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I have o4 cts 3.6 120,00 car runs great but sometime i get a blinking check engine light and the car misfires shakes like crap runs through gas fast, runs super ruff. It will run perfect then in a second start misfiring it goes back and forth all the time might run great one day then missfire the other it changrs back and forth its crazy any ideas? Possible coil pack? Also just replaced battery and the volts are good but sometimes i get a service charging systems warning. I have brand new battery. If any caddy experts on here can give me some advice id greatly aprecheate it. Thanks
 

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08 STS 1SG HUD ACC F55 AWD, 08 STS 1SG Platinum HUD ACC F55 RWD
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Get the codes read to find out which cylinders are misfiring (free at most parts houses). Replace all the plugs (look at old spark plugs for possible problems) and move the coils from the misfiring cylinder to another cylinder (preferably 1,2,5 and/or6). If no misfire after - Grats - you fixed it. Test drive and get the codes read again. If the misfire moves to a cylinder you moved a coil to - replace that coil. If the miss does not move check the wiring to that coil.

Clean and tighten up the battery connections and remove and clean the grounds on the other end of the negative battery wire (one on the shock tower and one connected to the engine).

Problems could be other things but these are the cheapest/quickest/easiest possible fixes. Repost back to us the results so others benefit from your experience. Oh - and when you post the code numbers, list what the number means so that all do not have to look it up. Make it easy for others to help you. Good Luck and Welcome to the forum.
 

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Check codes at an autoparts store. But if it's running rich in gas than that could mean a clogged air filter. So I'd do the spark plugs with oem plugs and replace the air filter. BTW the plugs are a pain to get to. The book calls for 3 hours per side but those of us who've done it before can do the whole job in 1.5 hours.
 

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Discussion Starter #4
I have o4 cts 3.6 120,00 car runs great but sometime i get a blinking check engine light and the car misfires shakes like crap runs through gas fast, runs super ruff. It will run perfect then in a second start misfiring it goes back and forth all the time might run great one day then missfire the other it changrs back and forth its crazy any ideas? Possible coil pack? Also just replaced battery and the volts are good but sometimes i get a service charging systems warning. I have brand new battery. If any caddy experts on here can give me some advice id greatly aprecheate it. Thanks
Ok thank you the air filter is brand new so it's not that I'm thinking plugs wires or a coil pack as soon as I get some time I will break it all down and die septic I will get back to you guys thank you for the advice
 

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2004 CTS Lux Sport and 2014 ATS 2.0T AWD Lux
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Sometimes it's just bad coils. My originals lasted 100K miles. The mechanic replaced with Bosch OEMs but one failed after one year and another failed after the second year. After replacement, late last year, things hae stabilized. And yes, the associated spark plug had to be replaced also.
 
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