Spark Plugs For A Canadian Denali

[Rocket Man]

After buying my '02 Denali a couple years ago, I found out it was a Canadian model. The HVAC controls in Celsius was a giveaway (which I changed to US versions), as well as the RPO code of Z49 (Export Canadian Modif Mandatory Base Equip). So I'm getting ready to change spark plugs and the owner's manual says to use NGK PZTR5A15 (7862) which are listed as Laser Cut Platinum, with a gap of .060. Everything I can find here on this site point to other plugs for the LQ4, as do the GM dealer parts sites. If I start to order the 7862's, every parts site say they don't work for the LQ4 '02 Denali. Also, every post here as well as the parts sites state to use a .040 gap. Is there anyone else out there with a Canadian Denali who has run into this ? I guess I'll order the plugs specified in the owner's manual and gap them at .060 but I'm wondering what would happen if I took it to a shop and they put in the US plugs at .040 gap- probably be fine huh? Just curious, wondering why Canada would be different. I know that Cali has different smog requirements but never heard they use different plugs.

 

[Rocket Man]

Well I went to NGK Canada and they list the Iridium IX TR51X (7397) as the longest-lasting for the LQ4 '02 Denali so I ordered them. I saw those listed somewhere else here on the forum as a recommended plug. They also show as compatible for my truck on the parts sites.

 

[Rocket Man]

Now I'm questioning what I should gap them to. My owner's manual says my gap is .060, but that's for the 7862 Laser Platinum's. I assume I should still gap the plugs at that even though they're Iridium IX. NGK says these "fine wire" plugs should be gapped to mfr. specs , just don't touch the electrode when doing so. Has anybody else gapped their plugs to .060? I've never ran into this problem before! I don't want to ruin these plugs. Help!

 

[TheAutumnWind]

Now I'm questioning what I should gap them to. My owner's manual says my gap is .060, but that's for the 7862 Laser Platinum's. I assume I should still gap the plugs at that even though they're Iridium IX. NGK says these "fine wire" plugs should be gapped to mfr. specs , just don't touch the electrode when doing so. Has anybody else gapped their plugs to .060? I've never ran into this problem before! I don't want to ruin these plugs. Help!

Well, all the lq4's originally called for .060 gap, and the mfr changed the recommended gap a few years later.

You can set the gap with pliers without touching the electrode, but dont use anything that makes contact with the electrode.

I'd see how it runs @ .040. Most likely fine. I doubt there is any noticable change running them @ .060, you'll likely lose a tiny bit of life since the gap increases with wear (most likely why GM decided to change to .040 so that they could claim they were good for 100k mi or something) but you might find a few extra hp opening it up a bit.

Personally I just picked up the cheaper variants and gapped them a bit larger. I'm fine with replacing them more often ( and I only spent like $20 IIRC)

 

[Rocket Man]

I found this after my last post and while it's OK to change the gap on an Iridium plug as you stated, Chris, I just checked and found only 2 that weren't quite .040. I gapped those 2 per NGK's instructions for these plugs, without touching the electrodes. Back in the days, people were damaging the plugs because they were gapping the old way by prying on the electrode. BTW, NGK only claims 50 k mileage wise for these. The update from GM:

Subject: Information on New Spark Plugs and Gapping #03-06-04-060 - (10/24/2003)



Models: 2004 Buick Ranier

2002-2004 Cadillac Escalade, Escalade EXT

2003-2004 Cadillac Escalade ESV

2004 Cadillac CTS-V

1997-2004 Chevrolet Corvette

1998-2002 Chevrolet Camaro

1999-2004 Chevrolet Silverado

2000-2004 Chevrolet Suburban, Tahoe

2002-2004 Chevrolet Avalanche

2003-2004 Chevrolet Express, TrailBlazer

1999-2004 GMC Sierra

2000-2004 GMC Yukon, Yukon XL

2001-2004 GMC Yukon Denali, Yukon XL Denali

2002-2004 GMC Sierra Denali

2003-2004 GMC Envoy XL

1998-2002 Pontiac Firebird

2004 Pontiac GTO

2003-2004 Hummer H2

with 4.8L, 5.3L, 5.7L or 6.0L V-8 Engine (VINs V, P, T, Z, G, S, N, U -- RPOs LR4, LM4, LM7, L59, LS1, LS6, LQ9, LQ4)




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A new spark plug has been released for use in the above vehicles. The new spark plug has an Iridium tip instead of the current Platinum tip. Due to the different tip design, the gap of the spark plug has also changed. The new spark plug, P/N 12571164 with AC Delco P/N 41-985, is gapped to 1.01mm (0.040 inches) when the spark plug is made. The spark plug gap is set during manufacturing and should not be changed or damage to the spark plug may result. Any new spark plug found to not be properly gapped should not be used.

 

[TheAutumnWind]

I found this after my last post and while it's OK to change the gap on an Iridium plug as you stated, Chris, I just checked and found only 2 that weren't quite .040. I gapped those 2 per NGK's instructions for these plugs, without touching the electrodes. Back in the days, people were damaging the plugs because they were gapping the old way by prying on the electrode. BTW, NGK only claims 50 k mileage wise for these. The update from GM:

Yeah I can't believe that auto parts stores still sell these to people with new plugs! I remember beating on my copper plugs back in the day. Still have one of these relics without the "gap opener" hole.

 

[SLCHOE]

Yeah I can't believe that auto parts stores still sell these to people with new plugs! I remember beating on my copper plugs back in the day. Still have one of these relics without the "gap opener" hole.

They work fine with copper electrode plugs. The fail is the parts counter guys who sell a customer a set of platinum or iridium plugs and then SUGGEST THAT TOOL and a packet of anti-sieze (nothing wrong on the anti-sieze). They don't know any better so BYOB (Bring Your Own Brain).

 

[Rocket Man]

Installed the Iridium IX NGK's with gap at .040 today along with MSD Superconductor wires. I swear the old plugs looked like originals! At 140 k they might be. They are the ones called for in my owners manual and their gap was about .070 which would be normal for old plugs that started life at .060. And now my motor screams. Big difference; I think the BB tune really works now. Unbelievable how quick I can go from 60 to 90 on the freeway after this.

 

[gtptyler]

I too have a 02 Canadian Denali, I never paid attention to my owners manual when I changed mine

 

[TheAutumnWind]

Installed the Iridium IX NGK's with gap at .040 today along with MSD Superconductor wires. I swear the old plugs looked like originals! At 140 k they might be. They are the ones called for in my owners manual and their gap was about .070 which would be normal for old plugs that started life at .060. And now my motor screams. Big difference; I think the BB tune really works now. Unbelievable how quick I can go from 60 to 90 on the freeway after this. View attachment 59626

Those were certainly ready to be replaced.