Misfires again... - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

tuki3388 · 05-20-2017, 01:32 PM

Okay guys i'm really at a loss for words this time. I'm out of all warranty's, past the 5 year mark, and I have been having misfires from my car since the first couple years of owning it. It is a P0303 code that keeps coming back...

2012 Camaro 2LS
51k miles
Swapped coil packs
Cleaned carbon build-up 2x
Valves Cleaned Multiple times
Multiple new plugs
Multiple new injectors
Multiple new coils

3 dealerships ether can't fix it or get it to happen for them.

Got GM involved the last go around.

Thanks in advance!

Swacer · 05-20-2017, 01:45 PM

Trade in

Not the most helpful answer sure, but easier than the headaches you're going through.

tuki3388 · 05-20-2017, 01:49 PM

Haha yeah i've thought about it. It is just so close to paid off. That and I start my Masters Degree in the fall. Will definitely keep it in mind though.

JerTM · 05-20-2017, 01:54 PM

Get the valve springs checked. I fought an intermittent misfire on a 3.6L a few months ago. The valve spring was broken but wedged in a way that it would be fine for a while and then it would misfire a few days later. Yours may not be broken but it could be weak.

tuki3388 · 05-20-2017, 02:01 PM

Ill note it down thank you!

John_C · 05-20-2017, 02:14 PM

Check for vacuum leaks. They can cause all sorts of issues. Especially in the fuel system.

Had a Mustang with vacuum leak at the fuel tank that would buck, surge and miss.

tuki3388 · 05-21-2017, 05:26 PM

okay didn't know that but I will get it checked out.

JerTM · 05-21-2017, 06:03 PM

Although it couldn't hurt to check, a vacuum leak is highly unlikely to cause a misfire on one cylinder only.

Yasuo · 05-21-2017, 09:38 PM

Well, have you ever had any overheating issues? Oil leaks in the past? It's a long shot but have you checked to make sure your piston rings and cylinder walls are ok? A good way to check it is to check the compression of the actual cylinder itself and compare the psi reading to the other cylinders which are firing properly. If the psI reading is substantially low, pour some oil directly into the cylinder and check the compression again. Pouring oil into the cylinder will act as a temporary seal on the cracked piston ring and will bring the compression back up to normal until the oil is burned off. If that's the case, you're going to have to rebuild that cylinder.

hammdo · 05-21-2017, 10:40 PM

Ck cylinder #3 for the mis-fire. I'd ck the valve spring, wire, and plug. Also, those 'cleaning' sprays can cause issues if it released 'hard' carbon in the cylinder.

Has any mechanical work been done that may impact the misfire? Have you also checked the ground to the engine?

Did you do a compression and leak down test on the offending cylinder?

Just some suggestions...

-Don

05-20-2017, 01:32 PM	#1
tuki3388 Drives: 2012 Camaro 2Ls Join Date: May 2013 Location: Lafayette Indiana Posts: 35 View My Garage	Misfires again... Okay guys i'm really at a loss for words this time. I'm out of all warranty's, past the 5 year mark, and I have been having misfires from my car since the first couple years of owning it. It is a P0303 code that keeps coming back... 2012 Camaro 2LS 51k miles Swapped coil packs Cleaned carbon build-up 2x Valves Cleaned Multiple times Multiple new plugs Multiple new injectors Multiple new coils 3 dealerships ether can't fix it or get it to happen for them. Got GM involved the last go around. Thanks in advance!

05-20-2017, 01:45 PM	#2
Swacer Drives: 2018 GT350 Join Date: Nov 2011 Location: PA Posts: 2,719	Trade in Not the most helpful answer sure, but easier than the headaches you're going through. __________________ Off to the Dark Side

05-20-2017, 02:14 PM	#6
John_C LSx FTW!!! Drives: 2010 Camaro 2SS RS Join Date: Jan 2017 Location: TN Posts: 767	Check for vacuum leaks. They can cause all sorts of issues. Especially in the fuel system. Had a Mustang with vacuum leak at the fuel tank that would buck, surge and miss. __________________ 2010 2SS RS A6 781rwhp on E85 Stage 2 ProCharger D1X Circle D 3400 Triple Disc Kooks Jet Hot Headers Kooks Full 3in exhaust Trick Flow GenX 255's Polished PAC .660's & Ti-retainers TSP VVT 3.2 cam kit w/DoD Delete Smith Bro's Trunnion kit AEM X-Series OBDII Widebands FIC ID1300x Injectors GM ZL1 High Output Fuel Pump DSX Tuning Flex Sensor DSX Auxiliary Fuel System Tim King Stage 4 Max Effort CTSV 6L90 DSS 1 piece aluminum driveshaft JRE 6L80E / 6L90E Dipstick NGK Iridium IX spark plugs #7 heat range Mighty Mouse Camaro 5 Wild w/-12an and Billet Black HP Tuners VCM Suite

05-21-2017, 10:40 PM	#10
hammdo 'It's an experiment' Drives: [COTW 2/09/15] '11 GPI LSA SC Z/LE Join Date: May 2014 Location: Dallas TX Posts: 8,693 View My Garage	Ck cylinder #3 for the mis-fire. I'd ck the valve spring, wire, and plug. Also, those 'cleaning' sprays can cause issues if it released 'hard' carbon in the cylinder. Has any mechanical work been done that may impact the misfire? Have you also checked the ground to the engine? Did you do a compression and leak down test on the offending cylinder? Just some suggestions... -Don __________________ 747 RWHP 794 RWTQ "Horsepower sells cars, torque wins races." - Enzo Ferrari See My Build: http://www.camaro5.com/forums/showthread.php?t=385577

05-20-2017, 01:49 PM	#3
tuki3388 Drives: 2012 Camaro 2Ls Join Date: May 2013 Location: Lafayette Indiana Posts: 35 View My Garage	Haha yeah i've thought about it. It is just so close to paid off. That and I start my Masters Degree in the fall. Will definitely keep it in mind though.

05-20-2017, 01:54 PM	#4
JerTM Drives: 2011 2SS/RS M6 Join Date: Oct 2015 Location: Utah Posts: 1,941	Get the valve springs checked. I fought an intermittent misfire on a 3.6L a few months ago. The valve spring was broken but wedged in a way that it would be fine for a while and then it would misfire a few days later. Yours may not be broken but it could be weak.

05-20-2017, 02:01 PM	#5
tuki3388 Drives: 2012 Camaro 2Ls Join Date: May 2013 Location: Lafayette Indiana Posts: 35 View My Garage	Ill note it down thank you!

05-21-2017, 05:26 PM	#7
tuki3388 Drives: 2012 Camaro 2Ls Join Date: May 2013 Location: Lafayette Indiana Posts: 35 View My Garage	okay didn't know that but I will get it checked out.

05-21-2017, 06:03 PM	#8
JerTM Drives: 2011 2SS/RS M6 Join Date: Oct 2015 Location: Utah Posts: 1,941	Although it couldn't hurt to check, a vacuum leak is highly unlikely to cause a misfire on one cylinder only.

05-21-2017, 09:38 PM	#9
Yasuo Drives: 2010 Camaro SS LS3 Join Date: Oct 2016 Location: Florida Posts: 45	Well, have you ever had any overheating issues? Oil leaks in the past? It's a long shot but have you checked to make sure your piston rings and cylinder walls are ok? A good way to check it is to check the compression of the actual cylinder itself and compare the psi reading to the other cylinders which are firing properly. If the psI reading is substantially low, pour some oil directly into the cylinder and check the compression again. Pouring oil into the cylinder will act as a temporary seal on the cracked piston ring and will bring the compression back up to normal until the oil is burned off. If that's the case, you're going to have to rebuild that cylinder.