I own a 2001 Seville which has 130K miles on it. I have had the car about two years. It is running okay but I have no way of knowing how long it has been since the spark plugs were replaced. Should I simply wait untill the engine starts misfiring or should I go ahead and replace the plugs, now? If so, what kind of plugs are recommended and how do I go about doing this, myself. I consider myself pretty competent in engine know-how - however, I have never worked on a Northstar V-8 before.

 

i have a 99 sts and mine starting misfiring at around that millage. I changed the plugs and wires as i knew they were original. You can tell the original wires by each wire being numbered to the cylinder it goes to(nice idea). Even if you buy replacment wires from GM they no longer have the numbers to cylinder on wire. so i did both plugs/wires on mine and was pretty sure plugs were original as i got the car with 98K and it had about 3owners before, so i figured each one of them didnt have it long enough to change that stuff. youll have to remove the coil pack on the rear bank of plugs. If remember there are four 10mm bolts holding it down 2 rear are not visible you have to do it by feel, jus dont drop them. ITs pretty basic from there. I used ac-delco plugs and wires, that should get you another 100K. Plugs gap at .50 I got my parts cheapest at gmpartsdirect.com

 

Thanks 99STSGUY. I bought AC-Delco replacement plugs today and the job is now complete. Took it out for a test drive a while ago and it runs fine. It was pretty much like you said - the rear bank was definitely the challenge. Don't think I'd like to do that, often.

The old plugs were by Denso which according to the parts guy were NOT original equipment on my car. So I guess that means the plugs had been changed at least once before.

 

You bet anytime, happy to hear all is well!

 

just wondered if ya did wires also?
rickyd

 

No - my engine has a big metal thingy on each bank that contains the wires, internally. You simply remove 8 10mm studs that hold this down and the whole thing just lifts off. Removing 4 of the eight studs on the rear bank are the real challenge to this job. They are very difficult to gain access to.

 

Oh thats right they went to coil on plug for 2000-up. to do away with wires, so unless a coil was bad theres not much to maintain i believe.

 

I just changed the plugs in my 01 as well. I also believed that they were original.
I also removed Densos
I dont know where your from, but Im in Canada. And I wonder what the odds are that we both had Densos. Specially seein as Ive never even heard of them here before.
Im guessing that they are original.