SmilinSam

There are so many smart people who have so much knowledge regarding the Z06 on this forum I am hoping someone out there can give me some advice.
18 Months ago the CEL came on, threw codes P0356 and P0300 indicating a misfire in cyl 6. swapped coils on cyl 6 and 4. misfire still on cyl 6, checked wiring on coil bracket, swapped coil assemblies, still missing on cyl 6. decided it needs a new ecm. Ecm replaced. Problem seemed fixed.
Fast foreward to two weeks ago-CEL back on. Another P0300 code misfire on cylinder 6 again. Swapped ignition coils and wires again, misfire stayed on cylinder 6. Flushed injectors and problem remained on cylinder 6, swapped injectors, stilll misfire on cylinder 6. Inspected for broken valve spring and found springs in good order.

He now believes that the camshaft lobe hardening surface has become compromissed, and tells me that he is 85-90% sure that that is the cause. The other cause he says could be a collapsed lifter. Either way the only way to know for sure is to remove the heads and examine.

The car is a 2008 with approx 30k miles on it. To me that seems like a very low number of miles to need a camshaft replacment. I am very hesitant to go ahead with tearing the engine down not knowing if this is the issue for sure.

Any advice from the people who are smarter than me about this car (and there are many) would be appreciated.

Bill Dearborn

You say you have P0300 but nothing about any other code. Are there any other codes now? How do you know it is cylinder 6 this time? It seems if it is caused by a mechanical condition that could be checked by running a compression test Vs tearing the heads off.

Has the wiring from the ECM to the ignition coils been checked? If it is truly # 6 that is misfiring this time it might mean the replacement of the ECM may have covered up a connector problem Vs an ECM problem and now the connector problem is back.

Bill

stefuel

Well if you're sure it's #6, pull the valve cover off. Pull and inspect all spark plugs. Pick up a cheap dial indicator and set it up over the oil hole in the rocker arm above the pushrod. spin the motor over by hand and note how much movement the intake and exhaust move. Then compare those readings to any other set of valves on that side. If all is well and you're sure all your wiring is correct, put it back together and install a new set of plugs. Go to Auto Zone or whatever and pick up a couple of bottles of Techron fuel system cleaner. Run a couple of tank fulls at full strength or better. This will clean your whole fuel system AND remove any deposits on your valves that might cause them not to close consistantly and fully.
This was GM's quick fix for sticking valves in my wifes Tahoe that was causing random mis-fires.

Landru

Premature lifter/cam wear isn't unheard of for a small percentage of Chevrolet small blocks, used to be notorious w/ older generations.
Lost two on my '80 L-48, had 'soft cams', wore out rather fast taking the lifter with.
While an '80's not modern era I continue to read instances on C5 & C6 General complaining about "bad cams/lifters".
Poor oiling and/or hardening's usually blamed.

Thing is I thought the oiling problem was addressed in the LT & LS motors, and hardening's an art form these days. Right

After exhausting the above mentioned good suggestions, the only way you'll know for sure is to open it up and look.
If it were my '08 Z, I'd replace cam/lifters & have the heads rebuilt while open, but that's me.)

G/L, will be following to learn what you find.

carpe dm

Sam:
Please let us know how things go....

Dirty Howie

You mention everything except trying a NEW SPARK PLUG !!


DH

stefuel

He didn't but I did.

BLWN427

A compression and leak down test will tell you just about anything you need to know as far as a valvetrain or mechanical problem with the engine. A skilled mechanic should be able to do both in a few hours. And cost you far less than tearing into the engine.

Does the car mis all the time? Randomly?
Only when hot?

I only ask because you said the problem went away after the ecm install. Which leads me to think it is nothing mechanical at all but more along the lines of fuel or spark related.

I would start with the compression leak down first. Then once that checked out I would install new properly gapped plugs, wires, check all grounds, and oddly enough even a bad battery can cause some seriously weird codes from these cars.

z06clif

Marvel Mystery Oil ............. Remember that ?

Clif

SmilinSam

so I checked all the wires and connectors I could get to and see. They all seemed fine. I put a new spark plug in cylinder 6, cleared the codes and started it. After a minute or two I get the message service traction control, then shortly after that the CEL comes on. After a few minutes it goes out and the service traction control goes out as well. A minute or two later they both come back on. Then the service traction control goes out just leaving the CEL on. When I checked for codes I get P0306 again! Code was set at idle on a cold engine

Next I drove the car at highway speeds for 30 min, CEL stayed on the entire time. Car is now warmed up. I decided to see if it throws the code after it is warmed up, so I cleared the code again. I then drove it for the next 2 hours at a variety of speeds, in the city, on the freeway, stop and go, let it idle for 5 minutes, turned it on and off several times and no codes or lights came on. Today after it sits all night I start it up again and let it idle. I get the same thing happen with the CEL and the service active handling. I check for codes and I again have a P0306 code. It appears that it is only throwing the code on a cold engine at idle on start up. If its warm no codes. I am not sure what to make of this. Does this really sound like it could be the camshaft?

one more piece of information. Just before I started it the first time the battery read 11.6 volts. After I got back from my 2 and a half hour drive the battery read 12.7 volts. When I restarted it today I checked the voltage and got 12.5 volts on start up. So I dont think its the battery causing the problem

Vito.A

The addition of the Traction Control message may mean its an Electromagnetic Interference issue (EMI), not a flat cam lobe.
What spark plugs and wires are you using? NGK plugs have been known to cause interference problems.
Also check the alternator wires. Completely remove the large red charging wire, clean the terminal and then remove the black weather pack connector on the alternator top rear and check for corrosion.
Check both battery terminals. How old is the battery?
There is a ground wire on the right rear cylinder head close to the firewall. Check it for corrosion.
Ohm the #6 plug wire and carefully check the spark plug.
Does the car feel like it's missing?

Mig233

Not sure if this will help in your situation but my buddy has a 2011 Grand Sport, and had a similar issue pop up suddenly. Cylinder X misfire and traction control/active handling was disabled. The TC/AH system only work properly when the engine is running properly. If the system detects a fault, it cannot accurately dial back throttle inputs in a low traction situation.

Before knowing this information, I was thinking it had to be some ECM problem that was affecting both of these systems. Turns out the problem was something much less harmless...After popping the hood, one of the plug wires popped off (apparently this is pretty common with LS3s). Put it back on, and all was well.

PS, it totally sucks that you can't read and clear codes from the DIC in the C6s, like you can in the C5s.

z06clif

I am assured by my clergyman if you lead a clean life and die in the state of grace that will be revealed to you upon entering Heaven. That and the JFK thing LOL

Clif

kcbc

1.) ask ur mechanic if he ever done a runing compression
2.) ask a real mechanic to do a vacuum transducer wave form that can identify the vac and pressure during the event at #6 cyl and compare it with other good cylinder
3.) lets assume theres a ban flattened out cam lobe.....compression(static) only can tell how much the cylinder can seal and whats the value after the powerstroke cyle .....leak down only test how much sealing a particular cylinder can hold ....even if u just use only the outer spring to secure valve close ...it will still test negative and show a
within spec pressure .....


I totally disagree on compression and leak down can tell u everything
mechanically on an engine

Mr. Gizmo

I would try a new battery and run a check on the alternator