Re: Spark Plug questions

I've done most of the maintenance on my vehicles for many years. However when recently I changed the plugs in my 2000 Box S I had 2 plugs where the ceramic insulation cracked. That results in a low speed miss that goes away after accelerating past 3K.

Is spark plug quality going down? The 2 victims were NGK and Beru. Am I getting too strong? That I doubt. When I installed them I used a torque wrench and went to (I think) 22ft. lbs. and it felt about correct for that torque measurement. For the future I'll go back to snug and one tug (which is probably around 16 ft. lbs.). Anybody else experience this?

Quote
MarknearChicago
I've done most of the maintenance on my vehicles for many years. However when recently I changed the plugs in my 2000 Box S I had 2 plugs where the ceramic insulation cracked. That results in a low speed miss that goes away after accelerating past 3K.

Is spark plug quality going down? The 2 victims were NGK and Beru. Am I getting too strong? That I doubt. When I installed them I used a torque wrench and went to (I think) 22ft. lbs. and it felt about correct for that torque measurement. For the future I'll go back to snug and one tug (which is probably around 16 ft. lbs.). Anybody else experience this?

No. Quality is fine. Or there would be a blizzard of reports of plug breakages.

Tightening spark plug should not put any stress on the insulation. What can happen is one gets sloppy with the wrench/socket and during installation tilts the socket and the plug can't take the side load.

My advice is to follow the factory spark plug recommendation and the factory spark plug torque recommendation and be careful. While the plugs can withstand thousands of hours of engine run time with nothing more than some electrode erosion they can't take any brief side loading when being installed.

That there were two brands in there and maybe some maintenance was delayed. Perhaps after way too many heat cycles the ceramic was stressed out and ready to go anyway. Also, I imagine some plugs are more awkward to get at, thus having more to do with the breakage than brands.



Edited 1 time(s). Last edit at 03/25/2016 03:50PM by Laz. (view changes)

Both of the plugs were new. I was replacing the ones that were in the engine - 60K maintenance. As to the 2 types of plugs. I ordered Beru's but was shipped NGK's. I returned the NGK's and was shipped the Beru's. I installed the Beru's and immediately had a low speed miss. I replaced the coils, removed the Beru's and put in the latest and greatest coils and new NGK's (did not want to wait another week for delivery, NGK's in stock at my Autozone). Again I had a low speed miss. Parked the car for the winter and later ordered a Durametric (along with the BoxS I have a 993tt and a 991 club coupe). Come this spring I "exercised" the Boxster until I could get the check engine light to come on. Durametric said ignition problem on cylinder #2. I removed plug #2 and replaced it with one of the five remaining Beru plugs. Engine runs great now. FYI both the Beru and NGK plugs have the same depth, are heat range 6 and are 4 prong plugs. This car is more of a summer cruiser so it doesn't see a lot of high speed work or anything north of 6K rpms. What makes it even stranger to me is that the cracked plugs were installed in cylinders 2 and 5. These are the middle cylinders and are not hard to access. I could see torque problems if these plugs were in the front cylinders but the middle ones are easy - its a straight shot. And BTW I hand thread the plugs until they bottom out and only then do I use a wrench for the final setting (and with the Beru's I thought I'd be extra careful and use my 3/8" torque wrench set to 22lbs which is the factory spec as I recall).

NGK is not on the list for Boxster spark plugs.
Only listed are Beru and Bosch.
Make sure to get the correct temperature for the car.
Different model years have different temperature requirements.
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

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"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

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For starters, i have noticed no degradation in quality. If anything, electrical and other parts have improved in quality over the years.
They truly don't make them like they used to, thank God.

But heat cycles and vibration do take tolls. Plus, who knows how they might have been treated in transit -- or even by you. Box dropped?

I'm typically amazed at how well they last - especially the fowling part with today's tight mixture control. I only change them because i use the car(s) for competition. On the street i doubt i'd EVER have to replace them.

Bigger issue - watch the coilpacks for cracks and misfires.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

Edited 1 time(s). Last edit at 03/27/2016 12:42PM by MarknearChicago. (view changes)

Quote
MarknearChicago
I've done most of the maintenance on my vehicles for many years. However when recently I changed the plugs in my 2000 Box S I had 2 plugs where the ceramic insulation cracked. That results in a low speed miss that goes away after accelerating past 3K.

Is spark plug quality going down? The 2 victims were NGK and Beru. Am I getting too strong? That I doubt. When I installed them I used a torque wrench and went to (I think) 22ft. lbs. and it felt about correct for that torque measurement. For the future I'll go back to snug and one tug (which is probably around 16 ft. lbs.). Anybody else experience this?

Maybe I'm misunderstanding. Are you saying you used 2 different brands of spark plugs?