how much spark plug gap difference is close enough?

A

apollo18

Joined
May 27, 2023
Messages
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hey all bought new ngk 7751 for my 14 rdx from rockauto and i also bought that wire style type of gap tool. i was debating between the feeler gauge one and the wire style but decided with the wire

sadly my wire gap tool's closest gap setting is 0.044 and it seems that these plugs come pregapped at 0.043 (differing info but seems that ngk site says 0.043)

as far as i know my vehicle doesnt easily tell us the gap size, manual seems blank about this, some people say its supposed to be 0.044 but some say 0.043, i think could also be due to issues with what it is actually pregapped from factory as and the misinformation regarding that. i could be wrong but if ngk says this plug comes at 0.043 and seems to be the case, i just don't see why acura would want us to further the gap from a factory plug unless im wrong

so at the moment, i eyeballed all my plugs with my tool and as long as they slightly engage the wire tool surface i call it close enough to 0.043 since the gap would have to be 0.044 on my plugs to easily pass thru the gap tool. i know i could just gap them all to 0.044 with my tool but since they already came at around 0.043 i thought it would be easier just to keep it at that

so my question is if my plugs are ranging between 0.042 - 0.043 ish of gap is that fine? or should there not be that much variance between each other?

the reason i can't set properly is cuz my tool's closest setting is 0.044 so rn im eyeballing what i think 0.043 would be

thanks!
 
worn spark plug gaps are stupid wide when they need to be replaced There is no maintanance interval where the spark plugs are removed and regapped every 20Kmiles or so. They just let them go until you start getting poor gas mileage or they get fouled due to another issue (Valve/piston ring leak, rich burn, etc)

No need to overthink it. Its OK to start on the low side and let it open up as it wears.
 
I'd worry more about knocking off a fine metal "cap" (if applicable) than about a .001 inch difference.

Of note, the listed gap is a service replacement. Optimum is wider. By how much? Who knows.

It's good to verify pre-gapped plugs in case they were roughly handled on the way to your garage. But I wouldn't even try to regap them if they were within a few thou of spec.

Seems like a good time to buy a new tool, one of those cheezy "ramp up" feelers the size of a 50 cent piece. Don't be jamming things like your current wire tool.
 
eljefino said:
I'd worry more about knocking off a fine metal "cap" (if applicable) than about a .001 inch difference.

Of note, the listed gap is a service replacement. Optimum is wider. By how much? Who knows.

It's good to verify pre-gapped plugs in case they were roughly handled on the way to your garage. But I wouldn't even try to regap them if they were within a few thou of spec.

Seems like a good time to buy a new tool, one of those cheezy "ramp up" feelers the size of a 50 cent piece. Don't be jamming things like your current wire tool.
Click to expand...


Ty sorry I don’t recognize that word fine metal cap

Is it somewhere on the tip?
 
If you have a precious metal plug (platinum, iridium, ruthenium) they sometimes "stick" the precious metal to something less precious underneath. If you knock it off, the softer metal will still make a spark but wear out much faster.

And you've got a little hard thing bouncing around that can bust your piston top or valves.
 
eljefino said:
Of note, the listed gap is a service replacement. Optimum is wider. By how much? Who knows.
Click to expand...
elj,

Why is wider more optimum? I thought wider requires more current and is harder on the coils?

I agree with your statement that one has to be OCD careful with the fine metal electrodes when gapping them, but I hate those coin type feeler gauges for some unknown bias and use wire type feeler gauges very gently.
 
A wider gap stands a greater change of igniting an air fuel mixture. Way too wide will hurt your coils. But when the manufacturer tells you to gap a copper plug to, say, 0.040" then ignore it for 30k miles, they know the gap is going to grow and the car's going to run fine the whole time.

In the old days of points ignition they wanted some small gaps, like 0.028". It's advised to open things up if you improve your spark such as with an aftermarket HEI distributor. Coil-on-plug is great because each coil fires less often and has more time to recharge, to jump larger gaps more surely.

As emissions laws get stricter and ignition parts got better, tolerance for misfires has gone way down.
 
doitmyself said:
elj,

Why is wider more optimum? I thought wider requires more current and is harder on the coils?

I agree with your statement that one has to be OCD careful with the fine metal electrodes when gapping them, but I hate those coin type feeler gauges for some unknown bias and use wire type feeler gauges very gently.
Click to expand...
I don't think wider is a way to start off for a Pass car where you are expecting long service. It will erode and open across hours in service.

I only gap check Ir with a MM or a grate reticle - no touch!

I am sure the wire type gap gage is easily within 2 tenths of a mil (when not worn out of spec) It is the process of measurement that has variability. You could just verify this simple tool with a mic.

Good enough as this is just a casual use - not process control or tool making.

I had metrologist in my skill set when I was a young(er) buck.

But ... can't see well and pretty dang deaf these days - Arco
 
Last edited:
ty all i did kinda play with the gap but i don't think i damaged anything as all the plugs look the same and i didn't touch the electrode or the inner part of the iridium tip

should be fine i assume
 
doitmyself said:
Why is wider more optimum? I thought wider requires more current and is harder on the coils?
Click to expand...
It does require more current, but it also creates a more powerful spark, and initiates the burn a bit faster. This has a similar effect to advancing the ignition timing. It results in more power and higher efficiency, at the expense of increased risk of detonation.

Since emissions and fuel economy tests are done with newer spark plugs, I'd imagine that the specified gaps are going to be pretty much optimal, unless you're using higher octane fuel.
 
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