Changing Spark plugs and Spark plug wires (Tuneup)

[Bruce Nunnally]

My 92 STS 4.9L had/required double platinum plugs, so I would not be surprised if the 91 did as well.

The plugs are not impossible to replace on the 4.9L, but you will want to do it with the engine cold, since you have to lie across the engine and do the back bank by feel. A spark plug wrench with an articulated head helps. Be careful, as there is a sensor between the two plugs on the back bank -- on the driver's side -- so don't take it off which wrenching on of those plugs.

I have heard that at the dealer what they do is disconnect the front engine mounts and roll the 4.9L engine forward to access the rear plugs more easily.

Try gmotors.com, gmpartsdirect.com, or parts.com for discount new AC/Delco wires and plugs.

[Ralph]

Thanks for the tips guys. No the plugs were never done (low mileage) but I will eventually. I think you are right Kat, I don't think they are platinum because #1 the change interval recommended is 50,000kms and #2 there is no "P" prefix in the part number for the plugs. (a friend mentioned this to me and maybe you guys know if it is true). As for the plugs along the firewall bank, yeah, I used to have to sit on my Pontiac air cleaner and do them by feel, not as bad though 'cause there were only three there. Bloody knuckles afterwards.

[Ralph]

Originally posted by Bruce Nunnally
My 92 STS 4.9L had/required double platinum plugs, so I would not be surprised if the 91 did as well.

The plugs are not impossible to replace on the 4.9L, but you will want to do it with the engine cold, since you have to lie across the engine and do the back bank by feel. A spark plug wrench with an articulated head helps. Be careful, as there is a sensor between the two plugs on the back bank -- on the driver's side -- so don't take it off which wrenching on of those plugs.

I have heard that at the dealer what they do is disconnect the front engine mounts and roll the 4.9L engine forward to access the rear plugs more easily.

Try gmotors.com, gmpartsdirect.com, or parts.com for discount new AC/Delco wires and plugs.

Yeah the dealer disconnects the engine mounts and rolls it probably just to get more labour out of suckers like me!

[Katshot]

The plugs don't have a "P" prefix. I believe the AC plugs use a "41" series (prefix) which designates them as Platinum.

[Ralph]

Originally posted by Katshot
The plugs don't have a "P" prefix. I believe the AC plugs use a "41" series (prefix) which designates them as Platinum.

Damn, I don't have the "41" series prefix. Man, looking at the far bank, I have no idea how I will change the plugs. One can hardly get a slip of paper through there let alone my hand! I guess some things are best left to the experts (mechanic). Newer cars recommend 166,000 miles before a tune-up, but I would never let it go that long for my own personal vehicles. I think that number is a bit on the high side for people that like to neglect their cars, etc. After my pcv valve froze up on my Merc. and cost me 1200 in new oil seals, I like to stay on top of things, but I cannot find the pcv on the 4.9!!

[Katshot]

That's not 166,000 miles, it's KILOMETERS. And the the easiest way to get to the plugs is to slide you arm up from the back of the motor (driver's side of the car). I usually lay on top of the engine and slide my arm up between the engine and cowl from back of engine towards the front. There's actually plenty of room.
Also, remember that even though the OEM only recommends changing the plugs at that mileage, I would also do the wires.

[Ralph]

Oh yeah, kilometers, damn I hate the metric system.

[Stoneage_Caddy]

ahh thanks guys i was just gonna ask the same question , trying to resolve a pinging issue on my 94 with 111,114 miles on it (running 93 octaine)