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2002 chevy trailblazer_ls
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15 Posts
Discussion Starter · #1 ·
I changed the spark plugs, made sure the gaps were all right, cleaned the throttle body while in there (made sure I paid close attention to the sharp edges, thanks to those who suffered to tell us to beware), now my gas mileage has gone down considerably. Any ideas?:bonk:
 

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2002 chevy trailblazer_ls
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I changed the spark plugs, made sure the gaps were all right, cleaned the throttle body while in there (made sure I paid close attention to the sharp edges, thanks to those who suffered to tell us to beware), now my gas mileage has gone down considerably. Any ideas?:bonk:
Figure I'll be the first person to say that you should (if you didn't already) disconnect the negative battery cable for 30 minutes to reset the computer's adaptive settings.
 

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2002 gmc envoy_slt
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3,203 Posts
First question is did you replace the plugs with AC Delco or an after market brand? - The I6 doesn't seem to like after market plugs very much.

Secondly, when you verified the gap on the plugs, you didn't attempt to adjust them did you? - The iridium plugs should NEVER be re-gapped. The gapping process can actually damage the plug and cause loss of power/performance or fuel economy. (Its a very thin coating on the plugs that is easily damaged).

How does it run other than the fuel economy? Could it e a batch of E10 or some other cause?
 

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2002 chevy trailblazer_ls
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Discussion Starter · #4 ·
I used the AC Delco iridium, no I just placed the gap tool next to them to make sure they weren't bumped in transit. I did not try to re gap them. The negative cable was disconnected for a couple hours while I replaced the plugs. Several stops in the process. Other than the gas mileage it runs great, no more hesitation or missing apparent. I ran some Lucas through it. I cannot find any gas around that is not 10% ethanol. I will see how it does once the tank with the lucas goes through. I will check back periodically. Thanks
 

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2007 chevy trailblazer_ls
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1,422 Posts
It could be possible lazy O2 sensors. Only way to see that is to hook up a scanner. Also hows the air filter looking? Or lastly it could be that troublesome leadfoot I hear about.:woohoo:
 

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2002 chevy trailblazer_ls
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Discussion Starter · #6 ·
07Blazer man: Hooked it to a scanner, no codes pulled. Air filter changed about 5K ago. The lead foot is not a problem, (pawpaw driving, sorta) I think (at least I hope) it is bad gas. Will know more when I am done with this tank. Someone mentioned a possible fuel filter issue, checked it out, still have the original after 135K miles. Could this be a possibility?
 

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2003 chevy trailblazer_ls
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5,268 Posts
even if its not the issue--- change it.
Theyre only about $20 I think.. And very easy to change on the early Trailvoys
 

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2007 chevy trailblazer_ls
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1,422 Posts
Just to clarify not a scanner for codes but a scanner that shows realtime data of the O2 sensors. You can have a lazy O2 that doesnt throw a code but will rob mpg. Good luck.:)
 
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