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Discussion Starter · #1 ·
alright have 2008 impala 3.9l v6 dedicated cng (compressed natural gas) its has 65k miles orignally state owned sat alot of course but anyway its hard to start 50 degrees or colder might cause of cng but it misses bad when cold clears up after rev few times and runs good warmed up i havent messed with plugs or wires or anything i do have torque pro app... shows misfire current and history shows cylinder 3 and 5 misfire lots and 1 sometimes soo the back 3 cylinders im getting code po300 random misfire its also going neative fuel trims... like -10 -11
 

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When's the last time the plugs and wires were changed? Unfortunately I can't speak to the CNG part of it :(
 

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Discussion Starter · #3 ·
to my knowledge the are orignally i can tell the wires are i assume the plugs are too i know it has 65k miles i dont know how long there suppose tolast ... cause ive always had high mile vehicles soo i always tune up when i get them usually i do know the active fuel mangement is disabled
 

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Usually they are good for 100,000k miles but you've got some years behind yours. Could be the issue, maybe not, wouldn't hurt to switch them out.
 

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Discussion Starter · #5 ·
yes very true and i know cng is 130 octane equal soo it needs very good spark
 

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130 octane... Yeah I'd say check those plugs. Could be your issue. I'm also assuming your vehicle has a different owner's manual than the standard impalas which may cover the specifics of CNG maintenance. If not, I'd see if you can find one somewhere. I couldn't locate one after a quick google search, so a dealership may be your best option for that.
 

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Discussion Starter · #7 ·
ya same owners manul as normal car came from factory as flexfuel then about 2k miles it was coverted by natural drive/tulsa gas technologies soo been dedicated cng since almost new ya cng is 130 octane its looking like plugs then is that why i have negative fuel trims?
 

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Discussion Starter · #9 ·
actually im new to cng i dont know where these filter located i need help to know and where would i buy the filters? how to change them? and i did a tune up plugs and wires i did have 1 cracked plug it improved running and idling when warm but still rough cold and i get random multi cylinder misfire next im going to try checking for vac leaks i get mis on cylinder 1, 3,5,6 just random
 

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Discussion Starter · #10 ·
also im using the torque pro app and when driving i got negative fuel trims at idle but when i get on it they go to 0 or close but when i let off the fuel trims goes back to negative
 

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No pic. Maybe try again?
 

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The thread I linked to has instructions on resizing pics. If you use Tapatalk or a mobile app to access the forum, it should auto resize it. If not, you should have some picture program on your computer that can resize.
The thread says what size the picture needs to be.
 
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