Ls2 c6 misfire
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From: Gray Tennessee
Ls2 c6 misfire
After my C6 sat for several months I drove it and now it has a misfire. I have a new battery and alternator is putting out and the battery is receiving a charge.
I let it idle a few minutes and since I don't have an IR I touched all 8 header tubes. They were all warm and all were hot except cylinder number 3. All others I could only touch for a second but number 3 I could touch for several seconds.
So I think at least number 3 is the problem. It is not appearing to throw a DTC and the CEL will flash but not all the time. Sometimes it flashes and sometimes it does not.
Any advice on what to check, diagnose fix it. The plugs and wires are fairly new, less than 2000 miles. They do have heat socks on them also. I have not replaced anything yet and wanted to check here and see where I should start.
Thanks in advance for your help.
I let it idle a few minutes and since I don't have an IR I touched all 8 header tubes. They were all warm and all were hot except cylinder number 3. All others I could only touch for a second but number 3 I could touch for several seconds.
So I think at least number 3 is the problem. It is not appearing to throw a DTC and the CEL will flash but not all the time. Sometimes it flashes and sometimes it does not.
Any advice on what to check, diagnose fix it. The plugs and wires are fairly new, less than 2000 miles. They do have heat socks on them also. I have not replaced anything yet and wanted to check here and see where I should start.
Thanks in advance for your help.
Le Mans Master
Joined: Dec 2004
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From: West coast CA
After my C6 sat for several months I drove it and now it has a misfire. I have a new battery and alternator is putting out and the battery is receiving a charge.
I let it idle a few minutes and since I don't have an IR I touched all 8 header tubes. They were all warm and all were hot except cylinder number 3. All others I could only touch for a second but number 3 I could touch for several seconds.
So I think at least number 3 is the problem. It is not appearing to throw a DTC and the CEL will flash but not all the time. Sometimes it flashes and sometimes it does not.
Any advice on what to check, diagnose fix it. The plugs and wires are fairly new, less than 2000 miles. They do have heat socks on them also. I have not replaced anything yet and wanted to check here and see where I should start.
Thanks in advance for your help.
I let it idle a few minutes and since I don't have an IR I touched all 8 header tubes. They were all warm and all were hot except cylinder number 3. All others I could only touch for a second but number 3 I could touch for several seconds.
So I think at least number 3 is the problem. It is not appearing to throw a DTC and the CEL will flash but not all the time. Sometimes it flashes and sometimes it does not.
Any advice on what to check, diagnose fix it. The plugs and wires are fairly new, less than 2000 miles. They do have heat socks on them also. I have not replaced anything yet and wanted to check here and see where I should start.
Thanks in advance for your help.
Try swapping coils to see if the suspect cylinder moves with it.
Many code readers will show you the misfire counters in real time. A minimum misfire count must be reached to set a DTC.
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From: Gray Tennessee
So check the plug and wires, then deal the coil pack.
Do I need to physically swap it or just swap the plug wire and coil wire inputs, I have not looked but the wires may be to short to just move wires and not the actual coil pack.
The CEL flashes but not all the time. When I first start it with a cold engine it seems ok, it's only after it gets a little warmer, 150+ that the CEL starts flashing and even then not all the time.
I will see what I can do to swap it and see if it moves to the other cylinder.
Do I need to physically swap it or just swap the plug wire and coil wire inputs, I have not looked but the wires may be to short to just move wires and not the actual coil pack.
The CEL flashes but not all the time. When I first start it with a cold engine it seems ok, it's only after it gets a little warmer, 150+ that the CEL starts flashing and even then not all the time.
I will see what I can do to swap it and see if it moves to the other cylinder.
Race Director
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Start with pulling/swapping locations of the spark plug and plug wire with another location, and see if the miss fire moves with the swap.
If it does not, then pull the coil at the location of the miss-fire, and another coils to swap their location to see if the miss fire moves with the coil.
If miss-fire is staying with the cylinder after the above, then check the coil wiring, and do a compression test on the cylinder.
If it does not, then pull the coil at the location of the miss-fire, and another coils to swap their location to see if the miss fire moves with the coil.
If miss-fire is staying with the cylinder after the above, then check the coil wiring, and do a compression test on the cylinder.
Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
Since the car sat for a few months I would lean towards an injector being clogged...try some Techron in your tank...without some specialized diagnostic you’ll only be guessing and swapping parts !!
Last edited by C5 Diag; Apr 11, 2020 at 09:19 AM.
Melting Slicks
Joined: Apr 2019
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From: Northern Wisconsin
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,600
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From: Cape Coral, Florida
Good, informative video. One thing I didn't quite understand was that several times he stated that he was checking the secondary ignition signal with his scope, and the scope showed an ignition signal, but it was only about 2 volts. I would expect to see a secondary ignition signal somewhere around 50,000 volts. Could he have been checking the primary signal rather than the secondary?
Last edited by C5 Diag; Apr 11, 2020 at 01:22 PM.
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From: Gray Tennessee
I don't have any of those fancy tools, so I have to do it the hard way.
I did swap the coil pack from cylinder 3 (cooler one) to cylinder 2 and started it. I want to add a few details after this, but, after the switch I started it and checked again. The misfire DID NOT move with the coil pack move so cylinder 3 is still cooler than the others. So I will swap the plug wire and try it, then the plug and try it, and if it is still number 3 then it is either a fuel injector or a short causing the injector or coil pack from firing.
I hope it is not something worse.
This I find strange, the flashing CEL does not happen immediately. Only after the engine gets to about 135 degrees or more then it flashes. Why would it not flash until over 125 or so in temperature?
I did swap the coil pack from cylinder 3 (cooler one) to cylinder 2 and started it. I want to add a few details after this, but, after the switch I started it and checked again. The misfire DID NOT move with the coil pack move so cylinder 3 is still cooler than the others. So I will swap the plug wire and try it, then the plug and try it, and if it is still number 3 then it is either a fuel injector or a short causing the injector or coil pack from firing.
I hope it is not something worse.
This I find strange, the flashing CEL does not happen immediately. Only after the engine gets to about 135 degrees or more then it flashes. Why would it not flash until over 125 or so in temperature?
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From: Gray Tennessee
Ok, test number 2... results.
I swapped the PLUG WIRE and SPARK PLUG BOTH from cylinder 3 (Problem Cylinder) over to cylinder number 4 and repeated the start, idle to light flashes, check header temperature process.
RESULTS
The problem moved from cylinder 3 to cylinder 4 now. So, the problem is either the plug or the wire.
I will swap wire only from 4 back to 3 and see what happens. If 3 becomes the problem again then the wire is bad, if 4 remains the problem, then the plug is bad.
The plug was wet and black but not sure if its because of the wire or plug, will update soon.
I swapped the PLUG WIRE and SPARK PLUG BOTH from cylinder 3 (Problem Cylinder) over to cylinder number 4 and repeated the start, idle to light flashes, check header temperature process.
RESULTS
The problem moved from cylinder 3 to cylinder 4 now. So, the problem is either the plug or the wire.
I will swap wire only from 4 back to 3 and see what happens. If 3 becomes the problem again then the wire is bad, if 4 remains the problem, then the plug is bad.
The plug was wet and black but not sure if its because of the wire or plug, will update soon.
Thread Starter
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From: Gray Tennessee
UPDATE
Swapped PLUG WIRE ONLY from cylinder 4 (cool one) over to cylinder 3 and repeated process.
RESULTS
Cylinder number 4 stayed cooler and DID NOT SWAP to cylinder 3.
SUMMATION
BAD PLUG
I will buy a couple tomorrow at Autozone and replace and see how it goes. I may replace all 8 as a precaution or do you guys think that is not necessary. The plugs only have about 1500 normal street and highway driving on them. So should I replace all 8 or just buy 1 or 2 just in case?
Also, I am running AC DELCO and should I stick with them or can you suggest something better to increase performance and reduce fouling or this happening again. I usually use E3 but any suggestions?
Naturally Aspirated but has CAI and LG Long Tube Headers, no CATS and OFFROAD X-Pipe and a tune.
Thanks and fingers crossed this fixes it...
Swapped PLUG WIRE ONLY from cylinder 4 (cool one) over to cylinder 3 and repeated process.
RESULTS
Cylinder number 4 stayed cooler and DID NOT SWAP to cylinder 3.
SUMMATION
BAD PLUG
I will buy a couple tomorrow at Autozone and replace and see how it goes. I may replace all 8 as a precaution or do you guys think that is not necessary. The plugs only have about 1500 normal street and highway driving on them. So should I replace all 8 or just buy 1 or 2 just in case?
Also, I am running AC DELCO and should I stick with them or can you suggest something better to increase performance and reduce fouling or this happening again. I usually use E3 but any suggestions?
Naturally Aspirated but has CAI and LG Long Tube Headers, no CATS and OFFROAD X-Pipe and a tune.
Thanks and fingers crossed this fixes it...
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,600
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From: Cape Coral, Florida
UPDATE
Swapped PLUG WIRE ONLY from cylinder 4 (cool one) over to cylinder 3 and repeated process.
RESULTS
Cylinder number 4 stayed cooler and DID NOT SWAP to cylinder 3.
SUMMATION
BAD PLUG
I will buy a couple tomorrow at Autozone and replace and see how it goes. I may replace all 8 as a precaution or do you guys think that is not necessary. The plugs only have about 1500 normal street and highway driving on them. So should I replace all 8 or just buy 1 or 2 just in case?
Also, I am running AC DELCO and should I stick with them or can you suggest something better to increase performance and reduce fouling or this happening again. I usually use E3 but any suggestions?
Naturally Aspirated but has CAI and LG Long Tube Headers, no CATS and OFFROAD X-Pipe and a tune.
Thanks and fingers crossed this fixes it...
Swapped PLUG WIRE ONLY from cylinder 4 (cool one) over to cylinder 3 and repeated process.
RESULTS
Cylinder number 4 stayed cooler and DID NOT SWAP to cylinder 3.
SUMMATION
BAD PLUG
I will buy a couple tomorrow at Autozone and replace and see how it goes. I may replace all 8 as a precaution or do you guys think that is not necessary. The plugs only have about 1500 normal street and highway driving on them. So should I replace all 8 or just buy 1 or 2 just in case?
Also, I am running AC DELCO and should I stick with them or can you suggest something better to increase performance and reduce fouling or this happening again. I usually use E3 but any suggestions?
Naturally Aspirated but has CAI and LG Long Tube Headers, no CATS and OFFROAD X-Pipe and a tune.
Thanks and fingers crossed this fixes it...
Thread Starter
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From: Gray Tennessee
I have read a lot about people saying the NGK are the best. I can't say I am very happy with the AC Delco crapping out on me so soon. I mean less than 1500 miles, thats pretty crappy.
Trying to find out which NGK is best, the OEM Gap is .040 so need to know which NGK and what gap. I have seen gaps from .040 to .060 so I want the best options.
Trying to find out which NGK is best, the OEM Gap is .040 so need to know which NGK and what gap. I have seen gaps from .040 to .060 so I want the best options.
