins that are an issue are ones that the handheld scanners don't use. Just a theory though. My AE tool does connect successfully to my 99 Ford Contour and my 05 Ram 1500 and works beautifully, as advertised.


H20,

I think I will probably take you up on your offer, but as I said, I will be on vacation until Aug 8th. I'll PM you with my address after I get back. I very much appreciate the offer.