Hey guys!

I just got a P0304 code on my 2003 Jaguar S-Type R with 73K miles on it. Rather than change out a single suspected bad coil, I decided to replace all the coils + spark plugs on the car.

My question is this: Where in the world do I buy these for a decent price? I know I want Densos Platinums but I was wondering what heat range sparks to buy? I'm looking for one or two levels cooler since I'm running an upgraded pulley and tune.

So here are the questions that I have for you wise folks

1) Which spark plugs to buy (heat range) and what to gap it to.
2) Where to buy a good set of ignition coils that won't break the bank but won't break my car.

I thank you advance for all your help.

Plugs: iridium NGK IFR5N10 and do NOT touch the tips at all. They are pre-gapped and damage if you even look at them.

Coils: you risk buying worse than what's in there. In case you do you'll have pain and may damage the cats.

Plugs are due at 100K miles so leave them in and I'd leave the coils in too. By all means buy one coil as a spare and keep it in the car. Get the right one.

Now, if you'd like to do things to keep your car going:

1. check the 2 bolts on trans side for trans shifter cable are there and snug (don't overtighten)

2. consider changing DCCV

3. get a cheap OBD tool (elm327 is great) with live data and learn how to use it to check for codes, plausibility of sensors and be sure to look at LTFTs

4. worry about the hose under the SC - read about it!!

5. consider changing coolant hoses as they're old and prevention is better than ...

6. check key physically opens door lock and boot (trunk)

7. check both keys do that and both fobs work

8. see what others say

What is SC ? Speed Control ? thanks

NA naturally (or normally) aspirated, SC supercharged or supercharger

See my signature which has a long list of ...

100k is manufacturer recommended based upon average driving and use, and to reduce cost of ownership in surveys, but all spark plug manufacturs tend to agree that plug performance degrades past 60k. I would change, but stay stock dont drop heat ranges youre asking for issues like carbon fouling. There are many out there with more boost and performance than yours running stock plugs and heat range without issue

In march of 2014 I picked up a 2003 one owner, dealer serviced, all records since new, 5K on a new 'dealer installed' ZF trans, Quartz in color, 112K STR. I too had ignition coil codes pop up...one and then one more.....the local, terrific dealer trained, indy said that the ignition coils should actually be changed ever 80 to 90K miles as they will start to pop a code 'under load' vs. every day driving.....simple.....auto zone, $48.00 ish per....vs. the dealer at $500.00ish per.

Next, plugs?....what where, price, etc.

After very extensive and indepth research I went with what I think in the OEM plug......what the heck? Jag puts them in!.....Here's the info....and yes, I bought them off of Amazon.

Denso SK16PRA11 Spark Plug
Sold by: vizionmotorsport
$11.29

No complaints.

As stated above, there's no need to deviate from the stock heat range.

Thanks! I'll definitely go that route and keep the wires stock. I'm just wondering, where I can get the coil? I've been looking everywhere for an OEM equivalent and am having trouble finding one. Or 8.

Thank you! I've already changed out my coolant hoses and reservoir. Changed the DCCV and trans cable when I serviced the trans and differential. Thank you so much.

Yes sir/ma'am. Seems like this is the common advice for me to stay within the stock heat range.

Thanks! I was wondering, did you change out all the coils? Or just one?

Gotcha. Thank you.

As to coil change out.....I changed them all out. Initially I had code pop up and with the help of my 'then' very mechanical neighbor and his OBD2 code reader found the problem....a malfunctioning ignition coil.....replaced it with the Auto Zone $48.00 ish, life time gar. one.....the next time the 'check engine light' went off (I'd bought my own code reader by then....about 5 weeks after the first incident) I saw the code....knew it was another ignition coil malfunction and then consulted the Indy where I was apprised that the 'realistic' preventative maintenance replacement on these (ignition coils) was as low as 80K and, really, no more than 100K ish.......what the heck. In for a penny in for a pound. I didn't want to 'dink' around with this one Saturday morning after another so, Yes, I replaced all the ignition coils at the same time, sans the first replaced one of course, and took that same time to install the new OEM DENSO plugs.

The entire job.......including faux pa's with tools dropping etc. took a some what patient 2 hours.....coils and plugs.

When it was completed I had performed a $585.00 ish x 8 (each) dealer ship maintenance (100K maintenance) in less than 1/2 a day for about $480.00 ish all parts included.

All in all not only a very satisfying day but a 'good day' as well.

Oh......I for got....this work was done on my 2003 S type R......112K at the time.

Just a 'by' line....this car was a one owner dealer serviced and maintained car with the original owners spending between $3,500 and $5,000 per year in maintenance.

I did put in a new from a dealer 'J' box shifter as the original one locked me out one Sat. am...thankfully in front of my work shop instead of 100+ miles from nowhere.

There were a couple on EBay for 1 to 2 hundred but with some calling around to different dealers up and down the state of California as well as internet and out side the state of California I found the best price for a 'new in the box' dealer part for around $675.00 or $750.00 ish.....What the heck the original one lasted 112K......and you never know where or what a used part has been through.

That being said....the actual failure in the 'J' box is a $35.00 or less solenoid that is replaceable in a newer (than 2003) 'J' box for less than $50.00 but not in the 2003 model. So if in 112K more miles this one, the one I bought dealer fresh, goes out then a $50.00 bill will solve the problem. Oh...and it's quite easy to install.

RE: ignition coil and plug replacement

YouTube has several excellent 'how to' video's......that's where my 'expertise' came from.

Agree with JagV8 on "Plugs: iridium NGK IFR5N10 and do NOT touch the tips at all. They are pre-gapped and damage if you even look at them."

Do not agree on the coil issue. Changing plugs in the 03 is an arduous task and if you are going to the effort to replace the plugs, I say replace the coil pack as well while you are in there. I do agree on keeping a spare coil just for the heck of it.