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Discussion Starter · #1 ·
After getting the oil done this morning at the world famous Harix's in San Gabriel, I decided to try to change the plugs on my own. So, while I was in there, I took a few pics so the rest of you can decide if it's something you want to try.

First getting to them, a bit of a J O B. You need to remove the trunk carpet, net, and trim only to find the access panel basically glued on by double sided tape after you removed the bolts. A little tugging/prying, and it comes off.

Then, you'll notice a bracket over one of the coil packs? Yeah, because getting to them wasn't hard enough already. Luckily, the bracket comes off and goes back on very easily (I think it stabilizes/secures the intake plenum from what I could gather).

Once you get to them, process is fairly straight forward. I did them one at a time, hand tightened each, then added about an eighth to a quarter turn after that (too lazy to get a torque wrench out and check each one). While each coil pack was out, I cleaned them with an air compressor and cleaned all the contacts.

Overall, not a bad job and found the top three plugs actually harder (awkward reach) than the ones you get to from the trunk panel. Once that panel and the crazy surprise bracket came out, they were actually easier.

Oh yeah, almost forgot, changed my K&N air filter (I have two so I don't have to wait for it to dry when I scrub the heck out of it) while I was in there and checked on my Shorai which still looks brand new!
 

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Discussion Starter · #2 ·
Here are a few more of what the plugs looked like. The gunkier looking ones were the bottom three and first to come out. I did the top three last given I wanted to make sure I could get to the "hard ones" first!
 

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Those plugs were 99% like new still. They say 100K for a reason. While you had fun doing it, you will see 0% improvement. Just being honest. Did my Elise after multiple years of track duty and expected a better running engine. Just didn't happen. Spark plugs are ALMOST getting to be a life of the vehicle item.

The highlight is the picture with the panel removed. Gotta put that one in the memory banks! Also 50K.. Well done, she's broken in now!
 

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Illegal Alien
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How did the old gaps measure vs spec?
 

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Discussion Starter · #6 · (Edited)
Those plugs were 99% like new still. They say 100K for a reason.
BRG, actually Lotus (Well, their service booklet that comes with the car's manual anyway...), says 54K. Hence my rationale to change them.

However, I will say, I am the guy that changes the oil every 5k, the K&N air filter every 5k (I have a spare ready to go every time), brake/clutch fluid every 20K (service booklet says 18K), transmission fluid/gear oil every 30K, and pretty much follow or exceed everything else in the service booklet. As you can see from my mileage, having owned the car for just over 2 years, I do drive it occasionally. So, I like to ensure it's always running at it's best.
 

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Discussion Starter · #7 ·
How did the old gaps measure vs spec?
Julian, they were pretty much spot on which was nice to see. I will say the bottom three (access panel plugs), were notably gunkier than the top three. And there was one (the last one under the surprise bracket), that was notably the gunkiest.

Seemed to be more of an issue of oil seeping up through the threads (not torqued properly???) as all had nice clean (slightly carbonized) firing/igniter tips.
 

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This was on my list of things to do.

Has anyone come up with a reason not to use OEM plugs? I haven't changed them in a car in a while but if I recall correctly, changing type (copper/iridium/plat) might mess with resistance and throw misfires?
 

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Discussion Starter · #9 ·
Plack, I did a little research before buying my plugs. Most opinions were that you should stick with the factory iridium. Then the debate shifted to NGK versus Denso. At the end of the day, I went with Denso, since all I had to do was drive to my local Toyota dealership. The parts guys were cracking up when they saw my "Toyota".
 

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Lotus says 54K?? WOW< I haven't seen a vehicle under 100K in a decade now!!
 

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Discussion Starter · #11 ·
Don't make me say it BRG... RTFM! Just kidding! I was a little taken back on the service cycle as well, but who am I to argue with Lotus engineering. Also, there was no way I was going to pay Lotus upwards of $700 for this! BTW, it's not all labor. They charge like $50+ a plug!
 

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Know the manual pretty well, was just shocked at this one. Only made it to 34K on Elise, and 12.5K on first Evora! so I never got to those service lines.
 

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Nice write up! This will come in very handy since I always change my plugs well before they're due. Thanks for this thread! :clap::clap::clap:
 

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I suggest marking each old plug w/cylinder #.

If a problem arises later, you can go back and see the "history".


I carry a spare old set in the car with some tools.
 

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Disciple of Chapman
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Awesome right up. thanks :up:
 

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Discussion Starter · #17 ·
No worries guys. I know the pics and explanation go a long way for people trying to figure out if they want to take the project on.
 

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As to hunky threads, I and really not sure of the source. You mentioned oil seeping (welting/wicking) up threads from cylinder chamber. Honestly I would be surprised of this as a source, implying lots of oil ring blow by. More likely gunk outside of engine building up, especially on the hidden rear bank, sweeping done into plug well and coating the treads as you unscrew the plugs. What leads me mostly to this conclusion is the solids on the treads of the aft bank. This stuff would not come up from within the cylinder, but rather looks like a collection of oil, dirt grease accumulated on the outside.

Good to hear no gap deterioration. As to 100k plug service, I can understand lotus cutting that basically in half. 1st they are running engine harder than Toyo service and second I normally cut service intervals in have from OEM. Goal of OEM is to get you through warranty period, including emissions period of 100k on many of the emission components, they really don't care if your engine blows up at 102000 miles they also don't care if power output is down by 20%. Whereas we as sports car owners do on all accounts.
 

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Not that we all have dynos in our garage, but I'd love to see the REAL effect of a new set of plugs on any car for that matter. Is it significant or 1hp tops???
 

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Discussion Starter · #20 ·
@ Julian, yeah mine was just a thought/theory. Again, as seen in the pics, the plug condition was pretty good sans the gunk on the threads of the aft/bottom three.

@ Brg, not sure about the plugs, but I will say, the car was notably stronger, but it always feels fresher when I do the oil and air filter together. Perhaps the plugs added a bit too.
 
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