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2004 chevy trailblazer_lt
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997 Posts
I cant hook up the OBD-2 to read it I guess I have a fuse out somewhere. anyone know where that fuse is??? any help would be greatly appreciated
Fuse #13, underhood fuse block. It is the fuse for the cigarette lighter socket, and also powers the OBDII connector.
 

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2004 chevy trailblazer_ls_ext
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1 Posts
Just recently fixed my random misfire 04' trailblazer 4.2l ,200k miles. First I inspected all spark plug holes, used my camera to take pictures of cylinders 5 & 6. #4 was sitting in an oil bath. The camshaft cover was leaking. I purchased a new gasket set, Felpro $20 Autozone. Removed negative battery cable, airbox, throttle body (clean this while your in there) it will help with rough idle, alternator, pcm, intake manifold. These bolts were a fuc#%r. Everyone else said the fuel lines needed to be removed to get this out. I didn't have the tools so I found a way, if you remove the electrical connector from the top of the manifold, it's close to the firewall. This will give you just enough clearance, it still requires some cussing and forcing though. Next I removed the camshaft cover, removed the old gaskets, cleaned mating surfaces with toothbrush and brake parts cleaner. The teardrop gaskets that seal the spark plug reservoirs fit great, but the large gasket would not fit.... Ahhhhhh. I decided to reuse the original. In the future I'll not buy felpro, maybe OEM. I also replaced the intake gaskets. Next I cleaned any oil from spark plug reservoirs. Replaced all spark plugs and boots. I put everything back in reverse order. Started up with the same misfire. I purchased 1 coil $62. Installed on suspect #4 cylinder. This fixed it, oil must have shorted the coil to failure. No more misfire or check engine flashing. Entire job took me about 10 hours, 3 days time after work. It felt good to cancel the scheduled diagnostic check at the shop. I decided to post after realizing that nobody posts their fix. I hope this helps.
 

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2004 gmc envoy_slt_xuv
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1 Posts
My 04 Keeps throwing the Random misfire too... I've replaced the plugs twice (I didn't gap them right the first time, got the A/C Delco plugs now), and all 6 coil packs. It ran fine for about 2 months and it went right back to the misfire! Got a code for #4, switched it with the #2 coil and it now is Random.....

And all this with only 65k on it! I'm hoping the head hasn't gone bad...
 

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2003 chevy trailblazer_ls
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19 Posts
Got a P0300 (with no other codes) yesterday about 2 miles from the house on the way home from the supermarket. Was able to limp it home. Cat probably got pretty hot. Exhaust stunk like rotten eggs. I do have HP Tuners for my 06 Silverado so I used it to check for misfires this morning. It showed #4 missing. I swapped coils between #3 and #4 cylinders and the missing moved to #3. O'Reilly's had a lifetime warranty coil for $65 so picked up and popped it in. No more misfires. Car seems to run fine now... hopefully no damage to cat. Weird I didn't get a P0304 code... but maybe I didn't drive it long enough or the computer to dial in on the misfire location(?).
 

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05 trailblazer replaced transmission now misfire

my issue started when i changed my transmission. took it off the hoist and now the thing is p0300. did i miss a ground or something on the bell housing. this is the only code im getting. Any help Please
 

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1 Posts
Just recently fixed my random misfire 04' trailblazer 4.2l ,200k miles. First I inspected all spark plug holes, used my camera to take pictures of cylinders 5 & 6. #4 was sitting in an oil bath. The camshaft cover was leaking. I purchased a new gasket set, Felpro $20 Autozone. Removed negative battery cable, airbox, throttle body (clean this while your in there) it will help with rough idle, alternator, pcm, intake manifold. These bolts were a fuc#%r. Everyone else said the fuel lines needed to be removed to get this out. I didn't have the tools so I found a way, if you remove the electrical connector from the top of the manifold, it's close to the firewall. This will give you just enough clearance, it still requires some cussing and forcing though. Next I removed the camshaft cover, removed the old gaskets, cleaned mating surfaces with toothbrush and brake parts cleaner. The teardrop gaskets that seal the spark plug reservoirs fit great, but the large gasket would not fit.... Ahhhhhh. I decided to reuse the original. In the future I'll not buy felpro, maybe OEM. I also replaced the intake gaskets. Next I cleaned any oil from spark plug reservoirs. Replaced all spark plugs and boots. I put everything back in reverse order. Started up with the same misfire. I purchased 1 coil $62. Installed on suspect #4 cylinder. This fixed it, oil must have shorted the coil to failure. No more misfire or check engine flashing. Entire job took me about 10 hours, 3 days time after work. It felt good to cancel the scheduled diagnostic check at the shop. I decided to post after realizing that nobody posts their fix. I hope this helps.
Thank you so much for posting this :)
 
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