Donohue

I bought this z06 a few months ago. Unfortunately the mods are a bit unknown because the owner didn't keep the receipts from LG . Either way, it does have a full exhaust, cam etc. Anyways, when I bought the car, it was smoking but my first/optimistic thought was that it was running rich. Anyways, I have had the car for about 3-4 months and have driven it about 200 miles. I looked under the car a couple days ago, and it seems as though the car left an oily film throughout the bottom of the car when I left the cutouts open. I did get an oil catch can installed, hoping that would fix the issue, but no luck. The smoke is a light grey, and sometimes is barely noticeable. But sometimes if I'm sitting at a light, it gets a bit extreme/embarassing. It appears to do it mostly, if not only, at idle. I got on it a bit a couple weeks ago, and my gf was behind me, and mentioned it throwing smoke out. My MPG doesn't seem bad, so does this seem like a running rich issue, or something more serious? I haven't had the time to get it retuned, but wanted to get some opinions from you guys.

Donohue

By the way, the car does die/have a weak idle sometimes. But overall the car is stout power wise.

1999_TRC

That's not called optimism, it's call denial.

Donohue

Not really. I've had cammed LS1 cars that ran rich/smoked at times.

EDIT:

I met the guy halfway from San Antonio/Dallas at a Starbucks. Didn't have the means to get the car looked at.

But I will say he didn't mention the smoking prior to me meeting up with him, I have a feeling the car sat.

lucky131969

At this point, you will have to run the tests yourself. Do a compression and leakdown test. Inspect the plugs, to see if there is a particular cylinder that is having problems. Check the intake for oil. Get the car to a tuner, so the tune can be verified, and establish a baseline.

Donohue

I got the plugs changed, the shop said nothing looked out of ordinary. I'm hoping to get the car dropped off at a tuner this next week.

EDIT:

The car also bucks/surges sometimes.

Donohue

I got the oil changed a few weeks ago, drove it 50 miles since, and I checked the oil earlier today and it is right at the add line. When I first bought the car the coolant level was low, I filled it when I got home and it hasn't budged. 2 codes were pulled a couple months ago. I wrote them down, but have misplaced the damn paper. One of the codes was for the Traction control though. Check engine light is not on at the moment. The plugs were pulled, the shop said they looked fine.

Donohue

Just a bit of an update. I got the car retuned, put down 465RWHP. The tuner said it was only the second car that he's seen put down that kind of power through an LS6 intake.

The car is still smoking, he said it's oil.

I'm hoping to do a compression test tomorrow. The shop was suggesting valve stem seals or valve guides? *fingers crossed* Said they highly doubted that it was the rings bc the engine is stout power wise. Do you guys agree?

TXGS507

my guess would be valve seals/guides as well... should be a fairly simple fix... 465?? wow.. that is rediculous! GL my friend

sfc rick

I currently have mine tore down and found that the heads needed to have a valve job and valve guides replaced. The symptons were engine would puff out a cloud of blue/greyish smoke on start up then the smoke would go away. It wasn't until about 3 months later it would even smoke at idle. Decided it was time for rebuild, but when I pulled the intake manifold I could see oil inside the intake passage way on the heads pooling on the intake valves and valve seats. That was the reason for the oil smoke! Once I pulled the heads off it was apparent the valve guides had to be replaced, and the engine block was fine!

You should pull your intake manifold off and look down your heads intake passage ways and see if it's full of oil too.

Here is my original thread on what I found,

http://forums.corvetteforum.com/c5-g...e-problem.html

kp1

If I had to guess I'd say you have some valve guide seals that didn't get fully seated when the cam was installed, or maybe someone screwed up & put intake seals on exhaust valves. In any event, I'd be pulling the valve covers & to check seals because if the engine really only has 17K miles, there shouldn't be valve guide or ring issues.

If you pull the dipstick does the oil smell like gas? Is the oily coating under the car coming out of both cutouts or just one?

lucky131969

I'm really surprised they agreed to dyno the car...when they knew it was burning oil If it was my shop, I would have insisted the oil burning problem be fixed first.