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DIY spark plugs

I’m going to DIY my next set of spark plugs (99 Accord, 4cyl) and I have access to the proper tools, a shop manual, and a competent friend to supervise me.

Any tips for a novice? What can I potentially screw up, and how can I avoid screwing up in the first place?


Replacing the spark plugs should be easy on the 4 cyl engine. Just apply a little anti-sieze compound to the threads of new plugs before they’re installed.



Clean around the spark plug bases to make sure no grit falls into the cylinders.

If they seem to be hard to get out, don’t force them. They may be seized, and you could mess up the threads in the head. Instead, soak them with penetrant and let it work into the threads.

Try to turn in the new plugs by hand, then with the socket in your hand, as far as possible. If you cross-thread a plug, it ain’t pretty…

The Accord has an overhead cam engine in it, so the way to start the new plugs going into the threads will be with the spark plug in the socket, attached to a long extension bar, but not the ratchet. Also, work on the engine when it’s cold so you don’t damage the threads when you remove the old plugs. Ideally, do the job after the car sat overnight. If that is not possible, the car should be parked for at least an hour before working on it. The engine should be cool to the touch before working on it. If you try to remove the plugs from the engine while it’s hot, you will probably strip the threads out of it, then you will really have a learning experience on your hands.

The advice I was given before my first time was to place a small-diameter rubber hose over the top of the plug, and use it to drop the plug down and thread it through the first 2-3 revolutions.

The thinking was that the hose could transmit enough torque to properly thread the plug, but would slip if one started to cross-thread.

You learned well weed hopper.


You’ll do fine. “access to the proper tools”? You need 2. A spark plug wrench and a gapping tool. Slack-jawed children of cousins have been doing this procedure for over 100 years, often for money. It’s neither rocket surgery nor brain science. Just one thing to remember:

Gap 'em, Danno!

(I’m pinching the bridge of my nose as I contemplate how many people have reached adulthood without changing even a lawnmower sparkplug. More whiskey please).

I think I actually changed a spark plug on my grandpa’s lawnmower when I was a teenager.

The one thing the braintrust of “seasoned mechanics” hasn’t mentioned yet (and I allowed all the time in the world to see if it would happen) is this:

Change one plug at a time. Never have more than one spark plug cable disconnected at a time. You don’t want to mess up the firing order.

I would suggest that when installing new spark plugs, you also install new plug wires.

Best of luck to you, Jeff

Al in MD

Awwww Zombie, there ya go again… ruining all our fun. We were hoping ol Jeff would be back later asking us what all the poping & banging & fire was from…
Seriously that was a good catch. I always do it, but would also have forgotten to tell him.

Nice try, I already knew to install one at a time. xD

Actually Jeff if you want to do a compression test you will have to remove them all, but you didn’t mention doing a c.t. so go ahead and r&r 1 at a time. If you decide to do a c.t. mark the wires with some tape.

You also have to do that if you’re going to rebuild the engine or swap in an entirely new/rebuilt engine. If you’re going to convert the car to electric you’d need to do that too.

That having been said, labeling the wires strikes me as the kind of thing you think about when it’s too late, so good catch.


Plug wires SHOULD last the life of an engine if properly maintained. Clean them periodically with a damp cloth and they’ll last for-ever…My wife’s 96 Accord plug wires lasted 10+ years and well over 200k miles…Never a hickup.

Take A Close Look At Those Wires. All My Cars Have WoofProof Wires ! They’re All Factory Numbered. I Live On The Edge And Pull Them All At The Same Time.


They were replaced the last time the plugs were replaced. They only have 30,000 miles on them.

Biggest thing I see that kills plug-wires is DIRT…When plug wires get a buildup of dirt and oil…they hold moisture…This moisture on the wires can cause arching…A couple times a year just wipe the wires down with a damp cloth followed by a dry cloth keeps the wires clean…and you’ll probably NEVER have to replace them…Although very few cars built these days have plug wires anymore…Most use a distributor-less system

I loosen the old plug about a turn, then use a blow gun to clean out the plug well. That way, any dirt comes up and can’t fall into the cylinder.