Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Denali spark plugs

Is it difficult to change the spark plugs on a 2007 GMC Denali with a 6.2 liter V8.

Not really.

Just remove the plug wire without damaging it, and use the proper socket, extension, and U-joint to remove and install the plugs.


@Groy I would also budget for a spark plug wire set and the spark plug heat shields. We have tons of GMC trucks in our fleet, and the plug wires and heat shields often don’t survive, so we replace with new

I recommend AC Delco, for all of the parts

I’ll give you some advice, to save your back. Put the front of the truck on jackstands. Remove the tires and the fender liners. Work through the fender well. It’s much gentler on your back, versus leaning over the fender


Are not these coil on plug? They can be very sensitive to improper care.

@Barkydog Yes and no . . . each cylinder has its own coil, which is sitting on the valve cover

This engine does not have hemi heads, I believe

The plugs are on the side of the head, just above the exhaust manifold

Each plug is connected to its coil, by a short ignition wire

I’m not sure what you’re referring to by “improper care” . . . ?

What this engine has is referred to as “coil near plug”

The coils do not need to be removed for a tuneup. I’m not sure if that’s what you were getting at, though


They’re coil near plug.

The coils are mounted on the valve cover, and each coil has a short spark plug wire to the spark plug.


@db4960 Improper care refers to sensitive wires possibly graphite that are sensitive to extreme bends or pressure when removing, Kind of like fiber optic network connections.

@db4690 Thanks for clarifying

I’ll say this . . . sometimes, on this particular engine, even if you are extremely careful and use the proper tools, the wires and heat shields still take a hit when you’re removing them

Best to have a fresh set on hand

I have a 2008 GMC Sierra 1500 Denali 6.2L.
Time to change the spark plugs & wires…

What socket and extensions do you recommend to reach the back plugs? Any particular trick to reaching those?

It looks like the driver side plugs are pretty easily accessed. The Passenger side looks like the back 2 might be really hard to reach.

Any tips are welcome.

Well I didn’t get any responses but I went ahead and did my plugs. It was actually pretty easy, including #8, and I did NOT have to go through the wheel well to do it. This was my approach:

  1. Use a ~15" high step platform (available where ladders are sold) alongside truck to gain easy access bending over engine. This is a huge help to access all plugs.And one of the handiest home “tools” I own for other things like painting, staining elevated fences, etc. About $35 at home depot, etc.
  2. I used a fender protector to protect my paint from any scratching. $15 on amazon…worked fine.
  3. Used a GearWrench 80546 5/8-Inch x 6-Inch Swivel Spark Plug Socket (available on amazon or at my local Car Quest Autoparts for $10) for plugs 1-7 with a ratchet that also had a swivel head. a normal ratchet wrench would have worked fine too. You could use a magnetic plug socket without the extension, plus an extension or a universal & extension. But this thing was pretty great. That magnetic spark plug socket with the swivel is a huge improvement over the old rubber grommet style sockets. Plugs 1-7 were quite easy to access and change. On the passenger side, pull the two hoses out of their clamp to move them around as needed for access. Otherwise, I didn’t move or remove anything else at all.

Plug #8: I used a magnetic spark plug socket with NO extension ($7 at my O’Reilly Autoparts) , and a craftsman 3/8" ratchet wrench, of the smaller, shorter variety. I also used a 3/4" regular socket on the back of the sparkplug socket to slightly extend it’s length. The spark plug socket was 2-1/2" long. With the additional socket on the back, the combined length was 3". That was PERFECT for clearing the manifold but maximizing space between the plug and the heat shield that is about 3-4" directly out from the plug. This was perfect for breaking the plug loose, and for tightening it. With the engine completely cold I was able to reach under the hoses and along the block with my right arm, and/or straight down from above #8 with my left arm to perform the needed steps. Standing on the platform by the truck is essential to being able to reach this stuff. But with that, it was easy and fast. I supported myself along the back edge of the engine compartment with my left arm when reaching with my right, or on the alternator with my right hand when reaching with my left. I did use some long nose pliers to pull the old boot off the plug - I was able to pry against the exhaust manifold to get it loose. I couldn’t pull that one off by hand due to the small clearance space to get any leverage. I finger loosened and finger tightened the plug other than the initial “breaking loose” and final “tightening down”. All told, it took maybe 10 to 15 minutes to do plug #8, and I was taking my time. Of course, use anti-seize on the plug threads and silicone gel on the spark plug boot/top of plug.

My plastic wiring conduit (black plastic 3/8" “hose” covering wires") was crumbling to the touch, so I picked more up at autozone for $6 and redid that after the plug change.

I thought this was going to be a pain to get to the two back plugs on the passenger side but it was actually easy. Now that I’ve done it on this engine, and know exactly what tools to use where, I could do this job again in under 30 minutes if I was trying. Maybe under 20. The dealers who wanted $485 at $625 in my area should be ashamed…that is just robbery. The parts cost me $100, for OEM AC Delco plugs and wires on Amazon.

+1 to that suggestion!

I’ve also done it pretty much the way @KenG18 mentioned

And it’s not kind on the body

I stand by my earlier recommendation . . . put the truck on jack stands, remove the tire and inner fender liner

I can’t speak for anybody else, but I’ve got a bad back . . . scoliosis . . . so the way Ken did it isn’t a good option for me

As for his claims of robbery . . . he’s comparing apples to oranges, in my opinion. And I suspect he may not understand how shops come up with their estimates, and what it costs to keep a business afloat

I have said this before . People complain about repair prices for almost everything. Vehicle , electrical , plumbing and other services. Why can’t they realize the expenses of a facility plus insurance and giving the employees a living wage . Not to even mention the cost of equipment some of which might not be used on a daily basis.

With all due respect to the prior posters:

If going through the wheel well worked for you, great. I’m happy for you. It seems that would have added a lot of time, required additional tools, been riskier and been harder on the body than the way I did it, at least on my specific vehicle. Still if it worked for you, that’s great. But I will point out that:

  1. I have a bad back too (football injury) and there was not any strain on any part of my body at any time. I’m 6’ and 240 and I have bad knees too and working at ground level through a wheel well is a lot harder than just reaching comfortably into the engine compartment, leaning on one arm or the other for a couple minutes. You may have overlooked the platform to stand on. That makes all the difference. If you were trying to lean over the fender from the ground or crawl up on the body or the engine…forget it…yes that would be hard on YOUR body, hard on the TRUCK BODY, and foolish.

  2. I have nothing against dealers or non-dealer shops and I do almost all of my work at dealers and occasionally use smaller shops for certain specific tasks. I hardly ever work on my car myself anymore because frankly, I really just don’t have to. But I’m sorry. Charging $625 to put in spark plugs and wires…parts that cost the shop less than $75 (probably $50) and would take them 30 minutes or less to install…that’s pretty outrageous in my book, especially when I was doing another $1200 worth of highly profitable “100K Maintenance” work in the shop at that same time they quoted that. I also did not pay them $140 to put on a trim piece I bought for $40 online and put on in less than 5 minutes, or a mirror they wanted $500 to install that took all of 20 minutes and cost me $200 for the same OEM part. So they got a lot of work and profit, but they could have had more if they were not such greedy pigs.

  3. I have plenty of knowledge of what it takes to keep a business afloat, as well as an MBA and an engineering degree. I have respect for businesses, and I’ve run some of my own as well as handled many millions of dollars of financial planning in large corporations. But I expect the businesses to have respect for me as a customer too. I work hard for my money too. So cry me a river. Charging $1500/hr in gross profit margan to change spark plugs is not respectful of me as a customer. This is a job anyone with a ratchet wrench, a $7 magnetic socket, and a platform can do in less than an hour and a shop who does this job every day could do it in 20 minutes on this vehicle. That’s not profiting, it’s profiteering. It’s gouging.

  4. Jacking the vehicle and working under it presents additional serious risks to the amatuer mechanic that a shop with a hydraulic lift does not face, due to both the quality of tools a lot of them will buy and the lack of a work area that is actually flat and level. It can be done safely with the right tools, but those tools cost hundreds more than you need to spend to do THIS JOB on THIS VEHICLE. It’s fine if you already have those tools, or plan to use them for other jobs too. But it seems to me that for this vehicle, going through the wheel well is riskier, more expensive, more time consuming, and totally unneccesary. But if it worked for you. Bravo.

  5. I suspect the people recommending going through the wheel well are trying to discourage people from doing this job themselves. Possibly mechanics or shop owners, I don’t know. I notice there was not a single reply for a week when I asked for tips for my specific vehicle, but as soon as I detailed how easy it was to do with the right very inexpensive tools and gave a detailed description…I have two replies in just a few hours. Odd? Seems like it to me.

Did you miss the part where I said I had scoliosis?

I’m a professional mechanic

And doing it the way you described it is worse for me . . . I’ve also done it that way, on occasion

My knees aren’t that great, either . . . I use foam pads to kneel on

We have tons of trucks just like yours in our fleet, and I’ve seen very few guys do plugs in 30 minutes or less

Working at that speed WILL destroy your body over time

I’m not saying mechanics should be lazy, but they also shouldn’t be expect to work in a manner that will “use up” their body in a few short years . . . they need it to put food on the table

I’ve seen a lot of guys that were so “motivated” that they didn’t work safely. They worked so fast and so recklessly, for a few years. And then they were permanently injured and couldn’t even do the job at all. And they had nobody to blame but themselves. If you burn the brightest, you’ll probably burn out the quickest. Not exactly the way to ensure you’ll be able to continue plying your trade for a few decades

So you didn’t get a response to your initial response . . . don’t take it personally. There is a lot going on as far as this forum goes. Not everybody gets the answer they want, some people don’t even get a response.

A decent jack and jack stands don’t cost the world. You don’t have to buy an otc, hein werner, or something like that. But decent sears jack and jack stands will do just fine for diy use. As for tools, sears is pretty much giving away their tools nowadays. And there’s always ebay . . . lots of deals to be found there, as well.

Are you aware that shops are expected to mark up their parts. What you paid for parts is irrelevant. If shops don’t make a fair profit on their parts and labor, they’ll soon be out of business. And then you won’t have anybody to go to, when you do need them . . . shops aren’t going to charge you only $50 for the parts

I’m not trying to discourage you from doing your own work . . . in fact, I gave you a few pointers

I am not a mechanic but I have done this job on my son in laws 2007 Chevy pickup. I am a little bigger than you and quite old. I also have a bad back and knees and the twisting force that would be generated by my holding my weight with one hand while working with my other would have put me in bed or flat on the floor for a week.

Doing it from underneath is much easier for me.

How long a job take me is not much of a concern for me. I am not under the time pressure of making a living. So when I finish, there are no wires too close to the manifold or rubbing the heat shield, broken plastic clips etc like I find when I pay someone else (even dealers) to do things for me.

I actually enjoy working on cars these days unlike my younger days when I would come home after a 10-15 hour day and work all night on the car so it would be fixed in the morning so I could go to work.

Left to readers to decide how best to proceed in their situation.

My comments are for the DIYer who needs to do this task once every 100,000 miles, on this specific engine, in this specific vehicle.

I think my method is the fastest, cheapest, SAFEST, uses the most basic and readily available, inexpensive tools, and is overall the most practical for a typical DIYer. I have a bad back and bad knees and my approach could not have resulted in a simpler, faster, easier job. I was frankly amazed just how easy it was. The appearance of the back 2 plugs on the passenger side looks much harder to access than it actually is.

To those who prefer to go through the wheel well , as I said above a few times, great, good for you. Bravo. If you have the extra time, extra tools, extra strength to lift the 100lb wheels off, and find it easier, then bully for you. It wouldn’t have been easier, or safer, or less hard on my body for me.

As a general comment I’d recommend anyone in poor physical condition not attempt physical tasks beyond their capacity. Hire a mechanic. Just not one who is in worse shape than you are, or you’ll be paying them to work at a snail’s pace. While you’re at it, hire a physician, physical therapist, and personal trainer because your health is worth far more than your car or the combination of every car you’ll ever own.

I mentioned the jack and jack stands . . . because it sounds like you’re the kind of guy who’ll also be doing his own brake job(s) in the future

Get those killer deals at Sears, before they disappear

They’ve been sending me “free cash” to spend on tools lately . . . same thing as a coupon, for all practical purposes

Neither a doctor or physical therapist are going to heal what age and injury have done to me and I will continue to do what I want, when I want to do it for as long as I want to. The loss of physical strength just means I have to use more leverage or ingenuity to accomplish things.