Trouble shooting misfire

Tech discussions on the L77 6.0L V8.
Post Reply
Jt.kline19
Posts: 16
Joined: Sun Jul 31, 2016 11:42 pm

Trouble shooting misfire

Post by Jt.kline19 »

On my way home my 2012 PPV's warning lights came on all at the same time. I could her a ticking noise which sounded like a misfire, and the engine was not operating in its normal manner. The check engine light was flashing, and the stabilitrak fault indicated on the led screen, the traction control light was also on. I took it to a buddies house to scan it, and notice while idle at a light the engine light would stay solid, and the stabilitrak and traction would turn off. Once the vehicle was moving about 20 ft the lights and indicators came back on. Even while idling I could still hear the ticking, and sounded like the car would backfire while attempting to accelerate. I believe it gave me a go of P0300 of Random Misfire, and low oil pressure. I understand this could be numerous things causing a misfire. I have changed the spark plugs and still have the misfire. Im just curious to know if someone else has had this same issue. In the morning I am going to buy a spark plug tester to figure out which cylinder is causing the misfire. Basically since the spark plugs are changed, my next step is to change the spark plug wires. The vehicle has around 101,500 so I'm sure its time for some maintenance on these type of parts. Any input would be appreciated.

Thanks
Jesse
jackleg
Posts: 99
Joined: Wed May 04, 2016 9:25 pm
Location: SW MI

Re: Trouble shooting misfire

Post by jackleg »

The Stabilitrack and Traction are probably being disabled while the misfire is current. So figure out the misfire and all should be good.
2011 9C1 6.0
RCR "Little Lunati" 219/223 .625/.625 112+0
Kooks headers, hi flow cats, Dynomax Super Turbos
Flex fuel tune
CrashTestDummy
Posts: 2300
Joined: Sat Feb 07, 2015 2:31 pm
Location: Pearland, Texas

Re: Trouble shooting misfire

Post by CrashTestDummy »

Pull the valve covers and watch the rockers when you crank the engine over. I'll bet you probably have a failed(ing) lifter. The tick noise and the low oil pressure code point to that.
Gene Beaird,
Pearland, Texas
2012 Caprice 9C1
1992 B4C 1LE Camaro
2018 Tahoe PPV (her car)
1995 DGGM Impala SS
1985 Firebird - 310 LS1 C Prepared autocross car.
1980 Bluebird Wanderlodge
And some others
Do YOU have my SPID?
Jt.kline19
Posts: 16
Joined: Sun Jul 31, 2016 11:42 pm

Re: Trouble shooting misfire

Post by Jt.kline19 »

So I'm positive I have a lifter failure in cylinder 6. I'm lookin at the lifters, and this seem like a dumb question, but I just want to make sure. There are two different types I'm finding. Seem to one with cylinder deactivation, and one for no active fuel management. I'm assuming I need the cylinder deactivation type since the vehicle have 8 and 4 cylinder mode. Also would it be wise to just replace all 16 lifters or just the one that has failed?
jackleg
Posts: 99
Joined: Wed May 04, 2016 9:25 pm
Location: SW MI

Re: Trouble shooting misfire

Post by jackleg »

The engine has both types of lifters depending on where they are located. It would be a lot of work to only change 1 lifter. You have to remove the cylinder heads to get at the lifters + you need gaskets and bolts. I would disassemble to evaluate the condition of the camshaft and then make a decision
2011 9C1 6.0
RCR "Little Lunati" 219/223 .625/.625 112+0
Kooks headers, hi flow cats, Dynomax Super Turbos
Flex fuel tune
Jt.kline19
Posts: 16
Joined: Sun Jul 31, 2016 11:42 pm

Re: Trouble shooting misfire

Post by Jt.kline19 »

jackleg wrote:The engine has both types of lifters depending on where they are located. It would be a lot of work to only change 1 lifter. You have to remove the cylinder heads to get at the lifters + you need gaskets and bolts. I would disassemble to evaluate the condition of the camshaft and then make a decision
Jt.kline19
Posts: 16
Joined: Sun Jul 31, 2016 11:42 pm

Re: Trouble shooting misfire

Post by Jt.kline19 »

Personally I don't think the cam shaft is an issue since it just happened. I haven't driven it at all, and it's only been turned on to evaluate that. Could someone provide me with a list of which cylinder has the different type of lifter?
Jt.kline19
Posts: 16
Joined: Sun Jul 31, 2016 11:42 pm

Re: Trouble shooting misfire

Post by Jt.kline19 »

UPDATE:

Well, I have the misfire all figured out, I ended up changing both lifters out of cylinder #6. I inspected all the lifter in this bank, and found them all to be in good shape (except for the one that failed). The rollers were not worn and appeared to be in good condition. I have the vehicle all back together, and ran it for an hour (idle only) and did not get any visible leaks, no lifter knocking. The head gasket appears to be holding up just fine. I did not have anything new jump out on the instrument panel while the vehicle ran. My only concern is the stabilitrak was still giving a warning that it was not functioning. I know while driving when the lifter went out this indicated turned off on idle at a stop light, but would turn back on while I drove. I'm thinking it will turn off once I test drive it in a day or two.
Post Reply