Spark Plug Gap

[jchasp59]

I just checked my spark gaps a couple days ago as I have a rough idle/slight miss and symptoms that feel exactly like improperly gapped plugs. I found the factory gaps to be: .026, .025, .026, .027.
2,000 miles on the car now... no CEL (yet) but I'm beginning to suspect the ign. coil is already on its way out as Papasonic and a couple others had this issue. I may just shotgun the iridium autolite plugs and a new coil at it and see if that clears it up.

I have rough idle, as well, that the dealer unsurprisingly 'Cannot Duplicate'. Checked my plugs, all were gapped at 0.025. Googled, and then called the dealer and found that 0.025 is the "correct" gap. Beats me what's causing my rough idle and hiccups, but one thing is for certain, the dealership isn't interested in helping me at all! So many problems and little or no support from the dealership. This'll be my last GM product.

 

[sx sonic]

Are there any other dealers near you. Some dealership are very helpful and underatanding, other are horrible and make you want to pull your hair out (the place I bought my car from is one of them)

If there is another GM dealer nearby try them out, you have a new car and it Should not give you problems and if it does the dealer should do anything they can to make it right.

I hope you're able to get your issued resolved soon!!

-tyler

 

[Larry]

I have rough idle, as well, that the dealer unsurprisingly 'Cannot Duplicate'. Checked my plugs, all were gapped at 0.025. Googled, and then called the dealer and found that 0.025 is the "correct" gap. Beats me what's causing my rough idle and hiccups, but one thing is for certain, the dealership isn't interested in helping me at all! So many problems and little or no support from the dealership. This'll be my last GM product.

The "correct" gap is inside your owner's manual, as stated it is 0.028".

 

[Bogus]

I read about half of the first page of this thread (I am just way too impatient to read 3 pages) and it sounds like this is my problem.

I hardly make any power under 3500 RPM's. Literally, especially on hard accelerations from idle to around 3,250-3,500 my car is kind of bogged, but when the RPM's hit 3,500 it's like a small kick in the ass!

 

[Bogus]

The "correct" gap is inside your owner's manual, as stated it is 0.028".

Is this for both 1.4 & 1.8?

 

[Larry]

I read about half of the first page of this thread (I am just way too impatient to read 3 pages) and it sounds like this is my problem.

I hardly make any power under 3500 RPM's. Literally, especially on hard accelerations from idle to around 3,250-3,500 my car is kind of bogged, but when the RPM's hit 3,500 it's like a small kick in the ass!

This won't help with turbo threshold (mistaken for turbo lag), it only helps with rough idle and throttle response. Also hesitation at WOT, stuttering, misfires, etc.

 

[Larry]

Is this for both 1.4 & 1.8?

The 1.8L has the same gap in the owner's manual, but you might want to do some research. 0.028" seems tight for a N/A motor, I'd do 0.035".

 

[Bogus]

This won't help with turbo threshold (mistaken for turbo lag), it only helps with rough idle and throttle response. Also hesitation at WOT, stuttering, misfires, etc.

The 1.8L has the same gap in the owner's manual, but you might want to do some research. 0.028" seems tight for a N/A motor, I'd do 0.035".

I have the 1.8 not the turbo. I'll check my gaps when I get off work today. You really think I should set it over what the manual recommends?

Has anybody taken pictures of the process?

 

[Larry]

I have the 1.8 not the turbo. I'll check my gaps when I get off work today. You really think I should set it over what the manual recommends?

Has anybody taken pictures of the process?

I advise you to read the following threads and come to your own decision:

GMs Official Statement Regarding Spark Plug Gaps

Are Your Spark Plugs Gapped Incorrectly?

What Was Your Spark Plug Gap?

As for how to gap your plugs:

Correct way to check, set and adjust your spark plug gap.

 

[CoHPhasor]

I advise you to read the following threads and come to your own decision:

GMs Official Statement Regarding Spark Plug Gaps

According to this there is no way in hell I'd gap my plugs to .035".

Per GM's recommendation (after review with engineers):

"spark plug gap information was incorrectly listed as 0.85 - 0.95 mm."

.85mm = .033"
.95mm = .037"

"A change is being implemented to correct that information to 0.6 - 0.7 mm."
.6mm = .024"
.7mm = .028"

Now, as to which one to run and why 2 completely different motors use the exact same gapping, I couldn't tell you.
I definitely would choose to run closer to .028" on the turbo unless you were running higher boost though.
Say for example you're running the Trifects tune hitting 20psi - I'd probably try 26 and then work my way down if I had any problems.
(Just insurance against spark blowout.)

Running .038" is out out of bounds if you're rounding properly and by all the performance/mileage increases seen shows a lack of efficiency.
It's honestly pretty crazy for there to be that much difference between the original printed spec and the actual optimal gapping. (A whole hundredth)

 

[Eric Smit]

I checked my plugs this weekend. It was .030 across the board, except for one .034. I gapped them all to .028 and feel no difference.


-Eric Smit

 

[Bogus]

I checked my plugs this weekend. It was .030 across the board, except for one .034. I gapped them all to .028 and feel no difference.


-Eric Smit

lemon!

 

[Larry]

According to this there is no way in hell I'd gap my plugs to .035".

Per GM's recommendation (after review with engineers):

"spark plug gap information was incorrectly listed as 0.85 - 0.95 mm."
.85mm = .033"
.95mm = .037"

"A change is being implemented to correct that information to 0.6 - 0.7 mm."
.6mm = .024"
.7mm = .028"

Now, as to which one to run and why 2 completely different motors use the exact same gapping, I couldn't tell you.
I definitely would choose to run closer to .028" on the turbo unless you were running higher boost though.
Say for example you're running the Trifects tune hitting 20psi - I'd probably try 26 and then work my way down if I had any problems.
(Just insurance against spark blowout.)

Running .038" is out out of bounds if you're rounding properly and by all the performance/mileage increases seen shows a lack of efficiency.
It's honestly pretty crazy for there to be that much difference between the original printed spec and the actual optimal gapping. (A whole hundredth)

That's why I told him to read it and come to his own conclusion. If I had a 1.8L, I'd gap it between 0.030-0.035". But that is my opinion and I won't try to pass it off as the best or correct way to do things.

 

[Eric Smit]

lemon!

-Eric Smit

 

[Bogus]

That's why I told him to read it and come to his own conclusion. If I had a 1.8L, I'd gap it between 0.030-0.035". But that is my opinion and I won't try to pass it off as the best or correct way to do things.

The engineer was very clear when he said to gap them both the same. But I'd be lying if I said I wasn't a little worried with my 1.8.

 

[Larry]

The engineer was very clear when he said to gap them both the same. But I'd be lying if I said I wasn't a little worried with my 1.8.

Originally the 1.8L gap specifications were different, later they changed it. It's all in the threads I linked, I read through about 200+ pages before the information started to repeat itself.

 

[CoHPhasor]

Originally the 1.8L gap specifications were different, later they changed it. It's all in the threads I linked, I read through about 200+ pages before the information started to repeat itself.

Normally I'd agree and say it's an opinion-based thing, but not if GM changed their service documentation in order to correct it as cars are worked on in the future.

 

[Bogus]

To play it safe I think I'll just set them to the max.

BTW what are ours made of? Should I bend these or buy new ones?

 

[lambertsonic]

I ended checking my plugs , they were all at a perfect 0.030 . Awesome !

 

[Bogus]

I ended checking my plugs , they were all at a perfect 0.030 . Awesome !

Ahhh my OCD is kicking in!!! GM says .028 MAX but other people are saying bigger. I know car manufacturers do things to limit a car's performance but I don't want to damage anything.