Spark Plug Replacement - Help
 

I'm at the point where I should change the plugs in my XJR and have run into a snag: extracting the coils. I can only get 3 of 8 to slide out.

Is there a trick to this?

Oh, and in case anyone is curious, the original plugs are NGK iridium. I've got a set of Bosch iridium at the ready once I can figure out how to extract the darn things.

The boots can bond with heat and oil film. If that is the case, you might need to do some careful wiggling and twisting.

Now, about the Bosch plugs ... there have been reports that the tips are too long. You might want to check that carefully for yourself.

Re: Coil Boot(s)
 

Be careful, slowly twist back & forth else you'll need new coils! You can try a LITE spray of WD40 easing the straw into the channel then twisting slightly back & forth! Be PATIENT!!! Before re-installation lube the boots with di-electric grease! We always used this procedure with Direct Ignition Cassettes to prevent this issue as well as Arc-Over in the SAAB Services!

if you have an air compressor and an unrestricted modified air blower with around a 10" 1/8 or 1/4" tube extension you can try this: insert the blowers tube down into spark plug area and give it a couple of sprays of air.the blasts will hopefully break the seal of the spark plug boot. i have had good luck with this procedure on some cars(have yet to try it on a jag though), so long as you can snake and squeeze the tube past the coil and down into spark plug area it may work for you. a long dull dental type u-hook or L pick can also work provided you can get it past the coil. idea is to catch the bottom of spark plug boot and break the seal/vacuum/stuck by pulling at the base of boot with pick.oh, and dont forget to twist and pull at the same time.

Okay, so maybe I didn't describe this adequately, so let me try again:

There is not enough clearance between the engine and the fender to pull out the coils on 5 of 8 cylinders. They are not stuck; there simply is not enough room to pull them clear of the head.

There must be a trick to this.

Thanks again.

i have changed these plugs over 20 times...I understand the clearance near the firewall. .its tight but pull the back coils directly up and tilt slightly towards the front of the car...after its disconnected...the real trick is extracting the plugs. ..i use a 3/8 2 inch adaptor with a swivel head 360 degree screw ratchet..once the plug has broke free remove the ratchet then use a 3/8 inch 5 inch adaptor to unscrew with your hand...if the plug has pooling in which i check with mirror scope...I blow the oil out first with a air line then use a 24" grapple tool by craftsman.at times you can use a your magnet catcher...if you wish to see pictures of these tools let me know i can send to your email...also make sure you remove the oil dipstick for the driverside also for clearance of the coil

let me add also...please use the ngk iridium plugs....i can tell you from experience that you wont get the longevity out of the plugs or performance if you downgrade..I have seen several people try to use platinum plugs because the iridiums are costly...but the platinums file out or cant handle the heat thats generated..The porcelin will crack and or turn brown wihcih is sign of overheating.

I'll be a little bit more determined, I guess, in removing the coils. I just didn't want to force something that would result in a greater-than-necessary replaceemnt expense.

An earlier post mentioned depth of the Bosch plugs. Side-by-side comparison shows them to be identical to the original NGK.

And, yes, putting in standard or platinum plugs would be mistake. Theconsistant performance over the life of the plud is critical. The last thing this engine needs is misfire or pre-ignition. That could get very expensive, very quickly.

Thanks again.

RCsnyder I think you will be fine my friend....if you need anymore help on this car let me know..

I'm having some trouble with this myself, mainly on the driver's side where the oil filler and dipstick are. There are several hoses and tubes which crowd the area and I can't seem to get the panel off with disconnecting them, however I have no idea what these tubes and hoses are and how to properly disconnect them. Are there any tips or tricks?

xj8xr yes thats the most difficult side,but takes a little finess...remove the oil dipstick,then the coil coveres,the lines are the brake booster line that feeds into the master cylinder and the regulator line...one feeds into the throttle body pressure plate attached to the rear of the supercharger.The firewall cowl which is the plastic housing running alone the firewall does not have to be removed..the most difficult coil is the rear coil..make sure you bring her straight up while at the same time tilting her towards the front of the car,she will come out...Let me add,the iridium plugs burn less current than the platinums to produce spark...I always get mine from ebay or the dealer,they are around 85.00 from ebay and 140.00 from the dealership if i am in a rush to do a car...Keep us posted guys thanks

I have been using Bosch in my XJS 4.0, XJ6 4.0, XK8 4.0 & S-Type 3.0 for years without a problem. If the plugs I installed were to reduce the performance of the car I can assure I would replace them quickly. The key to this is using the proper plug for the car and gaping the plug properly. The choice of the plugs you want to use is yours just be sure you use a quality plug and torque it properly to factory specs when installing them.

It's time to change the spark plugs; in following this thread I'm now confident as to the proper plugs to install. The process seems quite straight forward once the plastic valve covers are removed. My issue is, I'm hesitant just to rip the covers off and I can't find any clips or screws for removal of it! It's a mystery to me.

Can anyone shed some light on the proper removal of the covers, so i don't rip or crack it?

Thanks for any instruction you can forward>

A slight twist and pull and it will come out. This link might help JagRepair.com - Jaguar Repair Information Resource

A few photos of the underside of the covers. Pull up to disconnect the plastic snaps.

Thanks - The photos really help to understand what's under there!

It looks as though a good swift PULL should do it! Any chance of breaking those two little plastic clips?

And I thought you were looking for a way to remove the plug coil pack. Sorry! I see I need to pay attention to what I am doing….

If you pull or pry straight up, they should be ok. The third time I removed them, I slipped and pushed it sidways....I had to purchase a replacement. The photos are of the broken covers. They can still be used but I got new ones.
:icon_jammin:

Some photos of the Ignition Coil.

We'll, getta go....

Well, it's done! I replaced the plugs with NGK IRF5N10's. It became a little confusing as to just what the GAP should be. My manual doesn't say and JTIS does not mention the GAP for the 4.2 engine.

NGK say don't adjust the factory setting but frankly they were not consistant, so I adjusted them all to .035. I did see somewhere, that the gap should be between .035 and .039.

Does anyone exactly what the GAP should be and what is the effect of too narrow of a gap?

Beyond that the job was quite easy to perform!

Thanks!