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GMC Forum: Code P0300 HELP!!
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  #1  
Old 06-25-2012, 07:41 PM
cstaebell cstaebell is offline
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Location: O'Fallon, Mo
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Default Code P0300 HELP!!

I have a 1999 Yukon SLT 4X4 with 121,775 miles on it. I recently started having a lot of engine vibration and shaking. I got the good ol' P0300 error code for random/multiple misfire. I changed the spark plugs and wires, and it is still doing the same thing. I am hoping someone may have some advice before I continue repairs. It only does it between 50 - 60 mph and mostly uphill. Lately it has been pretty bad and loses a lot of power when going uphill. If I let off of the gas and ease back into it, it will run better. If I am driving around town at lower speeds and flat terrain, it runs like a dream. But uphill, it is horrible. Any help would be greatly appreciated!
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Old 07-03-2012, 04:43 PM
icanresqu icanresqu is offline
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Default Misfire P0300

I just had the same problem and was going to change cap and rotor while I was checking the cap to make sure it wasn't loose I noticed the coil was extremely hot. Changed the coil and it now runs smoother than before. If the coil gets too hot it means it is getting ready to die. Hope this helps.
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Old 07-04-2012, 11:08 AM
cstaebell cstaebell is offline
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Quote:
Originally Posted by icanresqu View Post
I just had the same problem and was going to change cap and rotor while I was checking the cap to make sure it wasn't loose I noticed the coil was extremely hot. Changed the coil and it now runs smoother than before. If the coil gets too hot it means it is getting ready to die. Hope this helps.
Thanks for the info. I was starting to think that may be the problem. Was it hard to change the coil?
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Old 07-04-2012, 12:55 PM
icanresqu icanresqu is offline
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just have to disconnect the wiring there are two 10 mm bolts to be removed to get the bracket. The icm will be on the same bracket. If the coil has never been replaced before you will have to drill out the rivet to secure the new one with the bolts and nuts that come with it. If you have to drill out the rivits remove the icm to protect it. Then just follow instructions that come with the coil. It should come with new screws and nuts to replace the drilled out rivets. Drove mine after changing coil and it did not miss a lick. Installed a new cap and rotor this morning and drove it a very big improvement. Good Luck.
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Old 07-04-2012, 12:56 PM
icanresqu icanresqu is offline
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oh yeah dont forget to reinstall the icm before putting the coil and bracket back on lol
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Old 07-06-2012, 11:39 AM
cstaebell cstaebell is offline
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Originally Posted by icanresqu View Post
oh yeah dont forget to reinstall the icm before putting the coil and bracket back on lol
I had the ICM checked tested, and it said it needed to be replaced. I replaced it, it runs a little bit better, but still not good. I will change the coil next and see what happens. Thanks for the info!
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  #7  
Old 07-09-2012, 07:01 PM
cstaebell cstaebell is offline
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Originally Posted by icanresqu View Post
just have to disconnect the wiring there are two 10 mm bolts to be removed to get the bracket. The icm will be on the same bracket. If the coil has never been replaced before you will have to drill out the rivet to secure the new one with the bolts and nuts that come with it. If you have to drill out the rivits remove the icm to protect it. Then just follow instructions that come with the coil. It should come with new screws and nuts to replace the drilled out rivets. Drove mine after changing coil and it did not miss a lick. Installed a new cap and rotor this morning and drove it a very big improvement. Good Luck.
How in the heck did you drill out the rivets??? I tried removing the bracket, but that is bolted to the intake manifold, i think, and would make for a lot more work. I can not find a drill anywhere that can get in that small space. With the AC hose right there, i do not know how it is possible to drill i tout from the fender side. From the inside by the throttle, I would have to remove a ton of wiring. Any help would be awesome, because I am stumped!
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Old 07-15-2012, 08:58 AM
icanresqu icanresqu is offline
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just have to disconnect the wiring, there are two 10 mm bolts to be removed to get the bracket and coil off the engine. The icm will be on the same bracket. If the coil has never been replaced before you will have to drill out the rivet to secure the new one with the bolts and nuts that come with it. If you have to drill out the rivits remove the icm to protect it. Then just follow instructions that come with the coil. It should come with new screws and nuts to replace the drilled out rivets. Replace the icm on the bracket and reinstall.
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