I have a 2004 Trailblazer with the 4.2. CEL lit up, P0300, multiple misfires. Changed plugs, the plugs that came are AC/ Delco 41-981 with 12569190. Is it possible these are the original factory installed spark plugs? Just bought this truck 2 years ago from a private seller, so I'm unsure about maintenance history.

 

Welcome from Florida. I think the mileage you typed in is wrong. I am guessing you mean 125,691. If this is true then yes it is possible those might be the original plugs. The only I found is that 41-103 should be the correct plug, so I don't know for sure.

 

I think you misunderstood my original post. 12569190 is printed on the porcelain part of the spark plug along with 41-981. I'm thinking the long number is a GM part number

 

According to my Owner's Manual for our 2004 TrailBlazer, the GM part number for the ACDelco 41-981 plug is 25337472, However when I look your number up on a GM parts website, your number shows that it has been superseded by 5 other part numbers, one of which is the number from my Owner's Manual. So, in short, I would say that your plugs have been in there since the vehicle left the factory.

I hope you installed only ACDelco 41-103 spark plugs (the factory recommended replacement for the 41-186 plug. These engines are picky in what plugs go in them so please use nothing other then the ACDelco 41-103. Additionally, stay away from purchasing them from Amazon or ebay due to the prevalence of counterfeit ACDelco spark plugs on those two websites. If you want to save a few dollars, purchase them from rockauto.com because they use factory authorized distributors/warehouses to fulfill their orders.

Good Luck!

 

The AC-Delco 41-103 are iridium plugs but you cant go wrong with those.

 

Yes The Original AC Delco 41-981 Platinum Plugs Were Discontinued And Replaced With AC Delco 41-103 Iridium Plugs . I just went through this on my 2004 GMC Envoy cuz 1 plug was hard to get to had the original 41-981 for 160,000 miles lazy mechanics did not change it at 80-100k miles cuz it was hard to get to smh hope this helps