LS coil packs suggestion for L33
 

My 2005 GMC Sierra is getting a little sluggish. It has the 5.3 aluminum L33.

I am thinking about replacing the coil packs, plug wires, and spark plugs.

Any suggestions on brands? Or other parts tp change for maintenance?

It has a K&N filter in the stock housing, and I change the oil regularly with Mobil1.

BTW it only has 65K on the truck...

Thanks, Joe

I'd be very surprised if you need coil packs.

Change the plugs first, wires if they appear damaged, and maybe look to see if clogged fuel filter or something.

Thx Will

Check your fuel pressure, smoke the intake for vacuum leaks, make sure your exhaust manifold bolts aren't broken off. All very common problems, especially the rear and front manifold bolts. Also, the rear knock sensor likes to fill up with water as the seal ages and no longer fits tight in the valley cover. The harness also likes to crack with age and let the wire break.

I have done all of these dozens of times, each. Had some under 100k miles, had some that had 300k. Those pickups just don't die.

I've only once had to replace a bad coil on an pickup engine of the LS variety. It had 200k on it and had been in a field for 2 years.

Sorry I forgot to mention I bought it new and have never messed with it.

Where is the knock sensor?

The knock sensors (2) are located under the intake manifold. I wouldn't pull the intake manifold just to check them, but if you have access to a smoke machine, or have a buddy who smokes, fill up the intake with smoke (Pull the brake booster hose or similar, block the throttle body so all the smoke doesn't leave through the air filter) and make sure it doesn't leak by the base. Extremely common, although your lower miles may help.

If you intakes aren't leaking, don't pull your intake just to check the knock sensors/seals. The engine light will come on if the the harness to them brakes or if the corrode and stop functioning.

Plugs are a mileage replacement more than an age, so you could replace them but I doubt that's the issue. Cheap and easy though, so also a "why not".

Wires are more of a time/abuse/mileage replacement. I really doubt they are causing an issue, usually it's all or nothing with plug wires. They will either misfire or be fine....generally. That being said, they are easy to replace, although not incredibly cheap for a quality set (don't cheap out here, big no no).

I don't believe an '05 will have a fuel filter, but replace it if it does. If you can borrow a fuel pressure gauge, or have one, definitely go for a drive with it taped to your windshield. Find a big hill and go wide open throttle up it. It should maintain it's specified PSI, roughly 50-60 depending on your system (look up the specific, don't go by my generality). If your 8th VIN digit is a Z, you have a flex fuel system and can use E85. If it's a T, you don't have that. I believe both systems take different pressures, but it's off the top of my head so don't rely on that.

The exhaust manifolds bolts pop the heads off, alot. So often that Dorman makes a clamp to do repair it easily, although not cheap. We try to drill out the broken bolts, or weld onto them and turn them out when possible.

Usually power loss is due to inaccurate fuel trims, whether your MAF/MAP (usually MAF) is reading incorrect air coming in, a vacuum leak (usually intake manifold gaskets on those) letting unmeasured air come in, or an exhaust leak that is letting oxygen into the exhaust causing your engine to think it's lean (it will try to add fuel to compensate, messing with mileage and power). Without a good scan tool that shows long term fuel trims, it's a crapshoot.

The knock sensors will cause you to lose power, although they will trip the engine light when they are that bad. Without knock sensors, your engine doesn't know if it's pinging and will just retard your timing "in case" you get bad fuel.

Of course, there are tons and tons of other things that are possible, plugged cats and the like, but the intake leak, fuel pump, exhaust bolts, and knock sensors are definitely the most common.

So yeah... take that for what it cost you.

Thanks!

No problem. I work on these pickups daily, very common farm/high schooler pickup around here. I know of dozens over 200,000 miles on all original drivetrain. I only know of one engine that has blown, and that was due to a supercharger and a large body of water. Granted, not many high performance builds past a k&n and exhaust, but still, these are just indestructible pickups. Occasional transmission failure, usually due to trying to impersonate a 2500 or 3500 and haul way oversized trailers.

Wouldn't an L33 (gen 4) knock sensor located on the pass side of block, instead of under the intake?

A 2005 should be under the intake, they switched to the side mounts in 2007... I believe.

https://www.google.com/search?biw=16...FgrpjnqZE-vWM:

If it has that connector just above the fuel line(s) it is under the intake.

Also, on Wikipedia they list the L33 as a Gen 3. Not saying it's gospel...