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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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My question (and really everyone's should be) is are the plugs gapped wrong or is GMs listed spec wrong?
Hey, i regapped mine this morning. N noticed something awesome. The ride is smoother, more responsive. And for thise who have a auto and use the manual part, notice when ur stopping after 3rd gear the car knocks by dropping from whatever gear to 1st just to stop the car???....well mine does and after regapping just a lil i noticed the knock was almost gone. Its a lot less now. Im regapping again to remove all knocks and ill report back. And extreme, good job on the find. U may not want to take full credit but aleast take the credit for letting others know about something so stupid like this. My plugs where almost touching eachother. I used a ruler to measure the point to bend n saw it was 2mm away from it. Like fml!!! Im gonna respace to about .28 or if i can .30and then ill let u know tomorrow on a differnace on the knocking n so on.
For the love of god please don't use a ruler to gap your plugs. Use a proper tool.
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