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Misfire - Plugs or coil pack?

88K views 80 replies 39 participants last post by  Long 
#1 ·
Hello all,

Ever since I got my car with 5xk miles it has had a slight miss, but 3 different dealership visits told me there was no miss. I recently got a check engine light that required warranty replacement of the secondary water pump. I had just started getting the miss much more noticeably, and they assured me, somehow, this would fix the miss (still popping no codes for that). Well, picked it up, miss remains, took it back and they inform me though the car is giving ME no codes, it did show them it had a miss due to plugs needing replacing (now at 8xk miles). I went on home and a few days later and now I am getting a violent miss and finally popping a code on cylinder 6. It increases in severity with temperature. In the 30s it is really bad, 50s and 60s like we will have this week ease it greatly.

My question is, is there any way to deduce whether it is a coil pack or wires? If not, should I change plugs and hope or is it much easier to go ahead and replace packs while I'm at it and what is the cost? or maybe all plugs and just the coil pack on the cylinder in question?

Thanks in advance.

-Ryan
 
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#2 ·
Ryan, I realize you're looking for DIY advice from owners, but I wanted to let you know I'm available to work with your dealer towards a resolution at any point. I'm happy to contact them on your behalf and follow up for you, so please email me at Katie_Lucille@gmexpert.com for further assistance. I'm so sorry to hear about your continued frustration with this concern!

Katie
Cadillac Customer Service
 
#3 ·
I'm not sure of the set up but, The easiest way DaPurple is to switch coils. Numer 6 with the another coil. If the miss follows the coil, its the coil, if it stays on number 6 cyl it may be cracked plug, injector or mechanical, but not the coil.

Replacing the coils is expensive relative to taking out a pretty girl.

I would go with replacing the plugs, switching the coils and go from there. Its what I would do. GOOID LUCK!
 
#5 ·
Like they said, first change all plugs, then move coils to different sides, see if the miss moves. If it does, then just a bad coil. IF it stays, then it may be an injector, swap the injectors around to the other side, if it still is there, it could be a valve spring, or valve, or bad wiring, or piston. Do a compression and leak down test on the cly, if it is still there,
 
#6 ·
I just had this problem on my 2009 CTS DI AWD and it ended up being the plugs. The firing order is 1-3-5 on drivers side and 2-4-6 on the left. You can start by just reseting your codes, swaping coils and seeing if the miss moves. Just remove your oil cap and pop the engine cover off then pop the plastic covers on both sides off for more room. If you have any question or want some photos just let me know.
 
#7 ·
Funny because I am getting something similar. My car is missing or acting like its missing when under a load and light gas, like maintaining speed and going up a hill. I took it to the dealership and they said it's not throwing any codes. I guess it might be the plugs? It only has 55k on it and I know the plugs are supposed to be good to 100K
 
#11 ·
Where did you hear it? It is an interesting information but to believe it I woul dneed evidence. That said I had a coil going bad I think at 50k or something similar. Reading this board it would appear that many people had issues with either coils or plugs.....interesting.
 
#24 ·
This happens to me too.
Took it into the dealer a while back; they said they fixed it by reprogramming.
Every time I hear that I laugh.... Still does the same thing.
Looks like a DYI project for summer.

I just might change everything. Was it easy to change all plugs + coils? Accessible?
Can anyone recommend better coils + plugs.
 
#26 ·
I have had many vehicles and have been driving for 35 years and have never had a coil go out until I bought my 2008 CTS4. At 66k my car started running like crap and had a hard time going up hills. It was jerking and you could hear a muffled backfire. Dealer found the number 4 coil had gone out. replaced it and ran like new again. The check engine light never came on. Now at 146k I strarted noticing lower gas economy then a very slight jerking on acceleration mostly when it was cold. this progressed but not as severe as before. Took it to the dealer again and yep, coil but this time the computer wouldn't pick it up and the cars ECM showed no codes. I had to drive the Tech around with his computer hooked up until the jerking started and then he saw misfires on 3 and 6. after further diagnostic it was the coils. Changed them out and runs like new again. So it appears a coil can go completely out like my 1st one and easily be detected or they can go partially out and be harder to detect but eat away at your fuel economy and gradually get worse so you know you have to take it in. The dealer suggested I replace all of the coils. They charge 400.00 per coil to install stating the intake manafold has to be removed to get to the coils. I think its rediculous that these coils malfunction like this. The picture I attached is one of the coils I had replaced today. You can see rust or dirt on the rubber seal that fits into the chamber so it looks like moisture gets past this seal and could be shorting them out. Auto part
 
#27 ·
To the guys who have changed the plugs, did the geniuses at GM torque these plugs down to 100lbs or something? I just tried to get on with a 3/8 ratchet and I applied double the force I've EVER applied trying to loosen a plug and stopped for dear of breaking something because NO plug should ever be that tight!
 
#29 ·
I have had three coils go bad and the symptoms were always progressively the same. Weak power at 2500, some hesitation, then finally starts to miss at 70 cruise with light throttle. Finally gets almost constant. Doesn't set check engine light until it misfires badly and like three times in a row.
Note that my coils were damaged by a disconnected vacuum hose - air leak. After that was fixed it still took last 2 coils another 6 months to fail.
Runs like a new car with all good coils!

----------

So for a long time I had no codes and it still ran badly.....
 
#30 ·
I have 185,500 on my CTS and it is doing the same thing, no codes at dealership. They were able to get one cylinder to misfire, I was close to a tune up so I had them replace all the coils and plugs and I am still having the same misfire under acceleration. Mainly after the motor has been running for awhile. Not sure what my next step is to do, the dealership doesn't seem to know what to do either.
 
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