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2004 Chevy Trailblazer LS misfire


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Hello all,

I have a 2004 Chevy Trailblazer LS 6 cylinder 4.2 with 138k miles on it that developed a misfire in cylinder #4.  

I thoroughly cleaned the throttle body....still a misfire.

I changed all plugs, fuel filter, air filter, checked all coils...still a misfire.

I swapped the plug & coil from #4 to other cylinders & had it re-tested...still misfire in #4.  

Used fuel injector cleaner...still misfire in #4.

After all of these steps...I did a computer re-set by disconnecting the battery terminals & using my jumper cables to connect the cables for 30-45 minutes.


Am I right in thinking the problem HAS to be either electrical or compression?  What should my next step be on a budget?

Thanks in advance!

2 Answers

Do the compression test on that cylinder. 


physically check for spark (see FAQ)