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Knock When Starting Engine


Full Member
Jan 1, 2003
Las Vegas, NV.
Hey all, I just purchased my '03 Z66 Avalanche two days ago! I think I might already have a problem.

Whenever I start my engine, I hear a single audible knock coming from the engine. It sounds almost like a spark knock or maybe even a valve. It is only a single "knock" when starting. Everything is fine after that. No problems whatsoever. Everything seems to be in good working order and the truck runs excellent.

Is this normal for the Chevy engines, or should I just go ahead and take it in? Should I wait until my 3,000 service to see if it might go away on it's own?
It's just one single knock, and then no other noises?

It is possibly the starter gear engaging and hitting the flywheel? (normal, how it should work, maybe a little noisy)

Or maybe the engine starting, and the starter gear retracting back in the housing?

I'm pretty sure my engine makes a little tick when it catches. It's not something I really pay attention to, so your's might be something else? :cautious:
Yeah, just a single knock. It is quite audible. You can hear it from inside the truck when you start it. Even my wife noticed it.
if the wife notices- which most never do!
get it looked at LOL...

I have that carbon build up after 10K miles and the dealer states it is normal but DRIVES me NUTTY!
Nothing I can do though-
get it looked at as this is why we have 36K waranties....

Good Luck
Mine does the same thing, but not each time. Maybe 90%.

I tried turning on the ignition and waiting couple of seconds, but doesn't seem to effect anything.
That's real strange...

I went out during lunch and took a ride around. I didn't really notice any noise from mine... :cautious: Sorry...
Ya, one knock on start-up.

Today, I turned the key and waited a couple of seconds before starting, and no knock.

I'm going to try and remember to do this consistently and see if it makes a difference.
I have an 03 with 422 miles and it also makes
a single knock when I start it. I have not
really sat and listened to try to figure out
where it comes from. Maybe the starter
kicking in...but it did raise my eyebrows when
I first heard it.

Love the truck though! Much better than
the POS Land Rover I was driving before!

My '03 has 1000 miles on it and it makes a little lifter sound on fire-up but it goes away after about 30 seconds.

I think its the 5w-30w oils that are now used. I bet it is normal for these engines to do this. I'm not worrying until it gets worse if if ever does at that.
man, mine would 'Knock' your socks off. I would wait till some tourist would wander to close to my Av and BAM. I think some of them soiled them selves. I am fairly heartless some times >:D

My dealer replaced the starter under a noise complaint
the new one is much quieter :7:

now the water pump is the only noise under the hood now. Nothing that concerns a retired wrencher
The starter knock or crack noise is common to all the Chevy trucks. Suburbans, Tahoes and Silverados do it. I have the same complaint and with 26000 miles on my AV it has not gotten any worse.

It is the noise that the solonoid makes as it retracts the starter gear once the engine fires.

I also would get that single knock on start up I will wait and see I thought it was part of the break in. I have 75K and 72 mo extended warrenty hope I dont need it though.
metal smacking metal can never be good.
It will not cure its self. Luckily its only beating its self up. Mine banged away for 34,000 miles.

It worked fine, even the day it was replaced. You don't have to live with the annoying noise.

No extended warranty for me. It's like,

wire walking without the net
playing football with out a cup
playing tennis with no balls
no jockeys or boxers, free ba**in
a cat without claws
a dog with dentures, bark is worse than bite
peeing up hill with a head wind
swimming to Hawaii
3rd class on the Titanic
A vasectomy

>:D >:D >:D
vegasshawn, my 02 z71, 5.3 has a noise on startup, not the piston slap, which ticks , but a crisp kind of"spark knock"

maybe the computer, advances the timing, when starting, but i think that is the noise you hear, one distinct, kind of loud click.

i mentioned this many months ago, and after 25000 miles, no problem from this.

and i use my truck for work, and start it up about ten times a day!

maybe, all along it has been the starter??
I'll have a knock on start up on my '02 Z-71 with 24K miles when it is cold and damp out. It goes away after a second or two - I'm guessing it has to do with timing with the weather conditions.
I Have heard that the knock has been a problem with all 5300 Vortec models. Has anyone with a 2002 heard this knock. I have a 02 Z66 and I heard it when it was new but now with 30k miles I dont hear it or I am used to it.
I had a 99 Camaro SS with a similar issue. Turned out to be the notorious piston slap issue with the LS1 engines. Here is a GM notice for our trucks. Could be you have the starter issue, however this could also be part of the problem...I would probably have your dealer check it out, maybe mention this tech. brief # when you go.

TSB #02-06-01-038
Engine Knock or Lifter Noise (Replace O-Ring) #02-06-01-038 - (12/02/2002)
Engine Knock or Lifter Noise (Replace O-Ring)
2001-2002 Chevrolet Camaro

2001-2003 Chevrolet Corvette

2001-2002 Pontiac Firebird

2002-2003 Cadillac Escalade, Escalade EXT

2000-2003 Chevrolet Suburban, Tahoe

2001-2003 Chevrolet Silverado

2002-2003 Chevrolet Avalanche

2000-2003 GMC Yukon, Yukon XL

2001-2003 GMC Sierra

with 4.8L, 5.3L, 5.7L or 6.0L V8 Engine (VINs V, T, Z, G, S, N, U -- RPOs LR4, LM7, L59, LS1, LS6, LQ9, LQ4)

Some customers may comment on an engine tick noise. The distinguishing characteristic of this condition is that it likely will have been present since new, and is typically noticed within the first 161-322 km (100-200 mi). The noise may often be diagnosed as a collapsed lifter. Additionally, the noise may be present at cold start and appear to diminish and then return as the engine warms to operating temperature. This noise is different from other noises that may begin to occur at 3219-4828 km (2000-3000 mi).

The O-ring seal between the oil pump screen and the oil pump may be cut, causing aeration of the oil.

Inspect the O-ring seal and replace as necessary. Use the applicable part number listed below. Refer to the Engine Mechanical sub-section of the appropriate Service Manual.

Parts Information
Part Number

Seal-O/Pmp (O-ring)

(F and Y Cars)

Seal-O/Pmp (O-ring)

(C/K Trucks)

Parts are currently available from GMSPO.

Warranty Information
For vehicles repaired under warranty, use:

Labor Operation
Labor Time

Pickup Tube and Screen - Replace
F Car
3.7 hrs

Y Car
4.3 hrs

C Truck
1.3 hrs

K Truck
2.1 hrs

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information. WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION


Hope this information helps. Let us know what you find out.

I have a 2002 Av 1500 4WD and I have not had any knocking noise but I went and looked at 2 2003's one 1500 4WD and one 2500 4WD the 1500 did not have a knocking noise but the 2500 had one and when I pressed on the gas pedel it got faster
I noticed the knock right off. I never had a sound like it in any other vehicle. I have been paying attention to it lately and I think I found a pattern to it. Seems to be worse when it's colder. It really makes the engine sound cheap.

When I used to start, I let go of the starter AS SOON AS I HEAR IT PRETTY MUCH START TO TURN OVER. The engine then jolts itself over and that seems to be the knock sound.

I found that when I hold the starter JUST A HAIR LONGER that it does not seem to do it, as the starter is doing more of the work instead of the initial few combustions bringing the engine up to speed.