classic valve spring symptoms
Misfire help! Video attached!
Thread Starter
Racer
Joined: Jun 2010
Posts: 360
Likes: 0
From: Chicago Illinois
Misfire help! Video attached!
Recentley I was driving my 02 zo6 and i punched it in 1st gear, when i shifted to 3rd, the motor kind of stopped for a second and then accelerated like normal. Traction control WAS off. When I got down to speed (10-15mph), the car sort of bogged and started to shake heavily. I pulled over and thats when I heard a loud "click click click click" coming from under the car near the motor. I pulled up my codes and there was a "p0300 h c" random misfire code. I checked the clutch and everything looks ok. I switched my spark plugs and wires around, also gapped the spark plugs without success. A local shop (corvette experience) said it sounded like broken lifters. I also checked my valve springs and none are broken. The ticking noise gets louder and faster when engine rpm increases. I will attach a short sound clip soon so please listen and let me know what you guys think it is. Any input will be appreciated! thanks!
Last edited by MyEBc5Z; Sep 24, 2010 at 12:00 AM.
Burning Brakes
Joined: Mar 2008
Posts: 983
Likes: 36
From: Middle Of Kali CA
You say you switched around wires and plugs. Did you see any burned wires as you have long tubes? Pulling wires off is usually a tug of war that can damage wires in the process.
The ticking is more of a concern as a missfire can be valve train related.
How many miles on the motor? Properly maintained and a stock cam, the C5 valve train is very good.
The ticking is more of a concern as a missfire can be valve train related.
How many miles on the motor? Properly maintained and a stock cam, the C5 valve train is very good.
Le Mans Master
Joined: Dec 2005
Posts: 8,562
Likes: 949
From: Communist Colorado
I would double check the valve springs. You can have a broken one and it could look ok. Smetimes its broken in just the right spot where it looks like its still in one piece. 2002 Z06 valve springs are notorious for breaking.
If you have a broken lifter its usually at the roller. The problem is that the needle bearings will let go into the engine and possibly cause more damage. You should be able to isolate the cylinder thats missing with a compression check. You can also use a stethascope to try to listen to the cylinders more closely. If you dont see any broken springs, fire it up and try to see if one of the rockers isnt moving like the rest also.
The heads need to come off to r&r lifters. You can do springs with the heads on.
If you have a broken lifter its usually at the roller. The problem is that the needle bearings will let go into the engine and possibly cause more damage. You should be able to isolate the cylinder thats missing with a compression check. You can also use a stethascope to try to listen to the cylinders more closely. If you dont see any broken springs, fire it up and try to see if one of the rockers isnt moving like the rest also.
The heads need to come off to r&r lifters. You can do springs with the heads on.
Tech Contributor
Joined: Jan 2007
Posts: 19,416
Likes: 1,144
From: Dyer, IN
What bank is the noise isolated to? What did the plugs look like on that bank. When you don't have the luxury of a Tech II, so the cylinders can be mapped, plug condition can help isolate a misfiring cylinder. I would at least do a leak down, and another inspection of the valve springs on the bank with noise is in order....it's not uncommon on LS6's.
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Melting Slicks
Joined: Jul 2010
Posts: 3,476
Likes: 91
From: Between Tally and Gatorville ,Florida
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
LOOK CLOSELY! Rocker trunnion puked roller bearings OR bent push rod OR bad spring.
Use a mechanics Stethoscope and try to isolate it to a bank and cylinder,
BC
Use a mechanics Stethoscope and try to isolate it to a bank and cylinder,
BC
Thread Starter
Racer
Joined: Jun 2010
Posts: 360
Likes: 0
From: Chicago Illinois
I'll try the compression tester tomorrow and recheck my valve springs and rockers. Let's say its neither of the three, then what would you guys think it would be? Because idk what else would cause a random misfire
Melting Slicks
Joined: Apr 2003
Posts: 2,150
Likes: 6
From: NS
It's either a broken spring (my guess), damaged rocker, bent pushrod, and less likely a damaged lifter. If it were me I wouldn't run the engine until I pulled the valve cover(s) and found the culprit. Should be easy to find. Definitely valve train related.
