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2003 chevy trailblazer_lt_ext
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15 Posts
Discussion Starter · #1 ·
at how many kms is it reccomended to replace the sparkplugs in a 4.2 trailblazer
 

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2002 gmc envoy_sle
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1,380 Posts
well it's supposed to be 100,000 miles, so I think that works out to 160,000 KM. Just make sure you don't buy Bosch!
 

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2003 chevy trailblazer_lt_ext
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771 Posts
NGK Iridium IX

Stock No 4344
Plug Gap 0.050
LTR5IX-11
This is what I used 2 weeks ago, do not gap them. Starts like a charm.
 

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2002 gmc envoy_slt
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3,203 Posts
Yeah, no matter what brand Iridium plug you use DO NOT GAP THEM, they come pre-gapped and attempting to do so will ruin the plug. AC-Delco plugs just work, its what the engineers designed the 4.2 to run on. Some of the after market plugs work ok, others will have you pulling them within a couple of weeks when they fail or foul. Haven't heard anyone use multi-tip plugs on the 4.2 and have success, so stick to a regular single electrode. If you don't want any issues, get ACD replacements....best $.02 worth of advice anybody on this forum can give you.
 

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Premium Member
2007 chevy trailblazer_ls
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1,422 Posts
Bosch is poor quality!!!!!! I made the mistake of putting the Bosch platinum +4's on my '97 Trans Am years back and it ran great for about a week and got a CEL so I took it to my friends shop where he diagnosed mutiple misfires. Thought maybe the Optispark distributor went bad again(talk about a poor design):ugh: He instead pulled the plugs on the misfiring cylinders and it was 2 of the plugs had broken tips.
 
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