Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Can a new spark plug be bad right out of the box?

Apparently it can. A post here by the owner of a 2003 Trailblazer replaced his spark plugs and got a misfire code. Turns out one of the new plugs was bad.

And here’s a quote from a guy on a Ford forum about finding a new spark plug with no electrode:

" My wife’s brother is an auto-mechanic, and he showed me a spark plug when I was in his shop. He kept it in his toolbox as a constant reminder to check the simple things that no one thinks to check. The person’s vehicle in question did what you did and brought it to several different mechanics, and even had several mechanics at the dealership (where he worked) look at it and couldn’t find anything. Finally, he thought to look at the spark plugs and one of them actually was hollow. After he disassembled the spark plug, the internals were missing. It was just a bum spark plug, but who would ever think to check it when it looks fine from the outside?"

Has anyone else come across a bad ( new ) plug? Which brand was it?

Yes. I don’t remember the brand, but the ceramic insulator was broken on one plug right out of the box one time. Parts house changed it with almost no problem.

Some 30 years ago when I worked as a mechanic we bought a whole bunch of Champion plugs for our tuneups…One tune-up on a V8 - I went through 12 plugs to get the vehicle running correctly. That was repeated several times over next few weeks. We through them out and went to AC plugs…Never had a problem again.

I haven’t had a problem with plugs since then. I’ve been using NGK plugs since I started buying Nissans, Honda’s and Toyota’s some 25 years ago. Never had a problem…but then again I’m only doing my vehicles once a year…not doing tuneups several times a week…so my sample is very very small.

I ran across a bad from the box spark plug situation 3 times in about one month. As a mechanic, that eats up the valuable commodity called time and the money associated with it.

In all 3 cases the plugs were Champions and the 3rd incident led me to never use a Champion plug in a car again. In two of the cases the plugs were misfiring badly from the get-go and in the 3rd example the engine would have to run about 40 or 50 miles before the plugs would start misfiring.

In one other incident many years ago I ran across a car on which one of the 8 AC spark plugs had apparently died within a few miles but there was a bit of a story behind the car so I don’t know if the plug was the cause or a symptom. The prior 2 week car history was very convoluted.

Other than those, never a problem with any brands.

Yes. I have a couple of them that made it past quality control with no threads. If something that obvious gets by then anything is possible.

There are defective plugs, shelf damaged plugs, plugs that are not up to the original specification and plugs manufactured to a specification that has been superseded by the automobile manufacturer. Using the manufacturer’s specified plug is always worth the price and trouble. I have seen manufacturer’s bulletins specifically naming plug brands as being problematical and on one occasion the manufacturer specifically instructed dealerships to remove the factory installed brand and replace it with another brand to eliminate customer complaints.

Certainly. I’ve seen bad brake shoes out of the box, bad body control computers, bad ignition coils, and yes bad spark plugs. Anything can be bad out of the box. Nothing is perfect.

You know what new means? Never Ever Worked.

Ford had a rash of those when they first came out with that funky long plug in the 5.4.
We soon learned to look at every plug in every box with a magnifying glass to look for hairline cracks in the ceramic ( clean new plugs are hard to see cracks, they probably cooled them too fast )
We put every one on a full pay warranty r.o. and they soon got the message, the part number was revised and we havent had much trouble since. ( we didn’t just swap out bad parts for good. who would ever know ? The r.o. paid as though it had been completely installed to find out it was bad. )

Spark plugs are so functionally simple, I assumed every factory would test each plug, but apparently not.

Manufacturing technology, process control and quality control methods are so good these days that a simple thing like a spark plug coming out of the factory with no threads or no electrodes just should not be happening.

Inspection costs money especially when you make millions of them. This isn’t a jet engine rotor, it’s a spark plug. Even at six sigma levels, there will be escapes. You going to slow the entire line down to do 100% machine vision and full functional testing? Not going to happen.

The devil is in the details. It appears simple but you can bet there are quite a few critical aspects to making one. I can tell you from first hand experience, it doesn’t take much to screw up a glass (ceramic) to metal seal, as one example.

I never had a bad one but my BIL had an electrode come off after installation. Must have been an Autolite 'cause he’s a Ford guy. Kinda messed up his engine but they took care of it. I did have a parts guy tell me once that it “seemed” that the AC plugs sold at discount places didn’t seem to be the same quality as what the normal pro parts shops got. He didn’t have any proof and wasn’t trying to argue or anything, just made the comment that in his years of parts sales, seemed like they had more problems from the discounters.

I’ve never experience a bad new spark plug, but I’ve seen some weird stuff with new parts. I replaced a dome light with a bulb from the dealer 3 times and every one of those bulbs burned out within 3 months. The dealer shop must have had the bad luck to get a whole drawer full of bad dome light bulbs, as the next time I purchased the bulb at a different parts store, and that bulb was worked fine for 15 years. I had a similar problem with fuses one time. An entire 50 count box of 10 amp fuses were all bad. They were marked ok, as 10 amps, and had continuity by the DVM, but I measured the resistance and they all had 0.2 ohms resistance. That’s a 2 volt drop with 10 amps. No good for a 10 amp fuse.

Well I check the gap, but trying harder every day to buy stuff that is not made in china, and doubtful there is the quality control necessary in that country, even down to the basics, oops sorry there is lead in your toothpaste. Sure just tonight I replaced a pump in an amana washer 22 years old, 46 bucks, but given the garbage that is put out today a good investment in my book.

I have an engine code, I don’t remember the code. Cylinder number two is misfiring. I replaced the plug on that cylinder. It was an autolite copper plug, I used from Advance auto parts. Cylinder 2 is still misfiring and I have a suspicion that the plug might be bad out of the box. I am going to get a a.c delco platinum plug and see if the misfire goes away. I will post what happens after I replace the plug.

Did you replace the HV wire (assuming there is one)? that could be the problem.

Or, just swap plugs between #2 and another one and see if the error code follows or does not.

Re: bad components, my take on that (from experience in the semiconductor field) is that the auto manufacturers cannot afford the (at a guess) 1% failure rate off the production line. They would insist on a much lower rate, perhaps 0.01% and require the parts manufacturers to do testing to ensure that.

1% failure rate and every car off the line would have dozens of problems. Even 0.1% would result in many problems.

But consumers don’t have the clout to demand that type of testing, so we get them right off the production line. Although something that had lots of components, such as an electronic assembly, would probably have functional testing.

Bosch had a rash of defective plugs when they started bringing them from India over a decade ago. Come to think if it though, I have not seen a plug made in India for a long time. I’ve been using NGK and Denso since the 1970s and never seen a bad one.

You can get bad or incorrect parts of any sort, no matter how simple or how common. And it isn’t all that uncommon. It’s always wise to check parts out of the box to see that they’re correct and appear in good working order. Comparing them with the old parts when possible is also prudent.

I got bad (incorrect) shocks out of the box from Sears once. Brought them back. They gave me different ones. They were wrong too. Brought those back and got new shocks at VIP. They were perfect.

I once got a header pipe delivered for my old pickup… without the bunghole for the upstream O2 sensor!

It’s always prudent to double check what came in the box.

So I was at the boat guy, bought some new plugs no box, dropped one and bent the anode, had to re gap it, but I have never had a bad plug when bought new, time to look elsewhere for trouble I think.

Many plugs are bad out of the box for various reasons. Cracked ceramic is the greatest problem I have run across but there was a production run of Champion plugs with too much internal gap that caused some problems. And on several occasions I recall both Ford and GM changing the specified plugs for various engines to eliminate various driveability problems and eliminating the old number but in doing so parts stores shelves still had the old number often in several brands with books that specified them as the correct part. Cold starting an Oldsmobile with spark plugs gapped at .085" could be difficult but long ago the factory specified such a plug until they had enough complaints.