Spark Plug Change Interval - Boosted Coyote

crjackson

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I’ve been running with FI for about 15k miles now. I believe the plugs are iridium and gapped at 0.035”. They are the plugs that came with my Roush PHASE3 kit.

Today I noticed the idle note was a little off compared to the past year, and it got me thinking.

So what do you guys do for a change interval generally? Yes, I intend to pull them and have a look (sooner or later). Just wondering what everyone else does.
 
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redfirepearlgt

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annually. also you mean 0.035 which is a bit much for a tvs setup running 10 - 11 psi. depending on tuner with a similar setup i have been directed to use 0.026 to 0.028 gap. that said use what your tuner specifies.

best bet is go to the source...your tuner.
 

DieHarder

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I've changed to Brisk Silver plugs (>450 hp). Expensive, but zero issues since the change. Runs great. 0.032 gap I believe. About 8 lbs boost. Cost is worth it IMO. Just have to make sure you get the right plugs depending on the year of your car.
 

crjackson

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The tuner may have changed the gap, I was just posting how they shipped. I’m running 15 psi on my setup.

It takes weeks to see the tuner, so I try to get most answers before getting an appointment.

It’s been more than a year, so perhaps it’s time.

(I edited my 1st post to correct my decimal point error)

Thanks
 

Rich Grundza

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I’ve been running with FI for about 15k miles now. I believe the plugs are iridium and gapped at 0.035”. They are the plugs that came with my Roush PHASE3 kit.

Today I noticed the idle note was a little off compared to the past year, and it got me thinking.

So what do you guys do for a change interval generally? Yes, I intend to pull them and have a look (sooner or later). Just wondering what everyone else does.

I switched to E85 last fall and through the tuning process we found a number of issues, had missfires at 7.5k. Replaced the plugs as well as the wiring harness. (#4 injector was having problems traced to a slightly kinked wire) Anyhow, put in new plugs at the tme, NGK Iridiums and gapped at 0.028-0.030, which is what tuner recommended and several other coyote builders as well. 0.035 might be a bit much. and the plugs had about 15k on them. I'm running an EForce at 10.5 - 11 lbs of boost.
 

Juice

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I would suggest reflashing your current tune and see if it fixes the idle issue. I have seen mine do that when the tune wasnt quite right.
These copperhead pcms can get fineky. Atleast look at your LTFTs and see how much correction the pcm is doing.
 

crjackson

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I’ll be doing some work on her in a few days, and hopefully check further into this. It does sound however like it’s time to check/change the plugs. Although I did think iridium plugs would last longer. I didn’t realize that going boosted shortened the plug life so drastically.
 

crjackson

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Circling back to add info …
My tuner didn’t want to deal with checking or replacing my plugs. I pulled a couple myself, and they looked good. However, they were/are gapped at .035”.

The car runs well and I got side tracked, and did nothing … :(

Today I ordered a nice little gapping tool designed for dealing with these “Fine Wire” type plugs, and I ordered NGK6510 11-17 NGK 6510 LTR7IX iridium plugs. Hopefully that was a decent choice.

I haven’t decided if I shoot for .028” or .030” on the gap. Since it’s been on .035” gap for 41,000 supercharged miles, I’m thinking .030 should be fine.

IMG_3743.jpeg

I think my old plugs were Platinums. Here’s an example of how they look now. They are Ford branded CYFS12YP, and difficult to remove. It took about 70 ft. lbs to break them free. I was kind of shocked. I retorqued them to 12 ft.lbs.

IMG_1592.jpegIMG_1593.jpegIMG_1587.jpeg
IMG_1597.jpeg
 
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crjackson

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Same here, gapped at .028"
Installed them about 5-6k miles ago, in 2020, and I remember when I put them in I instantly noticed a smoother idle.
Awesome. I was a little concerned that since they come new with a .04x” gap, reducing it that much (to .028”) might deform (for lack of a better word) the ground strap excessively.

I also thought it might reduce idle smoothness. If it doesn’t make for a rough or erratic idle, then I’ll do the .028” gap.

Why in the world, did Roush go with a .035” gap to begin with? Was this an emissions compliance decision?
 

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