: Difficult to change coil pack and spark plug?

11-16-10, 09:05 PM
I went to the dealership today and learned that my #8 cylinder was misfiring and I will need to change the coil pack and 1 plug. The dealership wanted to charge me $330 for labor and material. I wanted to do the work myself. How difficult is is to change as I've done alot of work on my past Cadillac's but I have never worked on my DTS yet. Does anyone have a step-by-step instructional I can go off of, please? Or maybe just a quick tutorial would be much appreciated. Thanks ahead of time.

11-16-10, 09:54 PM
Are you sure you even HAVE a coil pack? I don't think the modern day DTS uses a coil pack. I think they just use a regular coil, which can generally be bought for 35 or 40 bucks.
The last Caddy that had a coil pack would have probably been at least 5 years ago I think. I know the Catera had one. OH!......Maybe you have a deville? That might have had a coil pack and they did have a Deville with a trim level DTS. If you have a deville you are in the wrong forum. If you have a Model known as DTS,It does not have a coil pack.

11-16-10, 10:35 PM
Southern is correct in that the new Northstar engine does not use a coil pack. He is wrong in that it uses a conventional (regular) coil. In the new engine, each spark plug has its own spark coil (there are eight of them). These individual spark coils are mounted directly on top of the plugs. So to remove a plug, you have to remove a spark coil. Can you get to the rear four cylinders (transverse mounted engine, you know)? Personally, I would let the dealer do the job. In any case, a 2006 or newer car should still be under warranty unless it has exceeded the allowed mileage or is in in fact older than 2006 - in which case you are in the wrong forum.

11-17-10, 08:20 AM
The 4 coils bolt on to a bracket, they may have been pricing him the whole coil/bracket assembly plus labor as I have seen them come complete.
If the coil packs are serviced separately (which I am not quite sure of) then it should be substantially less.
My memory isn't what it used to be but I am pretty sure I have replaced one coil on a DTS... if we are talking '06 and up as this portion of the forum would indicate.

11-17-10, 06:51 PM
My wife's 2004 DTS has a single coil pack that provided four ignition coils. This was a single coil pack and was replaced as such if any of the four coils went bad. The "waste spark" method was used so that one of the four coils actually fired two spark plugs simultaneously. One plug fired when the piston was coming up (compression stroke, followed by downward power stroke) while the other plug fired on the exhaust stoke and had no effect. There are still eight (8) cylinders in the current Northstar engine, but eight individual spark coils. They are mounted four to bracket, but there are two brackets (one for each of the four cylinders on each side of the engine - or a total of eight). The waste-spark method is no longer used, and this explains why older Northstars used a single four-coil pack and the newer Northstars use eight individual spark coils mounted directly on the plugs (no high-voltage wires needed).

11-18-10, 08:48 AM
Ted, I am not sure those coil cassetes on the older ones still use waste spark. I think that is only in the older "paired" coil assemblies.
The newer ones use computer controlled coils and they fire individually. I have had many of those cassette type coils fail on only one coil If they were paired this would be almost impossible.

Checking with my parts guy now.
Part number 12594176, coil can be serviced individually, list price is $81.
Changing it requires a torx socket or driver of some sort and about 15 minutes of your life.
#8 would be the most rearward on the left (front) bank of the engine.

11-18-10, 11:48 AM
As I indicated, I was familiar only with 2004 (older Northstars). If there was a different scheme used for "newer" Norhtstars but with a single four-coil pack, I am not familiar with it. My current familiarity is limited to 2008 Northstars so if there are other changes that have occurred since then, I do not know about them. And, I really don't want to know about them. Also, AS I INDICATED, newer Northstars do not use the waste spark method. On my wife's 2008 Northstar there are eight (8) individually computer controlled spark coils. Four for each side, that can be serviced individually.

11-18-10, 01:00 PM
I didn't mean to seem critical, was just trying to clarify.

11-18-10, 06:16 PM
What was unclear about my original post?

11-18-10, 09:16 PM
I have a 2006 DTS. The service rep at the dealership told me my #8 plug was misfiring and the coil pack that operates 2 plugs at a time was also bad. She said I had carbon built up too much on the coil pack. I went ahead and ordered what she told me and I'll find out for sure what it was when it arrives tomorrow. The 1 plug and coil pack cost me $95. She told me the coil pack runs up to the plug wire and then to the plug. She may have been blowing smoke but I'm not sure.
And I have an extended factory warranty and I was told that this wasn't covered under it. Let me know if this sounds strange, please

11-18-10, 10:37 PM
Your 2006 DTS is probably no longer in factory warranty. I don't know what year GM extended the power train warranty from four to five years. If it was after 2006, then your car is definitely out of factory warranty. If it was before 2006 and your car was delivered in 2005, it could still be out of factory warranty. In any case, extended warranties are known for their numerous exceptions. The ignition system might be one of the exceptions in your extended warranty. The outcome of this story is that older cars might cost you money.

A car that still uses the four-coil pack has high voltage wires between the coil pack and the plugs. Otherwise, there are no high voltage wires at all, since the eight coils mount directly on the plugs.

11-19-10, 08:12 AM
Clusco, what warranty do you have specifically? I can run the last 8 digits of your VIN and see if this is a CPO car. If so it should be covered.
I don't think your advisor is lying to you I just think she may not understand the technical operation of this system and may be quoting things she has heard over the years.

ted, regarding what you posted....I had a hard time understanding your point so I was trying to offer some detail.
I have no interest in arguing with anyone or proving anyone right or wrong. You spoke about 3 different ignition systems in one paragraph and I just thought some clarity was needed. The old style coil packs (pre-2000) had two spark towers on one coil. The polarity was always the same and the spark energy went out through one plug and came back through the companion cylinder plug. Since this leaves a spark event on an exhaust stroke they just referred to it as a "waste spark" system. This is not true on either the 2000-2005 model coil cassettes since they have indivdual coils for each cylinder even though they are mounted in 4 coil cassettes. On the older paired coil systems the ICM or ignition control module was in charge of spark control and modified with a signal from the ECM which dictated timing. Modern (post 2000) systems all use coils that are independently controlled by the ECM directly with no ICM at all. The Cassette systems fire one coil at a time and the new COP (coil over plug) systems do as well. The only real difference is that you can service the coils individually rather than having to replace a whole bank cassette. $$$$$$$

I only meant to clarify that the 2000+ ignition systems do not use waste spark because I didn't get that from what you posted, maybe I misread, if so I apologize.

11-19-10, 01:33 PM
Ok I got the part today and I tried to upload the picture it but I was unable to. The part number is: 12594176 and is described as an ignition coil.

So now I know that I have to replace this part and it supposedly fits over the spark plug I just need to know what the steps are in order to do the work. What tools will I need, etc... Does the spark plug just screw in to the motor then the coil snaps on top of the plug and them connect the wiring to the top of the coil plug in?

The #8 spark plug was misfiring and I was told that this plug was located all the way to the left passenger side in the rear...Is this correct?

11-19-10, 01:39 PM
My original post contained information on only two ignition systems, not three ignition systems as you state. Also, as I stated, I did believed that my wife's 2004 DTS used the waste spark system. If it didn't as you say, then so be it. We don't have the car any more, so I don't really care. I only know that the car had a four-coil pack and eight high voltage wires going from the coil pack to the spark plugs. My wife now drives a 2008 DTS and it has individual (8) coils - one for each spark plug. I am done with this thread.

11-19-10, 01:59 PM
One other thing, on trying to remember years back, my description of the four-coil pack and the eight high voltage wires was applicable to my 1995 Eldorado (it had a Northstar engine, too) rather than the 2004 DTS driven by my wife. I still have the Helm factory service manual for both cars, and a cursory examination shows that only the 1995 Eldo used the waste spark method. Both the 2004 and 2008 DTSs have (had) eight separate ignition coils. According to the 1995 service manual, even though the coil pack contained four coils, each coil could be replaced individually.

11-19-10, 06:39 PM

Above is the link to the picture of the ignition coil that I have to replace. It's actually not a coil "pack" as I described in my subject of the post. Can someone let me know the steps to take to change it?

Also, is carbon build up on the coil made by not burning it off by dropping the car into 1st gear at 55 mph and then getting the rpm's up high 3 times a month or so? If so, I take it that once the carbon has set into 1 it's too late to burn it off?

11-20-10, 08:24 AM
ted, seriously I didn't mean to offend or correct anyone. Was just offering some information. It's all good bro.

clusco, on a N* the even numbered bank is in the front, not the rear.
If #8 was misfiring then you replace the one on the front bank closest to the driver's side of the engine.
You just unplug the electrical connection, use a torx headed tool (I forget the size maybe T30?) to remove the one bolt holding the coil in, pull it out, then put the new one in and tighten the bolt. Be sure to keep the green seal in place that is below the coil mounting plate. That helps keep water out of the hole.
Snug up the bolt and plug in the new coil. Wham, Bam, you are done.
Hopefully they diagnosed it right.

11-20-10, 09:28 AM
Thanks Very Much for the info. That's exactly what I needed to know.
Now 1 last question that I have that may sound stupid is, because I've never installed a spark plug before and that #8 plug is bad, do I pop out the ignition coil and then I'll have to unscrew the old spark plug? After I pop out the ignition coil, how far down is the spark plug and what tool will I need to remove the plug?

And just to make sure I'm taking out the correct plug. In you initial post you wrote that... "#8 would be the most rearward on the left (front) bank of the engine." And your last post says to..."replace the one on the front bank closest to the driver's side of the engine".
I know in both descriptions you know what you're talking about and I just want to make sure I'm taking out the correct one. So the coil I will be removing will be the one closest to the front bumper of the car and all the way to the driver's side tire, correct?


11-20-10, 11:23 AM
Ok so for an update...I have just replaced the ignition coil and the spark plug. The plug and coil didn't look too bad so I want to make sure I changed the correct 1. Number 8 was the problem as told to me by the dealership. I changed the coil and plug closest to the front bumper of the car and to the furthest position to the driver's side of the car. I just want to make sure this is definitely the #8 cylinder??? This work took all of 5 minutes which bothers me as to how much the dealership was wanting to charge me ($120 just labor). Please advise me as to if I changed the correct position. Thanks

11-20-10, 12:08 PM
I just gave the car and test drive and I believe I have changed the wrong chamber's plug and coil because it is still jumping. Can someone please post a picture of the #8 cylinder position?

You wrote in your 1st initial post that..."#8 would be the most rearward on the left (front) bank of the engine."
On your latest post, you wrote that..."If #8 was misfiring then you replace the one on the front bank closest to the driver's side of the engine." I know you can see clearly what you're referring to but I am lost. Can you describe it in a little more detail or provide a picture of exactly which cylinder you're referring to?

Also, if it is truly 1 of the cylinders closer to the firewall of the car, how do you get to these as I couldn't see these 4 coils anywhere? Thanks

11-20-10, 08:58 PM
Sorry for the confusion, the "rear" of the block is towards the driver's side. Us mechanics look at the engine, not the car, when we refer to stuff like this.

Typically an engine is looked at from center rear of the engine itself. In a longitudinal mounting the left bank is the driver's bank and the right is the passenger.
In a transvers set up you just turn 90 degrees and look at it from the rear, so standing at the driver's front fender the left bank would be towards the radiator and the right bank is towards the bulkhead.
On Transverse engines we also refer to the left bank as the "front" and the right as the "rear".

Add to that some confusion on the N* because banks 1 and 2 are swapped from the way most people think.
The odd number cylinders are on the rear or right bank, and the evens are on the front or left bank.

Hopefully that is a little more clear. Sorry for the earlier confusion.

To change the rear coils you just have to remove any covers over the top. I don't do many so I don't recall what is on there and if you have AIR (a big check valve) you have to remove the valve first and then take the other stuff off. Otherwise it would be the same, however you don't know which one is misfiring.
It sounds as if it may have been misdiagnosed.

11-21-10, 02:20 PM
A factory service manual would remove all of the questions and misinterpretation being provided.

11-22-10, 01:27 PM
Ok after that explanation I'm possibly more confused than before. I know for sure that a code was pulled up that the #8 position coil and plug was misfiring. Let's make this as simple as possible, please, before my head explodes. Below I've provided a series of numbers from 1-8. The left side of my number diagram represents the passenger's side of the car while standing in front of the car staring at the windshield. Plese put correct my cylinder numbering positions accordingly. I will be very appreciative:

left side{____}right side
1 3 5 7
2 4 6 8

11-22-10, 09:15 PM

#8 is the cylinder on the bank you can see in the foreground, farthest to the right which would be vehicle left, closest to the radiator.

Blown & Injected
12-07-10, 03:41 PM
Clusco, what warranty do you have specifically? I can run the last 8 digits of your VIN and see if this is a CPO car. If so it should be covered.


May I e-mail you with my VIN? It is an 06 DTS VIN9, Certified, but I do not know when the time is up and there are some issues I want to get taken care of before my time is up.

And so this is not a total hijack. Are those firewall side plugs hard to get too - any tricks?