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Discussion Starter · #1 ·
Hello ever one.
Was having a miss fire on the TB, so went to Autozone to get scaned and they told me they cant loan the tool out any more.:mad:
I all ready made a post about that. So I went home to check the plugs and thought I need new plug any way( 118000mil on it).
Got the AC 41-103, broke on plug trying to gap it :laugh:
There are 2 bad parts to this. Plug 4 and 6 where wet with gas, and I mean wet. so I guess I need two coil packs. I'm sure this is my miss fire.
The real bad was plug 2. It came out very hard,and would not take the new plug. Had my dad come over to check it out, we played with it for 3hr.
We would put it in a little at a time. If it got hard we would pull it out.
At the last time taking it out, the top thread was flat and we know it was now or never. I think its about 1/2 to 1 thread out of being full in.
We are pretty sure that this was cross threaded at the factory, the other 5 were easy as pie, even #6, so we were basically re-threading the head :ugh:
Fun huh.
So I know at 200,000mil+ I will just put a new motor in, why waste the money to get the head pulled off.

Thanks for letting me ramble

Doug
 

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2003 chevy trailblazer_lt_ext
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Retap the hole using the same thread pattern. To test your coil packs, insert a NEW plug into the coil pack, hold it close to a metallic part of the engine, and have someone crank the engine. It should spark, if it doesn't, then your coil pack needs replacing :)
 

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Discussion Starter · #3 ·
Thanks for the info ieatglue on how to test the coil pack.
All try it tomorrow after work and let every one know

Doug
 

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2003 gmc envoy_slt
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7,190 Posts
You didn't say, so I'll post just in case. Never try to remove a plug from a hot engine. Specially an aluminum head (like we have). And if you re-tap the hole, dip the tap in grease first to catch the metal shavings.
 

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Discussion Starter · #5 ·
Hello again every one.
Here is the update.
The miss fire is hit and miss, it will be idling nice and then you can watch and hear it start to miss fire. Took it for a spin and same thing it would run fine and them miss. The CEL would blink like a mad man when it would miss, when it would stop the CEL stays on. I still have not had the code read, got to find a place to do it for free.

The engine was dead cold when I change the plugs, witch is why I believe that the #2 cylinder was cross threaded when the engine was built.
It may be a little bit be for I fix it just because of money being tight,
so this thread my be idle for some time, but will report back when it is fixed.

Doug
 

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2002 chevy trailblazer_ltz
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Just a few comments about changing plugs & coil packs:

I had an intermittent miss similar to what you described, and I ended up going on ebay and buying a complete set of "slightly used" coil packs from a dealer pull-out engine that had low miles. Cured the miss instantly.

Also, when you put the coils back in, be careful to put them in straight....it is possible to have them a little crooked, and the spring in the end of the pack won't touch the top of the plug terminal....instant miss situation....that happened to me when I changed the plugs.:bonk:

Oh, and for the most part, new plugs are already pre-gapped. If you DO check them, as long as their close, leave them alone....the engine won't know the difference of a few thousands of an inch, believe me. :no:
 

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2006 chevy trailblazer_lt_ext
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Was I was working at a shop we found that Gm didn't do their homework when they announced the 100,000 till tune up. We had too many issues of plugs that were seized to the head, or more often plugs that never made it to 100,000. Best advice put some anti sieze on your plugs when you reinstall, torque them correctly (torque wrench) and change them before 100,000. usually every 30,000.
 

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2005 chevy trailblazer_ls_ext
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Was I was working at a shop we found that Gm didn't do their homework when they announced the 100,000 till tune up. We had too many issues of plugs that were seized to the head, or more often plugs that never made it to 100,000. Best advice put some anti sieze on your plugs when you reinstall, torque them correctly (torque wrench) and change them before 100,000. usually every 30,000.
:iagree: I changed my plugs around 50K. They LOOKED good, but I had a very noticeable loss in performance. No missing, just not as much power as it used to have.
I had no trouble with the plugs coming out - came out very easy.
 

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2003 chevy trailblazer_ls
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You could always helicoil the plug threads. Works very nicely. :D
 

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Discussion Starter · #10 ·
Hi Again every one.
I got the coil plugs from ebay today, and just got done putting them on.
One was new and one was used, the used one looked better then the one's on the TB. I put them on #4 and #6 started it up and still had a miss. :(
I left it running and stated to unplug the wires, got to #3 and that was the one.
Here is the interesting part. I took the old coil plug I just pulled off and put it in #3 and it works. :weird: Took it for a drive and it runs like a champ:thumbsup:

So it look's like I had 3 bad coil packs, but one started to work again.
I will buy another one off ebay just in case #3 start to act up.

Thank you for all your help, I hope this can help some one else in the future.

DaCarmack
 

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2002 gmc envoy_sle
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8 Posts
Replacement Spark Plugs

Lots of discussion on iridium plugs. I have always gapped my plugs by bending the electrode - (metal piece bent 90 degrees off the plug) and I have never had a problem. I bought a new set of Delco iridium plugs and all of them were at the wrong gap, as are almost all of the plugs I have ever purchased. Bending the electrode and using a flat guage worked without incident. The round guages are not particulary accurate. Just use common sense and don't force anything and adjusting the iridium plugs should not be a problem.
 
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