replacing all spark plugs?

F

flinter

Joined
Jan 7, 2003
Messages
631
Location
New Jersey
Hi,

When one spark plug is diagnosed to be bad and replaced, is it a good idea to replace ALL the plugs?

I ask this because my 2017 Hyundai Elantra SE 2.0, with just 40,000 miles, started misfiring and gave out a code "P0301- cylinder 1 misfired detected". The dealer replaced the ignition coil (covered still under Hyundai's 5YR/60K warranty) and the spark plug. But they just replaced the one plug in cylinder 1 and I was wondering if all 4 plugs really should have been replaced all at the same time?? This service solved the problem and the engine is running normal again.

Thoughts?

Thanks
Michael in NJ
 
I guess it really wouldn't matter that only one plug was changed. I always do the complete set then I don't have to worry about plugs for another 100K miles. If the plug service interval is 100K miles like on lots of cars you could just leave it as is and when you get to 100K change all 4. At that time 3 of them would have 100K and the one that was replaced would be at 60K. If the interval is anywhere around 40K just go ahead and replace them all now.
 
I would do all 4 of they are easy to get to. A friend has been taking hos 04 dodge truck to the local Firestone for maintenance since it was new.

It threw a code and was a missfire for the dr rear cylinder( forget which # that is). These 2 plugs are difficult to get to.

I pulled 14 bosch platinums and 2 completley worn out champions out of his engine. I am confident that the 2 champions were OE plugs
 
You probably don't have to sicne they're less than halfway worn anyway The bad coil probably destroyed the spark plug, thus shortening its life drastically. Since the other coils are fine, there is no need to replace the other plugs until 100k.
 
flinter said:
Hi,

When one spark plug is diagnosed to be bad and replaced, is it a good idea to replace ALL the plugs?

I ask this because my 2017 Hyundai Elantra SE 2.0, with just 40,000 miles, started misfiring and gave out a code "P0301- cylinder 1 misfired detected". The dealer replaced the ignition coil (covered still under Hyundai's 5YR/60K warranty) and the spark plug. But they just replaced the one plug in cylinder 1 and I was wondering if all 4 plugs really should have been replaced all at the same time?? This service solved the problem and the engine is running normal again.

Thoughts?

Thanks
Michael in NJ
Click to expand...
Widened plug gaps make the coil work harder and contibute to coil failure.
 
If those have the typical "100,000" mile suggested interval, I would leave them in until that point. No need to replace something that isn't bad OR that isn't at a recommended service interval yet. On a quick search, it looks like those cars are known for coil failures...
 
One spark plug going bad was just a fluke. This happens sometimes.
I'd leave the other 3 plugs alone and replace all 4 of them at 100K-105K like the OM calls for. Otherwise, you'll have one spark plug leftover from the 4 pk if you replace them yourself.

JMO,
CB
 
The code was specific to cylinder 1 and it sounds like the dealer fixed it up right. I would stick to the regular maintenance schedule going forward. None of the other cylinders had an issue so just leave them alone. The only downside: you'll eventually replace one spark plug before it's time.
 
flinter said:
Hi,

When one spark plug is diagnosed to be bad and replaced, is it a good idea to replace ALL the plugs?

I ask this because my 2017 Hyundai Elantra SE 2.0, with just 40,000 miles, started misfiring and gave out a code "P0301- cylinder 1 misfired detected". The dealer replaced the ignition coil (covered still under Hyundai's 5YR/60K warranty) and the spark plug. But they just replaced the one plug in cylinder 1 and I was wondering if all 4 plugs really should have been replaced all at the same time?? This service solved the problem and the engine is running normal again.

Thoughts?

Thanks
Michael in NJ
Click to expand...


I had a similar event with a 2000 Dodge Neon with only 32,000 miles on it at the time... Started missing really bad with a very, very quick on set... I went and got 4 Bosch platinum spark plugs and replaced all 4... Took 15 minutes tops. Car ran perfect after that.
Must have been some welfare plugs from the factory....

In this case like yours... Just me but I'd replace the other 3 too.
 
flinter said:
Owner manual says to replace at 105K.
Click to expand...
SO that is what I would do and not think about it any further. Dealer fixed cylinder 1 issue with coil new coil and plug. Either one could have been defective.
No reason what so ever to change the other 3 spark plugs, just like you wouldn't replace the other three coils.
 
I wouldn't trust the other 3 plugs.... And if it's a simple 4 cylinder motor... Takes what ?? 10 minutes to change them... And the plugs are say $8 a piece.... I'd do it.

Plugs can be no good from the factory.
 
The real question is, "why did they replace the plug"? Did the gap widen? Was the plug bad from the start? As far as the other 3, don't fix what is not broken, then do all 4 at 105K.
 
On a 6 cylinder motor that's like mine... Where it is not very easy to do... Ok maybe don't mess with them.

On a easy 4 cylinder motor that it is done in ten minutes ? That is a situation where it can be done. Easily. And I would bet that a bad plug caused that issue and it is possible the other plugs could be defective too. Just like my 2000 Dodge Neon.
 
This was probably a case of the coil going bad. It could have been a defective coil. A bad plug can also make the coil go bad. The plug not firing correctly will get fowled anyway. So best to put in a new plug. I would have preferred to have all 4 changed, but it is not necessary.



Rod
 
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