Errr - are these special plugs? Every plug I've ever seen has a flat topped centre electrode. These look like they're burnt away to a point.

 

Bank 1 plugs. They were a lot "wetter". As you can see, these electrodes are worn unevenly and there is carbon build unlike bank 2.


By the way the far right plug, closest to the firewall, has buildup inside the insulator chamber unlike the other 7.

 

I HAVENT BEEN FOLLOWING THIS THREAD MUCH SINCE ITS A RUNNER. BUT THOSE PLUGS ARE TOAST IN THE MIDDLE AND THE OTHER SET OF 4 ARE TOAST ON THE END. THE IR(IRRIDIUM) PLUGS ARE SLATED FOR 100K SERVICE, BUT I HAD BEEN DOING RESEARCH INTO DRIVABILTY ISSUES READING THROUGH ADVANCE TECH INFO ON ASE'S WEBSITE ABOUT PLUGS. EVEN THOUGH IR'S ARE SLATED FOR 100K SEVICE, "ALL" MANUFACTURERS SAID THE PLUG PERFORMANCE BEGINS TO GO AWAY AFTER 60K. THOSE ARE ADDITIVE DEPOSITS BY THE LOOK OF THE HARD LIGHT COLORED BUILDUP. ANOTHER ISSUE THAT THE PLASTIC BATHTUB INTAKES SUFFER FROM IS COLD START OIL VAPOR/OIL BUILDUP INSIDE THE INTAKE. AND THIS IS A PROBLEM WHEN COLD. INJECTOR CLEANERS AND INDUCTIONS CLEANER HAVE TO BE RUN A HOT ENGINE NOT COLD. THIS IS WHY YOU HAVE DIFFERANT GAS BLENDS FOR SUMMER/WINTER. TO EASE STARTING. IVE SEEN MANY CARS START ROUGH, ALITTLE BLUEISH SMOKE AND A COUPLE RAPS OF THE THROTTLE CLEARS RIGHT UP.
DONT KNOW IF YOUVE DONE IT OR NOT. BUT I WOULD PULL THE INTAKE, CLEAN OUT THE OIL POOL IN THE BOTTOM TOTALLY AND DECARB THE INSIDE. REPLACE THE GASKETS AND SEE WHERE YOURE AT ON THAT....
FUNNY TOO HOW JAGUAR AYS THE "CORONA RINGS" (BROWN DISCOLORATIONS AT THE BASE OF THE PORCELIN) HAS NO PROBLEM WITH THE PLUG PERFROMANCE( iDONT KNWO FOR SURE EITHER) BUT THE DEPOSITED PLUGS HAVE BIGGER DARKER CORONA RINGS, OR IS IT JUST ME? GO TO NGK, CHAMPION AND OTHER PLUG MANUFACTURER WEBSITES FOR ACCURATE PLUG READING INFO WITH PICS

 

Jahummer, I'm good with all Brutal said here, just be aware his plenum [intake] comments apply to NA engine, not you, you have a Super. The plugs have not eroded much, iridium plugs have a very small, point type center electrode, not the wide flat electrode of older plugs. I'm right on board saying those plugs need to be changed out, it's time.

I'll ponder more later, gotta run right now.

Cheers,

 

No doubt replacing them helps, but what I'd like to know is there anything with this bit of evidence that would indicate another concern with the motor or even something related to the idle RPM drop at stop?

 

jahummer,

I'm pleased that Brutal & xrguy have chipped in here. I don't know for certain, but i recall something from years back about the appearance of the corona having something to do with the temperature of the plug. And I think it was counter-intuitive. IE; the dirtier the corona, the lower the temperature the plug is at. If a plug is fouling in an otherwise sound engine, it meant that the plug needed to be upgraded to a 'hotter' range plug. But if the engine is worn & burning oil, that will only fix the problem temporarily. Does the car use oil?

The stumbling RPM at stop indicates an inlet manifold leak somewhere. When the throttle butterfly closes, the computer will be reading that to reduce the fuel supply to match the air flow. An inlet manifold leak post the MAF will dilute the mixture, and the RPM will drop too far. The outlet sensors (oxygen) will then tell the computer it needs to supply more fuel, and the revs will then pick up.

I think you have two problems going on, one contributing to the other.

Cheers,

Languid

 

jahummer,

I just flicked back and looked at the photo of the first four plugs to compare with the second photo. Looking at them, the dirtiest plugs look almost as though they have nt been as tightly seated as perhaps they should have been. It looks like you have had some combustion mixture leaking past the two centre plugs in the first photo, and the two right hand plugs in the second. Were they the plugs that were harder to remove?

Cheers,

Languid

 

Not that I know of.

What's a quick way to find an air leak? I did not see anything obvious.

 

The two with the larger coronas are also showing wet threads and the crush washers are looking a bit discolored too.
Languid is onto something.
Maybe leaking plugs.

 

Spray some ether or starting fluid in the intake valley area while the engine is at stable idle. If there's a leak somewhere, the engine will speed up as the starter fluid vapor enters the system. If no change, then probably no leak.

 

while acurate for big leaks. youll never find smaller ones like this. you have to minotr short term fuel trims while doing it to look for negative numbers when you hit a vacuum leak(negative meens pulling fuel from the injectors since youve introduced added fuel through the leak source) there are areas that you cant even get to on a sc engine too. i would pull off the wiper cowl to be able to access the throttle body area and back of the engine where most SC leaks are if theyre not at the intercooler ducts on top.

 

Dropped car off at the dealer and left the plugs with them. Tech said that if there was a leak of any kind, it would trip the CEL or there would be codes in IDS. Any truth to that?

Also what is the difference between reflashing the TCM & ECM and disconnecting the battery and if I disconnect the battery, what issues should I look out for regarding and systems that might need resetting or programming or does it all return to normal?

THanks again to everyone participating in this thread and offering their advice and expertise.

 

Always trip the CEL?........ NO! If that were always the case you wouldn't need guys like me! While that is the hope, as usual the 'real world' has other ideas! That being a dealer frustrates me, that's misleading.

Reflashing, reprogramming and reconfiguring are all different words for changing or updating software in a given module. That should really be reserved for real updates that actually change a software level. A level change is when an actual programming change has been made to correct some activity or decision the module is supposed to accomplish. By 'reflashing', certain things like adaptive values, fuel trims etc. are overwritten and therefore zeroed out, or returned to 'default'. Many times that is all someone is really trying to accomplish, clearing out adaptions; but many techs erroneously think 'reflashing' is the answer to everything. In the case of your '05 jahummer, disconnecting the battery will zero out your fueling adaptions, as would reflashing, but the reflashing is not NECESSARY to correct anything. I'd wager that there probably has been no correction/update to the ECM or TCM software in your car since maybe 2007 or 2008. And barring something turning up that terribly affects emissions on these cars, I seriously doubt they will ever revisit the module software, they have moved on to the current crop of vehicles.

So, after a battery disconnect, you will be concerned with a bit of driving to allow the fueling to re-adapt, resetting your clock and windows and that's about it. Disconnecting the battery WILL NOT wipe out transmission [TCM] adaption, that has to be purposefully reset by diagnostic equipment.

A word to N9921x, I don't think it is wise to be suggesting to folks they use something as volatile as starting fluid to check for air leaks. That is patently dangerous. I wouldn't want it on my head if someone lit up their engine compartment and was injured based on my suggestion. There are plenty of less volatile cleaners to use for that purpose. Just my opinion, you understand........

Cheers,

 

The ECM reflash was suggested to correct the sudden & substantial decrease in MPG and "correct" the roughness on cold starts. They think perhaps the throttle body replacement and Wynns cleaner affected the fuel adaptations. I did suggest the battery disconnect and was told that would clear the adaptations but not necessarily the idle roughness.

By the way, before the plugs, short term trims did occasionally go negative. I have not checked since.

The TCM reflash was to "fix" the notorious ZF lurch that only occurs when the shift mode is not set to sport, an issue that has persisted for a long time and was supposed to have been done way back when they did the fluid additive TSB.

 

Picked up the car today. Their Jaguar Master Tech said the plugs looked about 84K miles old although they do mostly warranty work and don't have occasion to replace spark plugs that often.

I drove around a bit and must say the plugs made a big difference with throttle response vastly improved.

As far as the ECM reflash he said not needed after he checked again, just suggested I disconnect the battery and reset adaptations.

I am holding off on the TCM reflash until I do the transmission flush.

I will also note I am not noticing the RPM bouncing up and down when stopped in gear.

 

Cool! Glad to hear you got such noticeable results. Those iridium plugs are really a godsend, but the change in maintenance interval from 60K to 100K for the supers was a crappy idea. They did that strictly as a sales tool, "Look how cheap your new car is to maintain for the first 100K miles"! Never mind they really can't be expected to last that long, at least, not as long as a normally aspirated car.

Also glad to hear he came around regarding the reflash.

Now sit back and enjoy the "new" feel of your XJ; I know you have a soft spot for that one!

Cheers,

 

jahummer,

Sounds like all Good News. Great stuff.

xrguy,

Interesting your observation about the plug life between the two engine versions. I'd like to hear your reasoning for this, very interested.

Cheers,

Languid

 

Boy, you guys always ask the most thoughtful questions......a guy has to collect his thoughts!

The change from platinum plugs to iridium roughly doubled the life of spark plugs. Thus what was a 30K change interval went to 60K in early V8 literature. [when the AJV8 was introduced the plugs were platinum] Before very long the iridium plugs came out and the maintenance literature was changed to 100K for the normally aspirated and left at 60K for supercharged.

Here's where it began.......

I asked, because iridium doubles plug life, right?? So 60K should have been a good interval in my book. The MARKETING DEPT. got involved and decided that to BE COMPETITIVE, they had to lower the total 'cost of ownership' for the 100K 'life' of the vehicle. [Thus my snide comment in the earlier post] So they tinkered with the maintenance intervals of certain things. NA plugs went to 100K, air filters went to 40K from 30K etc. etc. So there's that aspect. [Sometimes I hate Marketing folks]

There are also considerations that aren't readily apparent. Iridium gets you a long life electrode, but what about the OTHER SIDE? On an automotive plug the ground electrode is still steel, like it has always been. For years aviation plugs and of late racing spark plugs do have a harder platinum or iridium ground electrode as well, but not auto plugs; face it, people gripe about the cost of plugs as they are, nevermind the idea of having more precious metal in them. So erosion there is still an issue. Another point is the very small diameter of the electrode with iridium or some platinum plugs. The material is much harder, but being so small it also runs a way hotter tip temperature, and supercharging just aggravates that; the main reason I think 60K is about all I would expect out of plugs in a super.

I'm done rambling........


Cheers,

 

I wish Jaguar had not told me to wait to 100k on the plugs, as you say, I think 60k is about right.

I do have to correct you on one point though, both the IFR5N plugs I pulled and the Bosch I replaced them with have platinum grounds. When I spoke with NGK tech support they said the platinum gives them the 100k service interval, with just steel and iridium he said half that life.

The Bosch plugs were only $7 each less 40% coupon less mail in rebate made them a really good deal.

 

Please can you give the type number and source for these plugs?