spark plug gapping...

[T2urtle]

Just pulled the plugs off the GF's 03 lancer at 67k. Last time i did the plugs were at 40k and i installed NGK copper plugs that should be good for 20-30k. I know when i put those copper plugs in they were gapped at specs of .035

When i pulled the plugs today, i found they were at .070+, kinda shocked. One was covered in oil ( need to replace spark plug tube seal when i do the valve cover gasket). I kinda found that weird. And then i remember she did have some issues upon starting in cold weather.

I know the larger the gap the more the spark has to work. But really its a 2.0 NA engine, not a higher performance so gapping isn't super important. I think i MIGHT of stumbled upon the "struggling to start up every morning issue" i had a while back. And the one time it took 2 tires to fire up, do you guys think its spark plug gapping related?

I put in new NGK plats thanks to advance auto's coupon. And gapped them at OEM specs of .035

 

[StageLeft]

I've only done plugs on two cars, both I used the OEM platinum 100k plugs and in both cases they were gapped to spec from the factory. I use OEM because when I'm at autozone and they have these four pronged plugs that are supposed to be better than OEM my bullsh*t meter goes absolutely haywire and it just doesn't sit well with me.

 

[LTC8K6]

Well, they normally open up over time but that does seem like a lot.

 

[Pacfanweb]

You used copper plugs in a newer car? Did it have coppers to begin with?

I don't think coppers are designed to last long with today's ignitions. It takes a bit more "ass" to fire platinums or irridiums or whatever new cars specify, but current ignitions have it.
I would think they'd be hard on a copper plug, though...but I will confess that I don't know anything about your specific ignition specs.


As far as "working" the spark more.....increasing gap WILL increase the voltage. That's a fact, no way around that.

Now, this is a GOOD thing, since a small increase will give you a hotter spark.
You can increase gap too much, and that will still increase voltage, but it'll kill the amperage.

BUT....there is a nice "sweet spot" in later model ignitions (really, since the early 90's) where the coils can easily continue to provide the necessary amperage and even can increase it, when the gap is a lot wider, like .020" or so. They are essentially "over built" for their purpose.

I'll give you an example: I have a 99 Tahoe 5.7, and a 2004 Suburban 5.3. Tahoe has right at 150k on it, Sub had just over 120k. Neither have ever had the plugs replaced. Still running fine, still getting the same mileage they got with half the mileage, which was better than they got with low mileage.

I'm going to tune the Tahoe soon, and am very interested to see just how big those plug gaps are by now.

I remember (and I've told this here before but it's been a few years) when I worked at a Ford dealer for years, back in the early 90's....when Ford started using platinum plugs and upped their tuneup interval to 60k from 30k. We'd replace the plugs at 60k or so, and of course the gap would be way over stock....stock was around .046-.052" (coppers used .042-.046) and at 60k they'd be .070" and even more sometimes.
Well, you know at that gap the ignition is providing a nice, fat spark, with a good bit more voltage than at the beginning gap.

So, when we started getting these things in at 60k and replacing plugs with gaps at the factory spec, people started coming back in, complaining their gas mileage had decreased after the tuneup. We had tons of these complaints, and Ford was getting them all over, too......finally there was a service message or some other bulletin issued (don't think there was an official TSB) that informed us it was likely because of the reduced gap. The spark wasn't as strong.

 

[jlee]

.70??? Damn...people run tight gaps on MR2's (0.28), but that seems like a LOT.

I also burn through copper plugs in 5000-6000 miles...I'd run whatever OEM iridiums her car likely came with.

 

[T2urtle]

its a 2003 lancer auto not the evo with 67k now. pulled oem plugs at 40k installed coppers.

she told me it starts better now, i want to rule out the fact of the placebo effect, she knew i did the plugs and air filter and the car had a little struggle starting. i'll do the plugs again if we still have it at 100k

 

[LTC8K6]

.70??? Damn...people run tight gaps on MR2's (0.28), but that seems like a LOT.

I also burn through copper plugs in 5000-6000 miles...I'd run whatever OEM iridiums her car likely came with.

I think that's .07 and .028 ...

 

[jlee]

I think that's .07 and .028 ...

Yeah, that.

 

[DietDrThunder]

Copper vs. Platinum

Using an electrode material that is a more efficient conductor (like copper) than the platinum material, you can decrease the amount of voltage required to "jump the gap". The only problem with using platinum plugs is that they will produce a less powerful spark than a standard copper plug will at the same gap. This means that, as long as your ignition system can provide enough voltage to jump the gap on the spark plug all of the time, with platinum plugs installed in your car, your engine will produce less power than it will with copper spark plugs. The only way you can regain the power lost with platinum plugs is to open their gap out farther (a wider gap requires more voltage to jump the gap). Platinum should be gapped at 0.039in to 0.044in and Copper at 0.031in to 0.035in. In this case, the platinums will produce roughly the same spark energy as the copper plugs while providing an extended service interval (50K to 60K miles for platinums versus 20K to 30K miles for copper). It's just a question of spending $1 to $2 per plug (for copper) and replacing every 20K to 30K miles or spending $3 and up per plug (for platinums) and replacing every 50K to 60K miles.

Iridium vs Platinum

In my opinion, for a standard engined car, iridium isn't worth the extra expense ($13 to $18 per plug). Iridiums are more heat resistant, but unless you have a turbo charged engine and are always putting your foot to the floor, I can't see what advantage the iridiums have other than extending the service life to around 80K to 100K miles.


What do I run? Both of my newer vehicles still have the original OEM spark plugs, and neither have enough miles on them to warrant changing them. On my '63, with it having dual carbs and not fuel injected, the only way I can go is copper (the carbs don't have as good of control of the air/fuel mixture so it needs the hottest spark possible). I've installed a high voltage electronic ignition and I have the gap set to 0.045 in.

 

[Demon-Xanth]

I've seen plugs there were concave by the time they were swapped. Some engines don't seem to like platinum plugs though, so YMMV

 

[BW86]

You used copper plugs for 30k miles? wow, I change my copper plugs every ~10k miles

 

[Demon-Xanth]

You used copper plugs for 30k miles? wow, I change my copper plugs every ~10k miles

30k is a good mileage for mine to be swapped, 40k is pushing it.

 

[T2urtle]

You used copper plugs for 30k miles? wow, I change my copper plugs every ~10k miles

the hell...

i've always kept coppers at 30k, plats at 60k and if i ever go for crazy fancy plugs like iridium i would expect 100k for them. prices have came down on simple platinum plugs to like $0.50~$1 more then coppers lately so i'm going to forget about coppers.

I dont know where i got the numbers from, i didn't make them up. I read them somewhere. Plus all the manufactures want you do to plugs at 60k~ lifetime now anyways.

 

[LTC8K6]

It's 30K for the copper plugs in the Hemi.

I always wondered why they didn't use platinums and now I know. Copper is better for the application.

 

[WackyDan]

I get 30k out of my copper plugs and they do show signs of wear at that mileage... and I get worse mileage with those old plugs than with the new of course.

The computer should be able to adjust and map to the gap differences over time. My truck runs like crap after a plug change until I take her a mile or so down the road and back while the computer remaps to the new plugs....Same thing for O2 sensors.

On my bike, I use copper as well, they are $1.74 each and I change them every 5k or so as of late...as the bike likes to eat them... So I just change them every other oil change.