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Are Your Spark Plugs Gapped Incorrectly?

152673 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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Thanks X, i seen the the other thread before, I will be checking both cars.
You have a link to were it calls for .33-.37 gap on 1.4L motor?

Sent from my DROID X2
Both of my cruzes were at .024
They are now at .035

Sent from my DROID X2
Has anyone tried dropping back to a lower octane level after regapping? If detonation is causing performance issues at say 87, opening the plug gap up may remedy that issue - or make it worse depending on the source of ping..just thinking it may provide some cost savings and possibly even better performance. Just a thought.

Just my .02 here.

I ran 87 octane for the 1st 2000 miles, never heard or felt any ping or knock in the engine. X recommended me to try 91 octane non OXY fuel ($.46 more per gal Here), so i did, two takes and 850 miles. I also think the engine is breaking in but i got 40.4 mpg on way to and from work. I regapped the plugs, and swapped back to 10% ethanol and 87 octane and my DIC it still showing the same MPG as my last two tanks with 91 octane.

Here is a pic at 265 mile into the tank. 87 octane with 10% ethanol.

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