Topic: Lesson Learned: Reddit Posts Show Why Spark Plug Changes Are Best Left to the Pros

[AutoTrader.ca]

A shoddy spark plug job can end up costing you thousands in repairs.
Read more...

[rrocket]

I guess Pritchard doesn't do his own apart plugs.

[EV Dan]

So, while the physical process of changing spark plugs is a relatively simple “unscrew, remove, reinstall” procedure, do-it-yourself types should not underestimate the precision required at every step of the job, including the selection of spark plugs themselves, and the proper procedures required to replace them. A lot can go wrong, and if you’re not positive that you know what you’re doing, it probably will.

If in doubt, leave this job to the professionals.

There is a video on YT where a dealership technician changes spark plugs. He DROPS each spark plug down the cylinder head and is likely thrilled with his channel click numbers, or not... Talk about bent electrodes and trusting the "pros".

I will take my DIY chances thank you very much.

Fun fact. Over a decade ago I had replaced spark plugs in a V6 F150 with Bosch ones from Crappy. Obviously looked up the correct type. They were those multi-electrode ones. Guess what, the electrodes melted completely within a couple of months. Ever since I go OEM, NGK or Denso, and not the ebay kind 

[Firm]

I'd much rather see an article with some tips/guidance for DIYers on how to do the job correctly and avoid costly mistakes, than trying to scare everyone off the idea of working on their car.

[rrocket]

I'd much rather see an article with some tips/guidance for DIYers on how to do the job correctly and avoid costly mistakes, than trying to scare everyone off the idea of working on their car.

Yep.

[Arthur Dent]

How does one even drop a plug down into the cylinder head? If the thread is intact its bigger than the hole no?

[Great_Big_Abyss]

How does one even drop a plug down into the cylinder head? If the thread is intact its bigger than the hole no?

I was wondering that myself.

[bridgecity]

This article is full of worst case scenarios/hyperbole, as in the quote below.  I normally like Justin's articles but this one is over the deep end. 

In modern engines, replacing spark plugs is a high-precision job: Worn-out spark plugs must be replaced on a preset schedule using a specifically designed plug of a very specific size, shape, and layout.

Also, the new plugs need to be fastened into the cylinder head using a precise amount of torque for proper fitment, vital to engine performance, efficiency, and the long and healthy life of the spark plugs and all associated components.

With the precise tolerances of modern engines, there’s no room for error when it comes to changing your plugs. For this reason, it’s a job that’s best left to the pros.

   This line of thinking wouldn't have anyone changing a light bulb in their house.

[ktm525]

He's referring to dropping the plug down the deep hole on OHC engines. Don't touch! lol. Ridiculous crap.

[PJungnitsch]

I'd much rather see an article with some tips/guidance for DIYers on how to do the job correctly and avoid costly mistakes, than trying to scare everyone off the idea of working on their car.

That would be much more helpful

-when removing, loosen the plugs a turn and then use compressed air if possible to clean around the seat
-thread in by hand initially, to avoid cross threading
-plugs need to be tight but not overly so, take special care with aluminum heads/reinstalling used plugs/taperseat plugs with no gaskets
-avoid purchasing spark plugs off Ebay/Amazon, as counterfeits are a problem

-get a garage to do a F150 with the 'easy break' plugs 

[Dante]

I'd much rather see an article with some tips/guidance for DIYers on how to do the job correctly and avoid costly mistakes, than trying to scare everyone off the idea of working on their car.

That would be much more helpful

-when removing, loosen the plugs a turn and then use compressed air if possible to clean around the seat
-thread in by hand initially, to avoid cross threading
-plugs need to be tight but not overly so, take special care with aluminum heads/reinstalling used plugs/taperseat plugs with no gaskets
-avoid purchasing spark plugs off Ebay/Amazon, as counterfeits are a problem

-get a garage to do a F150 with the 'easy break' plugs 

I'd add:
- use proper tools - some are generic but some may be specific to application - don't improvise
- research in advance torque specs for the plugs in your application

[EV Dan]

How does one even drop a plug down into the cylinder head? If the thread is intact its bigger than the hole no?

I was wondering that myself.

There is like a 6" drop before the spark plug reaches the threaded hole. If dropped in as opposed to being lowered with a spark socket wrench, there is a certain chance of smashing the ground electrode, like shown in one of this this article's pictures.

Anyways, there is a Toyota tech suggestions on how to do it right:
https://www.youtube.com/watch?v=IAb9b3Hrea0

[WP v3.32]

change quite a few plugs in my days as well as glow plugs.   just don't be dumb. 


Elbow tight , that's it.    never had issues.

[ktm525]

I like to use a torque wrench or follow the plug's recommendation. Typically NGK is a 1/2 turn on gasket plugs while tapered seat is about 1/8 after plug seat has made contact with head.

I don't use anti seize on plugs but again ngk says if you insist to back off torque value by 30%.as that will lead to over torqueing. Don't get ham fisted with aluminum heads.

[EV Dan]

Do you guys disconnect a battery when changing spark plugs?   

[Arthur Dent]

I haven't in the past ... maybe I am doing it wrong.

[Firm]

I don't either. But, it's a safety thing...If you read the manufacture service manuals for just about any job, the first thing they tell you to do is disconnect the battery. Minimizes risk of injury, and damage to the car.
I hate disconnecting batteries because of all the re-learn stuff, so I avoid it if possible. I understand the risks though, especially in newer cars....remote starters, keyless ignitions, electronics that never fully shut down, etc.

[rrocket]

I don't either. But, it's a safety thing...If you read the manufacture service manuals for just about any job, the first thing they tell you to do is disconnect the battery. Minimizes risk of injury, and damage to the car.
I hate disconnecting batteries because of all the re-learn stuff, so I avoid it if possible. I understand the risks though, especially in newer cars....remote starters, keyless ignitions, electronics that never fully shut down, etc.

All that being said....

I think the risk is quite low.

YMMV.

[Fobroader]

Talk about a mountain from a molehill. I've done the sparkplugs on my FIL Journey like 3 or 4 times, its about a 10 minute job with basically 0 chance of screwing anything up. I mean, if you are afraid of screwing up firing order, go one at a time but with most modern cars being coil on plug, thats damn near impossible. Please don't scare people away from DIY'ing simple stuff on their cars with all these imaginary boogeymen, its not that hard.

[EV Dan]

I don't either. But, it's a safety thing...If you read the manufacture service manuals for just about any job, the first thing they tell you to do is disconnect the battery. Minimizes risk of injury, and damage to the car.
I hate disconnecting batteries because of all the re-learn stuff, so I avoid it if possible. I understand the risks though, especially in newer cars....remote starters, keyless ignitions, electronics that never fully shut down, etc.

All that being said....

I think the risk is quite low.

YMMV.

I've never done it either. My take on it is if the doors are locked and the key fob is away, there is no chance anything would try to fire up.