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Are Your Spark Plugs Gapped Incorrectly?

152666 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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You do this one step at a time, patiently and slowly. I believe it's the smaller of the common spark plug sockets to get it out. You'll also need a torx bit, but I don't remember what size it was. Don't adjust gap with one of those coin looking things; you'll need proper feeler gauges. You might otherwise damage the plug as it's an iridium tip. Once you get the engine cover off, the coil bar is right in the center with the two bolts that need removing, and you can wiggle it right out (again, patiently and slowly). Check inside the boots to make sure the springs didn't bind, and proceed to the spark plugs.
I've only just used a coin thing. What do you suggest we use for gapping them correctly..?
Please report back with what you find as far as the original gaps go.
How much does that cost

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Adjusting the gap, assuming you have the tools, costs nothing but maybe 15 minutes of your time. The gap tool shouldn't cost more than $3 or so at Pep Boys, Autozone, etc.
The cost of the tool is my question. Thats the tool linked above? Or just a coin gapper? It looks like itd be more than $3.

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I gapped mine today to .28. Mine were all below .25, I did not get exact measurements.
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Mine is a tuned 1.4L and this should be the correct GAP for a TUNED 1.4
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