Coil Pack/Spark plug Question

[Jolbaru_LGT]

So, in doing the timing belt, I've got 4 rusty looking coil packs. It's not giving codes or anything, but the old spark plugs were toast. They were hugely gapped beyond .30 and charred white. They were the NGK 93420 Ruthenium HX plugs. Which were probably the wrong ones, right? Anyways, from the pic, are the coil packs shot? I'm sure they are original w/222,000 miles.

 

Only option I see to replace them are dealership coil packs for 75 bucks a pop. Might be a good idea to do them while the car is still apart? Thanks in advance.

 

Oh, and the old plugs were almost impossible to get out. Like, it took 150 ft lbs just to get them out. Maybe anti-seize was used? Idk, but from what I understand, I now have to clean the holes out with an old plug, or with a cleaning threader..

[NORULZleggy]

Go to rock auto and get 4 new plugs and get intermotor coil packs. the are 60 a pop. when my 09 WRX had issues, I bought 4 coil packs for less then 200 with a coupon. They ran GREAT, and they are made in japan or Germany. use the Iridium plugs also. You will be set them. depending on the miles, I would replace them. That's just me.

[ScottFW]

Used plugs should have a bit of light brown crust/char on them. Google image search for "reading spark plugs" to see what's normal and what's not.

I don't know if the Ruthenium plugs are "wrong" or wouldn't work properly, but the correct plugs are NGK Laser Iridium SILFR6A. I've never used anything else. They usually come properly gapped but I verify before installing.

Use anti-seize on the threads and see how well they thread in, and don't over-torque them. I like to avoid chasing threaded holes where it could result in debris getting into the cylinder. Unless the old plugs came out with bits of cylinder head stuck between the threads, you're probably fine.

 

That coil pack maybe looks a bit more rusty than mine, but coil packs aren't in need of replacing unless the car is actually misfiring. Weak coils usually misfire under load first (which you would definitely notice) especially if the spark plug gap had grown too large on old plugs. If you're getting some rough idle, there are several other possible culprits (gummed up fuel injector/s, TGV o-rings, burned valve, pistons/rings). However, you could use RomRaider to monitor roughness counts per cylinder, and swap a suspect coil to another cylinder and see if the roughness moves with it.

[Jolbaru_LGT]

One of the plug’s white porcelain cracked when coming out. They were seriously stuck in there. It took a stupid amount of force to get them out. I blew out the porcelain as best I could with air before removing the cracked plug. I’ve never had plugs stuck in there that bad.

 

Anyways, would a misfire be obvious? Or throw a code? My budget would rather put all the coils back in and only change them when needed.

 

I do have the correct plugs you’ve mentioned. But I’m hesitant to put them back in if they require that much force. Someone mentioned a threaded cleaner plug. I’ve also heard anti-sleaze would react and mess up the threads on an aluminum block. Someone said don't use it. Confused here.

[ScottFW]

Anyways, would a misfire be obvious? Or throw a code?

Yes and yes. Misfires will trigger a CEL and one or more fault codes that clearly indicate a misfire.

 

I’ve also heard anti-sleaze would react and mess up the threads on an aluminum block. Someone said don't use it.

"Someone" may not know WTF they're talking about.

The whole reason anti-seize exists is to prevent threaded steel objects like spark plugs from galling and sticking and damaging the threads in aluminum holes, like the ones in your cylinder heads.

Skip it and you will eventually get to learn how to install a helicoil.

 

When you first put the plug in the hole, turn it CCW (backwards) by hand until you feel the little "click" that indicates you have the threads properly lined up so you don't cross-thread them, then go CW/forwards. The new plugs should not resist much for the first few turns when threading them in by hand. If they require a crap-ton of force, the holes could already have been cross-threaded, perhaps by the same genius who neglected to use anti-seize. Some people should not work on cars.

[Max Capacity]

FWIW, my wagons coil packs have 277,500 miles and still work fine.

 

My old plugs came out nicely with the small dab of anti-seize on them, the new ones I put in a few months back also had a small dab of anti-seize.

 

I put the stuff on every nut and bolt I put on my cars. Even the lug nuts. Been doing that since the early 2000's when I had a hard time getting a lug nut of my 2000 GT wagon.

 

If you want go to a local auto parts store and ask for a spark plug tap, I seem to recall its the same as an O2 sensor tap. Run it in the hole and make sure you get all the metal shavings out if any are made. Put a little grease on the tap, it should hole must of the particles.

Edited July 26, 2019 by Max Capacity

[utc_pyro]

NGK 93420 plugs cross reference to LFR6BHX's which are the correct plugs for the car. Those are the Ruthenium version of the SILFR6B8 Iridium plugs used on the '10+ LGT, which are upgrade plugs for our cars. They have a slight difference at the tip that speeds up the flame front by some trivial amount, which can result in less knock tenancy. They were only available on the US market about a year ago, so unless the previous owner imported them from japan they probably were changed recently.

 

For coils, OEM Diamond Electric are best but some of us have had OK luck with Cosmos racing coils for half the cost. If they aren't misfiring, there isn't any point in changing them.

[Jolbaru_LGT]

Yes, my bro must have changed them when he did the clutch. They were trashed, meaning the coil packs were garbage. I’m going with OEM Subaru coil packs at 75 a pop.

[Infosecdad]

Yes, my bro must have changed them when he did the clutch. They were trashed, meaning the coil packs were garbage. I’m going with OEM Subaru coil packs at 75 a pop.

 

Consider the NGK coil packs from Rock Auto at $60 per.

They are made by Diamond as well.

[Jolbaru_LGT]

According to NGK you shouldn't use anti-seize on aluminum heads, that their plugs have already got a factory coating to prevent seizing up. But, from what I've read, if you're re-installing plugs you should use a bit of anti-seize. Edited July 28, 2019 by Jolbaru_LGT

[Tehnation]

if it ain't broke, don't fix it! I'd get one coil pack if anything, just in case.... and keep in the trunk with my car medical kit.... lol, i tend to spend a lot of time on the side of the road.... u can get to the coils with simple 1/4" ratchet easily.

 

Use a torque wrench if you don't know what 15-20 lbs of tq feels like..... people tend to overtighten the spark plugs because it goes where explosions happen lol.... not true... don't over tighten your spark plugs or u might end up in a situation like this...

[Jolbaru_LGT]

if it ain't broke, don't fix it! I'd get one coil pack if anything, just in case.... and keep in the trunk with my car medical kit.... lol, i tend to spend a lot of time on the side of the road.... u can get to the coils with simple 1/4" ratchet easily.

 

Use a torque wrench if you don't know what 15-20 lbs of tq feels like..... people tend to overtighten the spark plugs because it goes where explosions happen lol.... not true... don't over tighten your spark plugs or u might end up in a situation like this...

 

I think it was broke. All the coil packs were rusted out and swollen. All of the newer style plugs came out charred white and hugely gapped. The car was probably misfiring, but I guess I’m not the best judge of that. All I know is that it seemed to lag under power worse than my old Volvo 240. Lol. I’m pretty sure I made the right call.

[Tehnation]

i thought the issue was the spark plugs? obviously change those. did you test the coil packs at least?

[Jolbaru_LGT]

i thought the issue was the spark plugs? obviously change those. did you test the coil packs at least?

 

I did not test them. I just don’t want to replace them if/when the time comes to either change the plugs (60-80,000?) or do the timing belt (100,000) based on the look of them, I’d rather change them while it’s all apart and the engine is in the air. One coil actually looked decent, so I’m saving that for a spare. I did change the spark plugs, but they shouldn’t have been trashed after I’m guessing about 20,000 miles.

Edited July 29, 2019 by Jolbaru_LGT