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Discussion Starter #1 (Edited)
Hey guys,

I tried to do a quick search on finding any DIY on Ignition coil replacements and/or spark plugs but Im not sure if its the same for 2008 Cad CTS AWD 3.6L w/ DI.

FACTS: Im out of warranty right now, with 88k miles, and Im a newbie. But would really want to try this on my own.

Infos i've gathered is that the OEM Ignition coil is AC Delco D501c. and Spark plugs would be AC Delco 41-990.

What I've read is that I would need the following to work with:

10MM wrench, a 10 MM socket with some extensions and a ratchet wrench, a 5/8 inch spark plug socket

*use dielectric grease to coat the inside of the coil spark plug boot

*lube the coil boot where they slip over the plug
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Questions: Do I need to replace the lower intake manifold?
Does anyone have any videos/recommendations/suggestions on how to properly change the ignition/sparks plugs and recommend anything else necessary to change while under the hood that is intertwined with the ignition?

Anyone help/tip would greatly be appreciated.
 

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08 White Diamond CTS DI RWD FE2 all options
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You are right on tools. You do not need to replace manifold or anything else. In that respect DI engine is great. It took me less than an hour to replace 6 spark plugs and coils. Oh, and I did use OEM's as served me well. God luck.
 

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Discussion Starter #4
My check engine light did come on. But I have yet to go get the codes read. I did buy OBD from amazon, and awaiting to read the code, but from my experience from the first time I had a misfires it was the ignition coil 2 and 5. Just figured Id change them all since Im doing it anyway. Thoughts?
 

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'14 CTS-V LongRoof; '16 ATS-V Sedan,' 04 Trailblazer 4x4; '10 CTS LongRoof gone but never forgotten
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Absolutely change them all at your mileage. I just changed mine this week at 85k plus one coilpack. Was throwing a code.
 

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'14 CTS-V LongRoof; '16 ATS-V Sedan,' 04 Trailblazer 4x4; '10 CTS LongRoof gone but never forgotten
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What you referred to as "ignition coil (2 and 5)." The thingy that gives the spark plug have electricity and sits on top of the spark plug.
 

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Discussion Starter #8
ah I see, thanks. Question about spark plugs. Is ACDelco 41-990 the OEM spark plug? or should I get the genuine OEM spark plug? Is there any difference?

BTW can anyone confirm that AC Delco 41-990 is the right oem spark plug for 2008 cts 3.6L AWD DI? I read somewhere it could be AC delco 41-834?
 

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2008 CTS DI F3 Sport Suspension
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AC Delco 41-990 is the right spark plug. Make sure you use the spark plug socket with the insulator inside. I replaced my spark plugs at 70,000 miles because 2 were bad.
 

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08 White Diamond CTS DI RWD FE2 all options
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This write up is for non-DI engine. With DI you do not have to touch the plenum. AC Delco are the OEM parts. If it was up to me I would replace all spark plugs and coils.
 

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'14 CTS-V LongRoof; '16 ATS-V Sedan,' 04 Trailblazer 4x4; '10 CTS LongRoof gone but never forgotten
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If it was up to me I would replace all spark plugs and coils.
While I don't disagree, you can get by without replacing all of the coils if you need to keep your costs down. Meanwhile, just be prepared to replace them as they fry.
 

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At right about 100,000 miles my 2011 seems to stumble at idle every now and then, nothing serious at all. I just feel it when sitting in traffic and its not constant, just a slight stumble, just once, then it goes away for a minute and does it again. When I push it hard I noticed that the power is not smooth, seems to come on in waves, hard to explain but I am mechanically inclined enough to know its not running at 100%. Could it be plugs or coil packs also ? No codes. Just a seat of the pants diagnosis.
Thanks
 

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'14 CTS-V LongRoof; '16 ATS-V Sedan,' 04 Trailblazer 4x4; '10 CTS LongRoof gone but never forgotten
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Misfire code should show...maybe OBDII time...hook up with one.
 

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2009 CTS Performance Sedan
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FYI everything I have seen on the 41-990 plugs states "gap is preset, do not re-gap".
I've had 4 out of 6 coils / plugs replaced under warranty. I'm just gonna do the last 2 myself this weekend.
I have a small stumble under load but not enough to throw a check engine light and it's driving me nuts.
I'm going to use autozone duralast coil packs for $62 each. They have a lifetime warranty, whatever that means...
Hope they work out. I just don't see how a dealership can justify $400 per coil to replace.

Hammer
 

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FYI everything I have seen on the 41-990 plugs states "gap is preset, do not re-gap".
I've had 4 out of 6 coils / plugs replaced under warranty. I'm just gonna do the last 2 myself this weekend.
I have a small stumble under load but not enough to throw a check engine light and it's driving me nuts.
I'm going to use autozone duralast coil packs for $62 each. They have a lifetime warranty, whatever that means...



Hope they work out. I just don't see how a dealership can justify $400 per coil to replace.

Hammer
That's a good description of how mine feels. I hate to just replace all the plugs and coil packs but I know the car can run better than what it is now.
 

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2009 CTS Performance Sedan
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I changed the last 2 coils and plugs today and the car runs like new again. One thing I also noticed was a disconnected vacuum line. It was the one that attaches to a swivel nipple beside cylinder 6. I am not sure if I pulled it off accidentally or if it was already off. Car was previously feeling very flat at highway speed and had a slight skip when going up a grade. Now it is very snappy and responsive and the transmission even seems smoother. Very simple DIY if you have any mechanical skills.
 

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Discussion Starter #18
Hey guys, I just did the ignition coil and spark plugs, pretty easy on a Direct inject 3.6L engine. Glad I didn't have to touch the plenum. I did need a 10mm wrench to access ignition 3.

Question, I successfully put the wires back together (I hope) but I'm having problems with my navigation screen flickering. I didn't have this problem before the work. Looks like a wiring is loose. Happens when I'm accelerating or hitting a bump? Not sure. Any help would be appreciated
 

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2009 CTS4 Premium & 2012 SRX4 Luxury
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I never trust the whole "pre-gapped" claim. Bought six new 41-990's to do my car and found they had a range of .041 to .045, so it looks like they could be +/-.002 from factory spec. At 70k miles the original plugs weren't horrible, all were within .045 to .050, but I do notice a smoother running engine, particularly apparent in that 40-50mph sixth gear load range.

Would also agree, that aside from a transverse I4, the 3.6 DI has got to be the easiest spark plug change I've ever done.
 

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...aside from a transverse I4, the 3.6 DI has got to be the easiest spark plug change I've ever done.
You never owned an MGB. I could literally crawl inside the engine compartment of that four-banger. Truly a walk in the park. But that was pre-smog/pollution control days. The manual even showed how they installed the pollution control devices in an exploded view, easy to follow - and reverse engineer so you could easily remove that crap. Ahh, another visit in Professor Peabody's WayBack Machine.
 
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