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2004 chevy trailblazer_lt
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What spark plugs did you use and what brand of ignition coils?
 

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2004 chevy trailblazer_lt
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Which Delco plug? The 4.2 l engine in theses critters are extremely picky about what plugs go into them. Most of us on this forum reccomend the ACDelco 41-103 plug. Also, Ultra Power Coils are likely a generic Chinese coil that are made with zero quality control and I would not be surprised if one or more of them were either dead on arrival, soon to be dead, or only marginally working. There is a reason why they are so inexpensive - they were likely manufactured using poor quality copper and 3rd rate electronics.

I can appreciate you wanting to save some money, but please don't skimp on ignition coils because if you do, the odds are that they will leave you stranded with towing bill.

You should consider returning them as defective and ordering one of the following brands, ACDelco, Delphi, or Standard Motor Products (non T series)/BWD (non-P series). Those are quality parts that will not leave you stranded.

Also, what year is your vehicle and please confirm that it is the 4.2 l I6 engine.

Oh, and WELCOME to the forum!!!!!
 

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2004 chevy trailblazer_lt
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I forgot to ask, before you replaced the spark plugs and ignition coils, how did it idle?
 

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Discussion Starter #6
Which Delco plug? The 4.2 l engine in theses critters are extremely picky about what plugs go into them. Most of us on this forum reccomend the ACDelco 41-103 plug. Also, Ultra Power Coils are likely a generic Chinese coil that are made with zero quality control and I would not be surprised if one or more of them were either dead on arrival, soon to be dead, or only marginally working. There is a reason why they are so inexpensive - they were likely manufactured using poor quality copper and 3rd rate electronics.

I can appreciate you wanting to save some money, but please don't skimp on ignition coils because if you do, the odds are that they will leave you stranded with towing bill.

You should consider returning them as defective and ordering one of the following brands, ACDelco, Delphi, or Standard Motor Products (non T series)/BWD (non-P series). Those are quality parts that will not leave you stranded.

Also, what year is your vehicle and please confirm that it is the 4.2 l I6 engine.

Oh, and WELCOME to the forum!!!!!
 

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Discussion Starter #7
I used 41-103 replace them first no change so I changed all coils still no change it started to run like crap in the rain
 

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2004 chevy trailblazer_lt
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Double check that the coils are indeed seated onto the spark plugs properly, and 2nd, make sure that the wiring connectors to the ignition coils are seated properly. Once in awhile, the coils do not seat properly onto the top of the spark plus and then the engine runs like crap.
 

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2004 chevy trailblazer_lt
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OK, thanks for the information.

As I suggested, double check that the ignition coils are properly seated, and that the wiring connectors to the ignition coils are also properly seated.
 

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I forgot to ask if you have a code scanner/reader?
 

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OK, thanks.

If reseating the coils and electrical connectors do not help, can you monitor misfires with your code reader?
 

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2005 gmc trailblazer_ls
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When you replaced the old spark plugs, how did they look like? Are any of them where oily? If answer is yes you may check the compression. Of course assuming that's your spark plugs and coils are correct and properly installed.

Sent from my SM-G955U using Tapatalk
 

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Replaced plugs and coils still have code idles like crap
I just went threw this on my 03tb. It was miss firing code po300 it ended up being multiple coils out #3 #6. I started it up pulled the wire harness off of each cylinder putting it back on paying attention for a difference in sound or vibration did that starting on cylinder 1 and worked my way back. That might help you find what cylinders are not firing
 

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I had this issue awhile back. There were no code present; it just idled rough. Threw new AC Delco plugs at it and Delphi ignition coils. It turned out to be a dirty throttle body. The butterfly in the throttle body looked fine, but when I pulled it off, the back side was covered in soot. I thought it was crazy that would make it run so poorly, but that was it. So, maybe check the throttle body? Good luck.
 

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What spark plugs did you use and what brand of ignition coils?
Did you gap your spark plugs correctly if they are gapped incorrectly then the spark will not be able to ignite the fuel in the cylinder if I recall correctly they should be gapped at .36 to .5 for proper use I did not know this until I had to do my spark plugs if you need a tool to get it its like 2 dollars at most of not all auto part stores if your in the U.S. if your in Canada then they are probably closer to 10 dollars just ask for a spark plug gapping tool they will know what your looking for and just follow the numbers on it to gap your plugs if you over shoot the gap use a hard surface to push the prong back down
Replaced plugs and coils still have code idles like crap
 
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