jcapored

1999 C5, engine/exhaust is stock except for Vararam intake. 48,000 miles (I am the original owner). Changed plugs at 40,000 miles. Previous plugs very clean when I changed them. I started HPDE events a year ago, approximately 8 events, and 8,000 miles on these spark plugs. Two days ago the engine light went on (started running rough). OBDII reading P0303 (cylinder #3 misfire). Plug #3 is quite fouled, burnt oil (see picture). Looked at plugs #1` and #5 and they are clean. I am using more oil that previously, but I assume it is the track-days (I do not drive it much between events). At least 1 quart per track day.
Is this the “LS1 Cylinder Ring/Engine Valley Problem” (Chevrolet Document ID #894549)?
I have not had a pressure check yet. Will pressure check reveal the Ring problem?
I will try running at low RPM’s on the street for 1000 miles, If Ok, should I live with it and just change plugs after HPDE Events?
Recommendations?
What is the typical cost of the Ring fix?

C5Natie

Looks like your pcv system is sucking in quite a bit of oil during the hpde. I would look at a good catch can setup first or maybe upgrading to a LS6 valley cover. Im pretty sure thats your problem and its fouling up your plugs. If it were your rings you would see smoke come out through the oil neck filler like a train while the engine is running.

C5Natie

Look inside your intake manifold. Im sure theres a nice puddle of oil in there.

sami85L98

Oil valve seal problem to me, leak down test will reveal where the problems if you have compression issue though, vacuum test also can be hook up thier diagnostic charts on google search.

Also use boroscope into #3 cylinder to see if too much carbon buildup or oil leak from valve seal or valve guide wear.

If valve seals than put a good #3 spark plug, and see if you get smoke at when you step on gas heavy acceleration and smoke disappear once car get going. Not a big deal to replacing valve seals.

Bill Curlee

PCV issues would NOT cause an issue with just ONE cylinder. Ring or valve guide issues will. Do a compression and leak down test and if good, replace ALL your valve guide seals.

Its still a very good idea to install a quality catch can and up grade your PCV system to the 04 style.

Especially if you are doing high speed high RPM events.

Bill

jcapored

Thanks Bill - I was thinking the same thing about the PCV issues (would not be isolated to just #3 cylinder). How big a job is valve guide seals? is this a DIY job, 4 out of 5 type difficulty thing, or does it require specialized tooling and machines?

Bill Curlee

Valve guide seal replacement can be done in place with out much difficulty.

I, remove all the spark plugs, place the cylinder at BDC, thread a good length of clothes line rope into the spark plug hole and then HAND TURN the engine until the piston stops. That keeps the valves on that cyl from dropping into the cylinder. Use a store purchased LS engine spring compressor.

Some people use compressed air in that cylinder to keep the valves shut. I like rope.

Compress that spring, remove the keepers, the retainer, the spring, the seal, install the new seal.

Note! (The intake and exhaust use different rubber material seals) Reinstall in reverse the order.

NOTE! I recommend replacing the springs if you have much over 50K miles on the engine.

Scale of 1-5 = 3.5

U Tube is your friend:
BC

GO_BLUE_VETTES

What was your ultimate resolution? Valve stem seals or rings?

Did you observe oil in the intake?