revolcallidac Posted March 2, 2012 Report Share Posted March 2, 2012 Well, my first problem. Let me say my car is still under warranty for 23,000 more miles.. an 07 DTS NHP...but...the dealership had it for a week and even though the service manager himself felt the car missing AND it had a trouble code stored in it AND I told them what my code reader said "misfire cylinder 6" they CLAIM they can't pinpoint the problem. They say the plugs "looked ok". It only does it on cold start and most noticeably on cold or damp days. I'm thinking it's either a plug or coil. When it gets warm it smooths out, maybe an occasional stumble but for the most part smooth as silk. Also, it's only at idle, especially when in R or D and sitting stopped at a traffic light or something, almost like a manual shifting car trying to buck. Mash the gas just a little to get RPM's up to just above idle speed and it's completely smooth again. I've tried different gas, tried fuel injector cleaner, lucas, sea foam just to see but still there. I have until July 5 for GM to find it and fix it under warranty. Am I completely out of the ballpark or does it sound like a plug or coil to y'all? Sometimes dealerships need a little help. If it weren't a warranty issue I'd just change all 8 plugs since thats the cheapest thing to do first and go from there. I might just change plug #6 and see what happens. Link to comment Share on other sites More sharing options...
Texas Jim Posted March 2, 2012 Report Share Posted March 2, 2012 Just off the top of my head it sounds like a coil... I think I would just replace the #6 plug with the correct AC DELCO plug, and see what happens. If it still has the misfire, maybe try taking it to a different dealer. Sounds like your dealer don't really want to fix it or he would have changed the plug and if that didn't help, he would have changed the coil. As you probably know... that engine has coil on plug ignition... Link to comment Share on other sites More sharing options...
revolcallidac Posted March 2, 2012 Author Report Share Posted March 2, 2012 My thoughts too...they even said they looked at ALL the plugs! That's half the cost right there. At least they gave me a 2011 CTS to tinker around in while mine was in for "service". Thanks for the input. Link to comment Share on other sites More sharing options...
Texas Jim Posted March 2, 2012 Report Share Posted March 2, 2012 My thoughts too...they even said they looked at ALL the plugs! That's half the cost right there. At least they gave me a 2011 CTS to tinker around in while mine was in for "service". Thanks for the input. If I am not mistaken... the dealer may have screwed up just a little... The plugs have a special anti seize coating on them. They are designed for "ONE TIME" use... once taken out of the car, the coating is no good anymore. If they are reinstalled and left for a long time... you may never get them out of the head without stripping the threads inside the head where the plug screws in. Link to comment Share on other sites More sharing options...
KHE Posted March 2, 2012 Report Share Posted March 2, 2012 Not sure where the "one time use only" originates for the plugs. The plugs do not have anti-sieze on the threads - they have a plating which prevents them from becoming stuck in the head. I would take the car to a different dealer as the one you're dealing with sounds like they don't know which way to turn a wrench..... They should be able to identify the missing cylinder with a Tech-2 and there are only two components that would cause a misfire - the coil bank assembly or the plug itself. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
Logan Posted March 2, 2012 Report Share Posted March 2, 2012 That version of Northstar does have a misfire code for each cylinder. So there is a code for each cylinder...po301 thru po308. Also, I'm pretty sure each coil can be replaced. You do not have to replace the entire coil bank like earlier cars. Logan Diagnostic LLC www.airbagcrash.com www.ledfix.com www.ledfix.com/yukontaillightrepair.html www.ledfix.com/ledreplacements.html www.ledfix.com/j42385toolrental.html Link to comment Share on other sites More sharing options...
Paul S Posted March 2, 2012 Report Share Posted March 2, 2012 Could it be the beginnings of a blown head gasket? Link to comment Share on other sites More sharing options...
KHE Posted March 2, 2012 Report Share Posted March 2, 2012 Could it be the beginnings of a blown head gasket? Highly unlikely. 2004+ Northstars have a much improved head bolt design (longer bolts, coarse pitch which equals more retention in the block). Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
Cadillac Jim Posted March 4, 2012 Report Share Posted March 4, 2012 Most blown gaskets start with the corner cylinders, and #6 is in the middle. Rock Auto lists the coils at $59 each for this car. The loaner costs them more than that for more than two days. I think KHE has them cold - you are dealing with Mr. WhutWrench. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
revolcallidac Posted March 5, 2012 Author Report Share Posted March 5, 2012 I think I'm inclined to agree with you. Went out today, mind you it's almost 60F here, started the car with remote start...waited a few minutes in the house to finish what I was doing and went to get in the car...it was not running. I just thought I'd taken longer than I meant to and it had shut off...but it was cold inside. Started it and immediately noticed the misfire...worse than previously...and it had tripped the CEL again which is probably why the car was cold, it shut itself off. It won't start remotely with the CEL on P0306 cylinder 6 misfire detected...and I smell gas fumes pretty strong. When it gets to operating temperature it goes away. When the dealer had it a month ago the CEL turned itself off after a few trouble free starts...Oh well, I guess I'll have another CTS or even an Escalade to ride around in for a few days...I'm listed as a VIP customer so I always get another Cadillac. At least my commuter car can't have this problem...it doesn't even have spark plugs or coils...TDI Thanks, I just may have to drive 35 miles to the next dealership...at least it's still under warranty...if it should turn out to be a head gasket issue they HAVE to fix it under warranty. Link to comment Share on other sites More sharing options...
revolcallidac Posted March 7, 2012 Author Report Share Posted March 7, 2012 Well I decided to see if I was smarter than my dealership and splurged on a $7 AC-Delco spark plug, just one to see what would happen. Changed it in 15 minutes yesterday, then upon first startup of today at 32F, amazingly I had NO Misfire!!! How difficult would this have been at the dealership with the plug already out to be "looked at"? It was worth the $7 to not have to deal with the hassle of going over there, getting the runaround, and still not having my car fixed. I ought to send the receipt to the dealership and see if they will reimburse me for it Thanks for your input. Link to comment Share on other sites More sharing options...
Texas Jim Posted March 7, 2012 Report Share Posted March 7, 2012 Well I decided to see if I was smarter than my dealership and splurged on a $7 AC-Delco spark plug, just one to see what would happen. Changed it in 15 minutes yesterday, then upon first startup of today at 32F, amazingly I had NO Misfire!!! How difficult would this have been at the dealership with the plug already out to be "looked at"? It was worth the $7 to not have to deal with the hassle of going over there, getting the runaround, and still not having my car fixed. I ought to send the receipt to the dealership and see if they will reimburse me for it Thanks for your input. Glad it is fixed and thank you for reporting back on the solution. :) Link to comment Share on other sites More sharing options...
hjb981 Posted March 10, 2012 Report Share Posted March 10, 2012 Just a thought on what might have have happened: the insulation in a plug can crack, causing them to malfunction. This is not necessarily obvious upon visual inspection (it can be seen if the plug is fired out in the open - the spark usually ends up in the wrong place (not between the electrode tips) if it happens). Link to comment Share on other sites More sharing options...
revolcallidac Posted April 7, 2012 Author Report Share Posted April 7, 2012 Just an update.....I later went ahead and changed the remaining 7 spark plugs and I could really tell a difference in the way the car runs. But...a couple weeks later the misfire showed up again, same code, same cylinder...so I ordered a new coil which arrived yesterday and I changed it out this morning. It was a cold morning, 40 degrees, first start of the day with the new coil....no more miss. So I guess it was a bit of a combination of needing plugs and one bad coil pack. My dealer has offered to give me a free Mobil 1 oil change for my trouble that they did NOT diagnose nor fix. That will cover the cost of the new coil. These cars are pretty persnickety...that misfire was causing the stabilitrak to give warning messages as well as the check engine light...dealer says they are tied together. Link to comment Share on other sites More sharing options...
Texas Jim Posted April 7, 2012 Report Share Posted April 7, 2012 Just an update.....I later went ahead and changed the remaining 7 spark plugs and I could really tell a difference in the way the car runs. But...a couple weeks later the misfire showed up again, same code, same cylinder...so I ordered a new coil which arrived yesterday and I changed it out this morning. It was a cold morning, 40 degrees, first start of the day with the new coil....no more miss. So I guess it was a bit of a combination of needing plugs and one bad coil pack. My dealer has offered to give me a free Mobil 1 oil change for my trouble that they did NOT diagnose nor fix. That will cover the cost of the new coil. These cars are pretty persnickety...that misfire was causing the stabilitrak to give warning messages as well as the check engine light...dealer says they are tied together. Glad you got it fixed. A free oil change is always good... :) Maybe I need to change my plugs if it makes a lot of difference in the way it runs. Mine has 113,000 miles and I am still on the original plugs. Oh... by the way... see my post #2 that is right after your first post.... :D Link to comment Share on other sites More sharing options...
JohnnyG Posted April 7, 2012 Report Share Posted April 7, 2012 Caddy dealerships today seem to need help alright! Some of them a LOT of help. I fouled a plug on my 2008 DTS last fall, it was on a cold, damp, and rainy evening, after a short trip to a local resturant. In that situation I had also used the remote start feature to get the car warmed up a little. It seems to me that the remote start feature is at a disadvantage in these situations because it cannot rev up the engine (a little) just after such a start. It also seems that if there are any "weak links" in the ignition system, the dampness combined with the remote start will reveal them immediately. At least my dealership changed the plug right away under warranty. Never underestimate the amount of a persons greed. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.