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Are Your Spark Plugs Gapped Incorrectly?

152671 Views 545 Replies 129 Participants Last post by  wasney
I'm creating this thread to increase exposure of what appears to be a very common issue (affecting 100% of Cruzes so far). This stemmed from the following thread:

My original experiment was to increase spark plug gap over what they are gapped from the factory and test for measurable gains in fuel economy. What I didn't realize was that I had actually gapped them to the correct spec, and they were gapped much too small from the factory.

AllData specifies a spark plug gap of .033-.037 for the 1.4L Turbo motor. Reports so far have come back with .024, .025, .026, and .029 as measured spark plug gaps from the factory iridium plugs. These should have been pre-gapped from the distributor, but clearly weren't.

Coinneach checked his spark plug gap on his Cruze LS with the 1.8L N/A motor and found a .020 spark plug gap, which is absurd for a N/A motor and is smaller than he or I have ever seen before in any engine. He increased that to .035 and had the following to say when I asked if he noticed a difference:

Like a whole new beast. It's not quite as zippy as the 1.4T in the Eco that I drove when I was shopping, but it's a *censored* of a lot snappier now.

I currently don't know what AllData specifies for the Cruze LS, but if someone can get that information into this thread, it would be of great benefit to everyone. Hopefully, someone will get a tutorial/video made soon. There are significant performance and fuel economy gains to be had by correcting the spark plug gaps on these cars.
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ok just got doing this to my cruze with the 1.4l turbo... man glade i did... one was gaped at not even .19 and the others not even close to .25... gaped them all at about .36... went and fuelled up.. will report back later in the week what my mpg are.. i've been getting about 25 to 27 mpg on a full tank....again glad i did this.. thanks for the heads up
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.19!!! Wow. It's disturbing to find that these are gapped so far off what they should be, and so inconsistently at that!

Did you notice any difference in how the car drove?
seemed a bit peppier.. didn't really have to drive to far for gas.. so i will pay attention tomorrow on the way to work.. and yes it was quite a difference in the gap... plus all the springs were wedged off to the side...
Springs were not wedged originally. When you unseated the coils from the plugs they do that FYI.
my bad.. first time doing anything with this car... only had it for about 3 weeks now
ok i'm reporting back on my regap... on a tank of 92 10%ethonal... i got 389 miles on my tank... and my mpg went up by 5.. so i'm going to say that regaping is a must and gets better mpg.. a big thank you goes out to whoever found this problem....
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I can't take all the credit, but I'm glad you saw a significant difference. What were your original gaps, and which engine do you have?

as my previous post i have the 1.4t and they were gaped at not even a .19 to .24
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