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Ignition miss 2004 Deville


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My wife's 2004 Deville has developed a severe ignition miss.  PCM P0300 code and flashing check engine light when the car is driven.  With the car idling, I unplugged the injectors one at a time looking for one that did not cause the engine to miss worse but couldn't really tell.  Using a stethoscope, I could hear each injector working so I decided to pull the coils and check for spark.

The front bank was easy - spark on all four coils.  The rear was a PITA - whoever decided on the mounting of the secondary air pump cutoff on the cam cover with all the bolts hidden has never had to remove one of those... Once I had that out of the way, I tested for spark and #3 was not sparking.  I moved the coil to #5 and retested, still no spark.  I checked it once more and it began sparking again so I think there is a thermal open on that coil.

GM changed something so individual coils can't be purchased unless they are the latest design which these are not.  I know there was an issue with the 2000-2003 coil cassettes and wonder if there is a similar issue here.  I am tempted to pull the coil module from my 2005 and swap it in there but am nervous about that - seems like it is too easy to then have two cars that have problems.

Anyone have any experience with the 2004-2005 ignition system?

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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I re-tested for spark this evening - the #3 coil is definitely flakey.  It was not sparking, then it would spark some of the time.  I ordered a new coil on rockauto.com.  I'll save the three good coils to swap out any future bad ones on the left (front) bank if they ever go bad.

I thought about swapping one of the coils from the front to the back in order to be able to reinstall the secondary air injection pump cutoff, then when the new coil module arrived, I could easily install it on the front bank in about 5 minutes but... that air pump cutoff mounted on the rear cam cover is such a royal SOB to remove so I want the newest coils on that bank.

I purchased this car in January and am still going through it - the car is in very nice condition and didn't require much but this issue caught me by surprise.  Someone replaced the spark plugs prior to me purchasing it.  They were very tight in the heads.  I was worried I'd ruin the threads in he heads while removing them.  There were two missing bolts as well - one for the coil module mounting and one on the secondary air injection cutoff.  I guess it is too much trouble for hack mechanics to do the job properly.  I purchased new bolts to replace the missing ones.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Probably because that AIR injection check valve that is in the way and a PITA to remove...LOL.  That wasn't on the previous generation Northstar engine - maybe it was mounted in a different location? 

I finished the job yesterday evening.  It is back to normal and now I have three spare coils now in case any of the front coils go bad.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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