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2004 chevy trailblazer_ls
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38 Posts
Discussion Starter · #1 ·
I purchased NGK Iridium IX plugs from my local auto parts store the other day and I felt brave enough last night to give them a try. I have the I6 and all went well. The plug all the way in the back was a little PITA but not too bad. My only problem was the parts guy gave me a box of four plugs and two loose plugs. I installed the two loose plugs and when I opened the box of four, there were only three. Jumped on my bike and ran back up to the store and the clerk (a different guy) gave me a plug. Truck starts and runs and everything. The old plugs actually still looked good but since I just clicked over 90K miles, I did not want to wait much longer. I have been very happy with how smooth this engines runs. Mine runs great.
I was also reading some other threads on gaping plugs. Some say to gap them to OEM specs, others say they are gapped from the plug manufacturer. I checked the NGK website under their FAQ section and they recommend to gap the plugs to OEM specs. These plugs, according to their website, are gapped at .052 where the OEM spec is .042. They also advise when gapping to be very careful of the wire coming up the plug, mine is iridium. If that is damaged, it will screw up the plug. My plugs needed little adjustment as they seemed to be around .045-.050, according to my gap tool.
 

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2004 chevy trailblazer_ls
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262 Posts
Good to know, I will be changing my plugs soon as I am over 80k. I check the gaps every time because even from the warehouse they are sometimes off.
Yeah I just changed mine about a month ago and I just went and bought AC Delco oem iridium plugs. Mine were all pretty much gapped close OEM but a few of them needed tweaked
 

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2007 gmc
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159 Posts
Just changed out the plugs on an envoy a few weeks ago with the NGKs. Checked all and they were gapped to the OEM specs. Actually pulled them out again and rechecked all because I was getting a misfire code. Ends up the front plug did not seat correctly. Owner loves the NGK plugs and the increased mpgs.
 

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2002 chevy trailblazer_ltz
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2,762 Posts
Always check the gap,only takes a sec. but longer if you need to pull them out to do it.Like the old saying.There's never enought time to do them right,but always time to do it again.
 

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2007 gmc
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159 Posts
What was your MPG improvement?
Hard to pinpoint to just the plugs but I cleaned the throttle body then power foamed it, new air filter, engine flush, switched to synthetic oil and fuel system cleaner in the tank. She was claiming she was getting very close to 3 more MPG than her norm.
 

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2007 gmc
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159 Posts
What is the part # for the NGK iridium plugs for the I6
Fill out your profile because I could not look it up for you. In the 2005 GMC ENVOY 4.2L 6-cyl Engine Code I changed a few months ago the spark plug number was NGK4344.

You can look up the spark plug you need your vehicle yourself with the AMSoil Vehicle Application Guide
 
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