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2002 GMC Envoy SLE
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Discussion Starter #1
I am new to this site. I have checked it out before and thought this would be the best place to look for help. I have a 2002 Envoy. It started missing, I changed plugs and replaced all coil packs. still have a random misfire. The CEL is on and flashing. I know that I can't drive it.
Did a compression test and all cylinders have between 178-184. Please, what is my next step? I am using my mothers old ragged out pickup right now but I really need to get mine running . I need some advice.
 

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2004 gmc envoy_slt
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2,468 Posts
How many miles? Did it start missing after a fuel fill? Do you have access to a scan tool that can read live data (this can show where the misfires are)?
 

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2002 GMC Envoy SLE
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9 Posts
Discussion Starter #3
How many miles? Did it start missing after a fuel fill? Do you have access to a scan tool that can read live data (this can show where the misfires are)?
No, it wasn't after fueling. Just got in it one day and after driving several hours, the light came on. The next day drove to town and then started noticing slight miss. Continued to get worse. About a mile from the house light started flashing and bad miss. I have a reader that I got off ebay and it only shows the one code, P0300. I Changed all coils and all plugs. Plugs are 41-103 AC delco. I also cleaned the TB. Today I did the compression test. So what is next? Trying to do it myself to save as much money as possible since I am disabled and on fixed income.
 

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The flashing CEL is trying to tell you that the misfire is severe enough to destroy the catalytic converter.

You need to run a live data stream to see what's going on, not what has happened!
 

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2004 gmc envoy_slt_xuv
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11 Posts
It was 2 bad plug wires on my 5.3L. Took to dealer and they could not figure it out. Changed wires and all is still good.

Did burn out both cats in the process, though.
 

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2002 GMC Envoy SLE
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Discussion Starter #7
The flashing CEL is trying to tell you that the misfire is severe enough to destroy the catalytic converter.

You need to run a live data stream to see what's going on, not what has happened!
Yes, I understand that. I live about 20 miles from town and I don't think that I should drive it that far and possibly burning up the cat.
 
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