Spark Plug Change Oddity (1 Viewer)

[jnance50]

I changed my plugs today at 30k miles and found something odd. Every resource I’ve looked at, including the FSM, says the gap on the plugs should be 0.044. When checking my factory plugs, they were at 0.038. When checking the new plugs from the box, they were also at 0.038. According to the manufacturer (NGK) they should have been at 0.043. My first thought was that my gap tool must be wrong, but I also verified the measurement by feeler gauge and caliper, as I just couldn’t believe that both old and new would be the same and wrong. I set the new plugs to 0.043 and the engine is running fine, if not a a little smoother; haven’t driven enough to notice any fuel consumption changes.

Thoughts? Anyone experience anything similar?

 

[manofthewoods]

I changed my plugs today at 30k miles and found something odd. Every resource I’ve looked at, including the FSM, says the gap on the plugs should be 0.044. When checking my factory plugs, they were at 0.038. When checking the new plugs from the box, they were also at 0.038. According to the manufacturer (NGK) they should have been at 0.043. My first thought was that my gap tool must be wrong, but I also verified the measurement by feeler gauge and caliper, as I just couldn’t believe that both old and new would be the same and wrong. I set the new plugs to 0.043 and the engine is running fine, if not a a little smoother; haven’t driven enough to notice any fuel consumption changes.

Thoughts? Anyone experience anything similar?

A couple of bits of information (which might lead to questions, or perhaps your vehicle might be different??)...

My vehicle specifies new plugs at 120k miles. And, barring some catastrophic engine problems, I don't/won't see a need to change them early. That is because the gap will (slightly) increase over the miles. The gap increase may actually enhance combustion efficiency due to a slightly larger flame front. The coils that provide the spark are quite powerful and can easily handle a wide(er) gap. Basically, they don't wear out - much. And, if the intake systems, including a functional PCV are doing their job; the plugs shouldn't be carbon fouled. It's highly unlikely you'd "feel" any difference in a new sparkplug or a gap change - I'm afraid our butt dyno's lie to us ALL THE TIME.

Happy new year

 

[jnance50]

A couple of bits of information (which might lead to questions, or perhaps your vehicle might be different??)...

My vehicle specifies new plugs at 120k miles. And, barring some catastrophic engine problems, I don't/won't see a need to change them early. That is because the gap will (slightly) increase over the miles. The gap increase may actually enhance combustion efficiency due to a slightly larger flame front. The coils that provide the spark are quite powerful and can easily handle a wide(er) gap. Basically, they don't wear out - much. And, if the intake systems, including a functional PCV are doing their job; the plugs shouldn't be carbon fouled. It's highly unlikely you'd "feel" any difference in a new sparkplug or a gap change - I'm afraid our butt dyno's lie to us ALL THE TIME.

Happy new year

Happy new year! Yeah, this was on my “baselining” list for the last 2 years because it didn’t feel urgent. The gas mileage of my 200 (2021) was low even by LC standards, even when stock, averaging around 13.5mpg.

Lately, I’d noticed when under load going up into the mountains that I’d sometimes get what felt like a misfire when under heavy load. Not consistently reproducible, no codes, and not a harsh misfire, subtle, almost like partially incomplete combustion. That’s what’s triggered me to change them. This is what I meant by “smoother” and seems to have gone away, but time will tell.

That being said, I still don’t understand why my factory plugs AND the new plugs would both be gapped at 0.006 less than specified by the FSM.

FWIW, none of the old plugs looked terrible.

 

[bloc]

What year 200?

On my 2013 the original plugs were Denso SK20HR11 and from my notes the replacements did gap correctly at .043

 

[jnance50]

What year 200?

On my 2013 the original plugs were Denso SK20HR11 and from my notes the replacements did gap correctly at .043

2021 and .043/.044 is what I was expecting.

 

[Artie]

Lately, I’d noticed when under load going up into the mountains that I’d sometimes get what felt like a misfire when under heavy load. Not consistently reproducible, no codes, and not a harsh misfire, subtle, almost like partially incomplete combustion. That’s what’s triggered me to change them. This is what I meant by “smoother” and seems to have gone away, but time will tell.

I had a similar experience on my ‘21 a couple years back, even brought it up on here looking for advice since we are new to the platform….it went away after a while. All I can guess is it was due to some bad gas at a somewhat sketchy gas station while we were on a big road trip. It was enough that even my wife noticed it. We were towing and at altitude.

You have one kinda wet plug in that picture but not something I’d obsess over.

 

[linuxgod]

I had a similar experience on my ‘21 a couple years back, even brought it up on here looking for advice since we are new to the platform….it went away after a while. All I can guess is it was due to some bad gas at a somewhat sketchy gas station while we were on a big road trip. It was enough that even my wife noticed it. We were towing and at altitude.

You have one kinda wet plug in that picture but not something I’d obsess over.

Ive gotten that feeling when towing in 95F+ heat through Nebraska or Texas. Switching to premium fuel helped once I discovered the engine was backing off timing too much. KCLV would drop to around 10.5 from the normal 14-15 range. Premium adds a few degrees of spark advance and KCLV sits around 18-19 normally with it backing off to 13-14 which runs fine.

 

[Artie]

Ive gotten that feeling when towing in 95F+ heat through Nebraska or Texas. Switching to premium fuel helped once I discovered the engine was backing off timing too much. KCLV would drop to around 10.5 from the normal 14-15 range. Premium adds a few degrees of spark advance and KCLV sits around 18-19 normally with it backing off to 13-14 which runs fine.

I think this is what you told me in response to my inquiry that day.

 

[AZBoatHauler]

Is the one is the brown insulator missing the iridium tip?