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Discussion Starter #1
So I just spent longer than planned changing my spark plugs because one of the spark plugs had oil on it when I took it out. (Driver side) so I had to order the seals and valve cover gaskets.
Long story short, I got everything put back together tonight. (I’m pretty sure I didn’t miss anything, I’ll double check tomorrow when there’s light out) I go to start it up and it hesitates and kinda sputters at first and then it starts. Was idling pretty rough and the check engine light comes on after a couple mins. the longer I left it on the more it sounded like it was loosing power. I left it on for about 5 mins waiting to see if it was going to stop but I turned it off before i could find out.
Waited about another 5 or 10 mins and started it up again. It still hesitated a tad bit but it did start up a lot faster than the first time. Was still idling rough but I noticed it slowly going back to normal. Waited a few more mins and it’s started idling smooth but the check engine light is still on and if I get out and go to look under the hood I feel like I can hear things that weren’t there before and they don’t really sound like good things to me.
Turned it off again and decided to go for a little drive around the residential area about 5 mins later. start it up and it starts up right away this time. Still check engine light on. so I start driving and it just doesn’t sound or feel right to me.
Any ideas what could of happened?
 

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2007 CTS 3.6 >129k miles
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If all you did was the plugs/seals and VC gaskets, my first thought is that you have a vacuum leak (possibly a hose is loose or disconnected), the intake plenum gasket is not sealed, or the MAF sensor is not connected. Lots of little things that can cause rough idle.
 

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2006 Cadillac CTS [] 2008 Cadillac DTS
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Similar to what argent said, if you used pre-gapped plugs that were other then ACdelco then that is 100% your problem. I'm having the same issue right now and replaced them OE Acdelcos with a set of Bosch after the valve cover replacement. In which just ran terrible. I'm installing the backside ACdelcos today with a entire new set of coils since those had some oil on them too.
 

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Discussion Starter #5
Assass
If all you did was the plugs/seals and VC gaskets, my first thought is that you have a vacuum leak (possibly a hose is loose or disconnected), the intake plenum gasket is not sealed, or the MAF sensor is not connected. Lots of little things that can cause rough idle.
so I took it to get scanned with the ODB2 this morning and I got 2 new codes along with 4 other ones that were already there before I did the job. P0305 and p0300. One is telling me there’s a misfire and the other is telling me wich cylinder is misfiring. Cylinder #5. If I counted the cylinders right then that’s the one that had oil on the spark plug when I changed it.
 

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Discussion Starter #6
Did you check the plug gaps or just install them right out of the package?
Took it to get scanned this morning and got two new codes. P0300 and p0305. One telling me there’s a misfire and the other is telling me wich cylinder is misfiring. Cylinder #5. And that’s the one that had oil on the park plug when I changed it.
 

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Discussion Starter #7
Similar to what argent said, if you used pre-gapped plugs that were other then ACdelco then that is 100% your problem. I'm having the same issue right now and replaced them OE Acdelcos with a set of Bosch after the valve cover replacement. In which just ran terrible. I'm installing the backside ACdelcos today with a entire new set of coils since those had some oil on them too.
Took it to get scanned this morning and getting two new codes. P0300 and P0305. One telling me there’s a misfire and one telling me wich cylinder is misfiring. Cylinder #5. And that’s the one that had oil on the spark plug when I changed it.
 

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2007 CTS 3.6 >129k miles
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I would start by swapping the coils between cylinders 3 and 5 and disconnecting the battery to clear codes. If the misfire shifts to p0303 then the problem is the coil.
 

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Discussion Starter #9
I would start by swapping the coils between cylinders 3 and 5 and disconnecting the battery to clear codes. If the misfire shifts to p0303 then the problem is the coil.
Damn that would of been a good idea to at least eliminate that possibility. I already dropped it off at a shop to get checked out.
 

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2006 Cadillac CTS [] 2008 Cadillac DTS
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What's the mileage at? Im guess around 130k due to the valve blowing, I would just replace the entire set of coils and plugs
 

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Discussion Starter #11
What's the mileage at? Im guess around 130k due to the valve blowing, I would just replace the entire set of coils and plugs
It’s at about 176k. I’m really hoping it something simple. The coils are what lock the spark plugs in place right? If it was that wouldn’t I have had the code coming up before I did the job?
 
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