: 08 CTS DI plug change

06-14-13, 01:47 PM
I've seen a couple of threads on changing the plugs on non di engines that require the removal of the plenum. I've heard that the di plenum is narrower and doesn't need removal. Is this just a quick removal of coil pack and straight to the plug? Other than blowing out the chamber bc it's recessed, putting anti seize on the threads, wearing goggles, and torquing to specs...is there anything else I need to know or worry about? Any help would be appreciated.

06-15-13, 11:57 AM
Its pretty straight forward. I had to dig out my socket till I learned that taping the socket to the extension was a much better solution. I use petroleum jelly on the electrical connections and rubber to keep moisture out. Good luck!

06-15-13, 01:15 PM
So, looking at the plugs (denso iridium) I see they are 0.4mm and in the manual it say "spark plug gap 1.1mm". Do I gap the densos to their specs or to what my manual says?

06-15-13, 02:18 PM
My opinion, but I would set the gap to what the engine calls for. Personally I would not waste money on after market plugs, just used the OEM. The biggest problem is oil getting on the plugs. Invest your money on an oil catch can. Again my opinion.

Good luck

06-15-13, 02:27 PM
You're the third person to mention a catch can. Sounds like a sound investment. An I'm assuming I'm putting that on the dirty side? Is his all due to the direct injection?

06-16-13, 06:49 AM
From what I understand and again my opinion; these engines have a tendency to use oil. I've owned GM vehicles primarily throughout my driving years and GM engines use oil. It can be from valve guides, piston rings or both. Its not a problem typically because many engines use oil unless it becomes excessive. The direct injection doesn't come in to play on this problem. The engine basically sucks the blow by (oil fumes) into the cylinders and burns it. The catch can intercepts these little droplets and prevents the spark plugs from getting fouled. Spark plugs in a clean burning engine will last many many years. The coil packs are a different problem and should be proven out also. There are great threads on all of this info..dig around a little and good luck.

06-16-13, 11:12 AM
Really easy. Take the time to remove the strut bar. The 5 mins it takes to remove it will save you 15 mins in making the whole process faster. Also my old plugs had no signs of oil on them but were worn enough to require replacement after 75k mi. I thought my car burned oil. But turns out it doesn't or uses very little.

06-16-13, 10:58 PM
follow up..... Plug change went well. It was ridiculously easy with the narrow plenum. I do have a final question though. The reason why I had to change the plugs was because I had a bad coil, which I replaced, and was advised that since I changed one of the spark plugs during the coil change, I should change them all. I didnt have the money to do it right then. I still had misfires once the coil was changed. 2 weeks later (today), I changed all 6 plugs. The 5 original ones had normal burnout on them and no oil. Looked like normal wear. When I took out the plug that had only been there 2 weeks (from the coil change), there was a LOT of carbon deposit on the neck of the portal (no oil though). Should I be concerned? I was told that it may be from the misfiring that was happening during the 2 weeks that was shooting fuel in there with no spark to burn it off. Anyone know anything about this? Is there anything I need to do (other than a TB cleaning possibly but I wanted to do that anyway)?

06-21-13, 07:08 PM
I have a flag up on this. If it where mine I would swap the coil and the plug with another cylinder run it for two weeks and check it again. As a troubleshooter I would want to prove out the coil plug and cylinder. If the questionable cylinder dirties up again I would next try a cleaning product. It could be nothing but I would also do a compression test on all the cylinders. Do a smoke test with a friend. Have a friend drive your car and you follow. Get the vehicles up to a good speed and let off on the gas and let it coast for about 15 seconds then accelerate. If you observe a good puff of smoke out of the tailpipes it could be a little more serious. I would also still invest in the oil catch can. So far this is inexpensive and could be normal. Best of luck!