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2004 deville
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ok i had this problem for 3 months now it never changed its always been like this, so here i go, wen i start the car in the morning wen its cold it runs fine as it gets warmer it starts to miss, it will miss just a little here and there and as it gets warmer it starts to miss more and more. wen its all warmed up it just missfires steady,wen i leave a stop sign it jerks like sometighn comes on and off,it wont go at wot at all and if i cruise the road it runs fine but if i press on the gas to much it misses again.
i get the nice p0300 code like yea i know its missfiring but why and were?
so far i changed all spark plugs and they seemed fine,cleaned the tb and censors on tb, tried unpluging the maas air flow s, looked for vacum leak,changed battery, i dont want to change a whole lot of parts for nothing as i am a single parent with 3 very young kids i just cant afford to start swaping parts for nothing,i am inclined mechanicly i built a 72 cuda and a 79 camaro so far built a few engines for em as well but i just cant find this problem .
to me it sounds like someting electrical and im thinking coil pack but my coil packs or 4 in 1 so i dont wanna change em for nothing im sure they are expensive. i was also starting to lean towards bad injectors or feul pressure but why would it be ok wen its cold?
anny help would do at this point im just about put fire to it lol.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Unfortunately our onboard code system will not give the actual cylinder that is missing - BUT you can get that free at an AutoZone, Pep Boys, Advance Auto or other chain parts store. Have them scan the system and the P 0300 C will change to something like "P 0302 C" (depending on cylinder number - the left (front) bank is 2-4-6-8, right (rear) is 1-3-5-7 looking at the engine from the front of the car).

Do you have a steady or flashing SES ? Steady is "miss detected"; flashing is "severe miss detected" and is a cause for cat damage.
 

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White Diamond '03 DHS (with DTS floor shift)
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ok i had this problem for 3 months now it never changed its always been like this, so here i go, wen i start the car in the morning wen its cold it runs fine as it gets warmer it starts to miss, it will miss just a little here and there and as it gets warmer it starts to miss more and more. wen its all warmed up it just missfires steady,wen i leave a stop sign it jerks like sometighn comes on and off,it wont go at wot at all and if i cruise the road it runs fine but if i press on the gas to much it misses again.
Might try checking the fuel pressure. Does it happen when you throttle up in neutral?
 
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