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What Was Your Spark Plug Gap?

136703 Views 474 Replies 193 Participants Last post by  snowwy66
If you changed your spark plug gap per this thread or this thread, please report what the original values were here. If you have yet to change them, please remember to report the original values.

My case with GM has been escalated to a district case manager at GM to hopefully get some exposure on this issue. My primary goal is to allow people to go to their dealerships and have their spark plug gaps checked and corrected (as there has been a 100% error rate so far), and the more people and numbers I can present them with, the better.

If your username is on the below list, I already have your numbers down. If not, please post them. I need specific values, such as ".022, .023, .025, .025." I will also need the model year of your Cruze.

We have 37 cars recorded so far. I'd like to get at least 50. My current spreadsheet is also attached.

InsaneSpeed Steve
Red Dragon
Higgs Boson


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looking at your spreadsheet, seems we should also be recording model years also. My 2012 was .019,.024,.025,.024
Good suggestion.

If those who have already reported their numbers would provide the year of their vehicle, I can certainly have that added to the spreadsheet. I will add those values for all newly reported gaps.
It would be nice to know if the engines are 1.8 or 1.4T as well. This may give us an idea about the severity of the problem for each engine.
I have been making a mental note of this and have not yet noticed any trends.

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Spreadsheet updated.

I've decided I'm going to go through it later and get the years. Easier than having every person post in this thread.

41 cars have currently been reported in this spreadsheet.


Well you've convinced me to open her up and check.

Question: Where do you buy these spark plugs from? No online store carries them. Even the NGK website does not list 2011 Chevy Cruze as one of it's options.

I only ask in case I break the tip or something.
Any auto store should have them. I can't imagine why they wouldn't. Absolute worst case, a dealer will have it. You can also use a different brand Iridium plug.
For those of you who work better visually, I graphed Xtreme's sheet after adding albow77. There is a very definite peak at 0.025 with the plug gap margin of error being -0.002 +0.001.

View attachment 5841
That visual graph sure makes it look like NGK thought they were supposed to be .025, and there were serious quality control problems on top of that.
I would go with the 0.035" what's in the GM maintainence manual. It's more current than the owners manual.
I'm not sure why some people still insist on using the owner's manual or what logic there is in assuming it is a more reliable authority than GM Global Connect, the GM service manual available to all dealerships, and AllData. The owner's manual was probably never updated since the production of the Cruze started. I'm fairly certain the same cannot be said of the service manuals.
Thank you to everyone who has provided their numbers. I've recorded everyone's results in my spreadsheet, which now has 49 vehicles and 196 plugs recorded.

If looking at this spreadsheet, please note the orange highlighted values. These represent owners who provided an approximation, such as "all 4 were around .025." I believe that, for statistical reasons such as the graph provided on page two, it is important to include those.

The updated spreadsheet is attached.


did my gaps last night and i found from right to left .019 .023 .021 .023
2012 M/T 1LT
Wow. Those are all much lower than the average, and the 2nd person who has reported a .019 gap. How's it run now?
Just updated the spreadsheet with the newest information. 57 cars have now been reported.


Uploaded a new spreadsheet with the latest numbers. I changed the formatting a bit to make it easier to read, and added a smooth chart.


Could you add a vehicle manufacture date to this as well (assuming it has been provided)? Since all my plugs were the same, I'm curious if the issue has been somewhat looked at recently. Not saying they're set "right" but, at least they were all the same.
I've seen many with a 2011 and a 2012 that also had the same consistency. I haven't noticed any correlation there.

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how are you gapping iridium plugs took me 1 hour withpro feeler guage.
I also took great care to not destroy iridium tip . these are the hardest alloy spark plugs I have ever checked.
0.028 is the dwell I have .
I used the following tool set, which includes a tool (the one pointing downward) with which you can easily adjust the electrode without touching the tip. $7 at your local auto store.

What was .028? Your original gap, or the gap you adjusted to?
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Well i checked mine today and there gap was all .019 so i regapped them all to .035 and i have a 2011eco mt
Wait, so you're saying all 4 of them were at .019??? I can't begin to imagine how horribly your car ran before you adjusted them.
What is happening here?? There is so much variation in the gaps here ... But it seems like theat Most of them are WAY too small
Why do you think I made such a big deal out of this? Between the 3 threads I created, there are 25,000 views.

Like maybe running to cool or just saying it is too cool? :iagree: with wallbngr's previous post, there is a lot of variation between the gaps. but how can it be when they are all from the same company and all machine built? :uhh:

Oh yea and I also forgot to say that all but one plug was barely hand tight and none of the crush washers (except for one) was crushed...seems a little shady to me :$#angry: :wtf:
Shady would be generous, lol. Not only is the consistency terrible, but based on the averages, we can come to a conclusion as to what *someone* thought they should have been, which points blatantly to .025". However, the only place that .025 is within spec is the document from the EPA for emissions testing where they noted the Cruze 1.4T motor's spark plug gap spec is .0236-.0276. No other document from GM or elsewhere indicates that this is anywhere close to correct.

With gman's spec, we have 70 cars reported. I'll post the spreadsheet again on Monday. That said, I highly encourage everyone who will do this to continue to report their spark plug gaps. Perhaps we can start seeing a trend if GM were to finally take note of this error and make some corrections. It wouldn't surprise me if all of a sudden, people started reporting higher gaps when checking their plugs.
Well I just hope that something is going to happen's not that it is hard to do, but it's the fact that it should have been done from the factory...has anyone talked to our GM Rep about this yet?

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In my case, 4 GM reps, one district case manager, and Stacy on this board, who came back saying that some "subject expert" told her in an internal email that the owner's manual is CORRECT and the service manual is WRONG. I capitalized those words because she did as well in her quote of that email. Supposedly GM Powertrain is working on "fixing" the service manual. Really? This is after the district case manager I worked with insisted that I should consult with my dealership for clarification if in doubt.

I question if that "subject expert" is from a legal or risk management department. Per the other large thread regarding this topic, I sent an email to a contact over in GM Powertrain on Friday night. I'm waiting for a reply on that since customer service is hesitant to offer any useful information.

Here's my message to anyone from GM that may be reading this thread. You have a finite amount of time left before I contact my local media regarding this issue as I'm running out of options. That time will expire when I have recorded 100 people in my spreadsheet. We are now at ~70 within a month's time. I figure 100 owners and 400 spark plugs with a very broad demographic should be plenty (as if the data isn't conclusive enough already), and you (GM) have had long enough to respond responsibly.
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...with no disrespect toward Stacy whatsoever, but maybe GM should be consulting a "...SPARK PLUG (GM-Powertrain) expert.." rather than a "...SUBJECT expert..." (which IMHO is merely PR-speak for "dummy")?
I asked her for the name or at least title of this "subject expert" in my first response and she didn't respond to that question. I asked her again in my second response. I wonder if she'll come back with anything.

I'm simply not buying it. This feels like dirt swept under the rug.
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I'll give it till Wednesday to let that guy from GM Powertrain respond before I give up dealing with GM directly.

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I'm getting the run-around from Tom Read at GM. He's avoiding all of my questions and blaming all of the variance we've measured on user error. I will be posting his reply as soon as I can determine where to do so.
So he's basically saying that 100+ people are idiots and can't read 400+ spark plugs on a gauge?

Yeah, I'm sure it's user error...
Precisely. I became a bit irritated to say the least. Sounds like I'm talking to a lawyer, not a GM Powertrain representative.
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