P0300 after top end run e force '06 LS7
11-28-2015, 10:16 AM
#1
Drifting
Thread Starter
P0300 after top end run e force '06 LS7
Not looking good.
After (during) WOT run to the middle of 5th gear yesterday there was stumble then the engine light. Shifted at 4K rpm in third since it was cold out and on a curve, shifted out of 4th at close to but well under redline then WOT in fifth till about 5000 RPM. Felt a little stumble but it went away quickly so I stayed in it....
Nothing out of the ordinary...until...
Check engine, rough running, oil stench.
The tech 2 that I am just beginning to learn to use has clearly shown me repeated misfire in cylinder number 5.
I do have a good amount of formal tech training and hands on but old school stuff. Can understand anything if it is explained so if anyone has some advice please fill me in. I do also have factory service manuals.
Seems I am rusty for sure.
There are a few misfires in history but not now (maybe between 20 to 40 times) on neighboring cylinders 3 and 7 but since then those are running and no longer misfiring. Maybe these cylinders on that bank became lean during my run.
The motor is quiet and seems smooth (no knocks or rattles) except for running on 7cyls.
Questions:
* Wonder why I have a random misfire code P0300 instead of the computer identifying cylinder number 5? The scanner clearly shows number 5 has like 40K misfires and continues to do so.
This makes me worry that it is mechanical, not electrical like a plug or wire. Maybe the computer cant identify low compression in one particular cylinder. But then how does it know that #5 is missing? I suppose that crank speed changes at that point each rpm?
*Shouldn't the 02 sensors vary greatly from bank to bank if one side has a dead cylinder? (the values change so much, so rapidly it is hard to read this)
Definitely see how a wide band 02 sensor is a must for mechanically minded dudes and DIY tuners. If anyone can tell me how to use the oem 02 sensor data I'd appreciate it.
* Does the computer do anything to individual injectors or fuel if there is continual misfire in one cylinder or does it just let fuel wash into the dead cylinder?
I drove the car back about 10 miles from the time of the check engine light then restarted to make sure the code is accurate.
At night no arcing from the wire. (that would have been a relief). Again, if electrical maybe the cylinder would cut in and out...not just be dead.
Going to check compression in a little while.
* is there a special adapter for the LS7 plug hole or can i just buy a good compression test kit?
On top of all this there is the stench of burning oil, slight smoke coming from under the eforce on the drivers side. I first though it was head gasket but looks like a valve cover gasket is squished out on the inside rail. Unlikely coincidence that both happen same time but this is the first time I really got on the car.
I have put about 3k miles on the eforce setup and about 600 miles since decreasing pulley size and tune. Making about 685 peak rwhp when all is good.
Just figured I would post this and maybe someone can relate their experience or I can help someone else out once I find the issue.
I want to add that this is not the fault of Edelbrock or GM. The oem tune and pulley that came with the E-force kit likely would never have this issue.
This is another reason why I should have tuning software. I could have seen if and when the engine was experiencing detonation or pulling timing before I went out and pushed it's limits. Maybe avoided this whole thing. Just because I went to a good tuner and ran the car on dyno doesnt mean I should not check and see how things look.
Going to work on it. (would rather be driving).
After (during) WOT run to the middle of 5th gear yesterday there was stumble then the engine light. Shifted at 4K rpm in third since it was cold out and on a curve, shifted out of 4th at close to but well under redline then WOT in fifth till about 5000 RPM. Felt a little stumble but it went away quickly so I stayed in it....
Nothing out of the ordinary...until...
Check engine, rough running, oil stench.
The tech 2 that I am just beginning to learn to use has clearly shown me repeated misfire in cylinder number 5.
I do have a good amount of formal tech training and hands on but old school stuff. Can understand anything if it is explained so if anyone has some advice please fill me in. I do also have factory service manuals.
Seems I am rusty for sure.
There are a few misfires in history but not now (maybe between 20 to 40 times) on neighboring cylinders 3 and 7 but since then those are running and no longer misfiring. Maybe these cylinders on that bank became lean during my run.
The motor is quiet and seems smooth (no knocks or rattles) except for running on 7cyls.
Questions:
* Wonder why I have a random misfire code P0300 instead of the computer identifying cylinder number 5? The scanner clearly shows number 5 has like 40K misfires and continues to do so.
This makes me worry that it is mechanical, not electrical like a plug or wire. Maybe the computer cant identify low compression in one particular cylinder. But then how does it know that #5 is missing? I suppose that crank speed changes at that point each rpm?
*Shouldn't the 02 sensors vary greatly from bank to bank if one side has a dead cylinder? (the values change so much, so rapidly it is hard to read this)
Definitely see how a wide band 02 sensor is a must for mechanically minded dudes and DIY tuners. If anyone can tell me how to use the oem 02 sensor data I'd appreciate it.
* Does the computer do anything to individual injectors or fuel if there is continual misfire in one cylinder or does it just let fuel wash into the dead cylinder?
I drove the car back about 10 miles from the time of the check engine light then restarted to make sure the code is accurate.
At night no arcing from the wire. (that would have been a relief). Again, if electrical maybe the cylinder would cut in and out...not just be dead.
Going to check compression in a little while.
* is there a special adapter for the LS7 plug hole or can i just buy a good compression test kit?
On top of all this there is the stench of burning oil, slight smoke coming from under the eforce on the drivers side. I first though it was head gasket but looks like a valve cover gasket is squished out on the inside rail. Unlikely coincidence that both happen same time but this is the first time I really got on the car.
I have put about 3k miles on the eforce setup and about 600 miles since decreasing pulley size and tune. Making about 685 peak rwhp when all is good.
Just figured I would post this and maybe someone can relate their experience or I can help someone else out once I find the issue.
I want to add that this is not the fault of Edelbrock or GM. The oem tune and pulley that came with the E-force kit likely would never have this issue.
This is another reason why I should have tuning software. I could have seen if and when the engine was experiencing detonation or pulling timing before I went out and pushed it's limits. Maybe avoided this whole thing. Just because I went to a good tuner and ran the car on dyno doesnt mean I should not check and see how things look.
Going to work on it. (would rather be driving).
11-28-2015, 11:05 PM
#2
Race Director
Member Since: May 2004
Location: Raleigh, NC
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St. Jude Donor '15
Not looking good.
After (during) WOT run to the middle of 5th gear yesterday there was stumble then the engine light. Shifted at 4K rpm in third since it was cold out and on a curve, shifted out of 4th at close to but well under redline then WOT in fifth till about 5000 RPM. Felt a little stumble but it went away quickly so I stayed in it....
Nothing out of the ordinary...until...
Check engine, rough running, oil stench.
The tech 2 that I am just beginning to learn to use has clearly shown me repeated misfire in cylinder number 5.
I do have a good amount of formal tech training and hands on but old school stuff. Can understand anything if it is explained so if anyone has some advice please fill me in. I do also have factory service manuals.
Seems I am rusty for sure.
There are a few misfires in history but not now (maybe between 20 to 40 times) on neighboring cylinders 3 and 7 but since then those are running and no longer misfiring. Maybe these cylinders on that bank became lean during my run.
The motor is quiet and seems smooth (no knocks or rattles) except for running on 7cyls.
Questions:
* Wonder why I have a random misfire code P0300 instead of the computer identifying cylinder number 5? The scanner clearly shows number 5 has like 40K misfires and continues to do so.
This makes me worry that it is mechanical, not electrical like a plug or wire. Maybe the computer cant identify low compression in one particular cylinder. But then how does it know that #5 is missing? I suppose that crank speed changes at that point each rpm?
Yes it can tell by when the crank speed changes.. seems crazy, but it can
*Shouldn't the 02 sensors vary greatly from bank to bank if one side has a dead cylinder? (the values change so much, so rapidly it is hard to read this)
Definitely see how a wide band 02 sensor is a must for mechanically minded dudes and DIY tuners. If anyone can tell me how to use the oem 02 sensor data I'd appreciate it.
narrowband O2's can react fast enough to see a misfire, but I highly doubt you'll see it on a scanner. You'd need something like HP Tuners to graph the O2 data during a run to really be able to see it. The stock O2 sensors are useless for anything other than cruising around. They'll cycle up and down.. that's about it.. need a wideband for really seeing what's going on
* Does the computer do anything to individual injectors or fuel if there is continual misfire in one cylinder or does it just let fuel wash into the dead cylinder?
Yes it will cut fuel to that cylinder if it thinks it's dead to make sure the cats don't get soaked with fuel
I drove the car back about 10 miles from the time of the check engine light then restarted to make sure the code is accurate.
At night no arcing from the wire. (that would have been a relief). Again, if electrical maybe the cylinder would cut in and out...not just be dead.
Going to check compression in a little while.
* is there a special adapter for the LS7 plug hole or can i just buy a good compression test kit?
No, same plug size as every other LS engine out there
On top of all this there is the stench of burning oil, slight smoke coming from under the eforce on the drivers side. I first though it was head gasket but looks like a valve cover gasket is squished out on the inside rail. Unlikely coincidence that both happen same time but this is the first time I really got on the car.
I have put about 3k miles on the eforce setup and about 600 miles since decreasing pulley size and tune. Making about 685 peak rwhp when all is good.
Just figured I would post this and maybe someone can relate their experience or I can help someone else out once I find the issue.
I want to add that this is not the fault of Edelbrock or GM. The oem tune and pulley that came with the E-force kit likely would never have this issue.
This is another reason why I should have tuning software. I could have seen if and when the engine was experiencing detonation or pulling timing before I went out and pushed it's limits. Maybe avoided this whole thing. Just because I went to a good tuner and ran the car on dyno doesnt mean I should not check and see how things look.
Going to work on it. (would rather be driving).
After (during) WOT run to the middle of 5th gear yesterday there was stumble then the engine light. Shifted at 4K rpm in third since it was cold out and on a curve, shifted out of 4th at close to but well under redline then WOT in fifth till about 5000 RPM. Felt a little stumble but it went away quickly so I stayed in it....
Nothing out of the ordinary...until...
Check engine, rough running, oil stench.
The tech 2 that I am just beginning to learn to use has clearly shown me repeated misfire in cylinder number 5.
I do have a good amount of formal tech training and hands on but old school stuff. Can understand anything if it is explained so if anyone has some advice please fill me in. I do also have factory service manuals.
Seems I am rusty for sure.
There are a few misfires in history but not now (maybe between 20 to 40 times) on neighboring cylinders 3 and 7 but since then those are running and no longer misfiring. Maybe these cylinders on that bank became lean during my run.
The motor is quiet and seems smooth (no knocks or rattles) except for running on 7cyls.
Questions:
* Wonder why I have a random misfire code P0300 instead of the computer identifying cylinder number 5? The scanner clearly shows number 5 has like 40K misfires and continues to do so.
This makes me worry that it is mechanical, not electrical like a plug or wire. Maybe the computer cant identify low compression in one particular cylinder. But then how does it know that #5 is missing? I suppose that crank speed changes at that point each rpm?
Yes it can tell by when the crank speed changes.. seems crazy, but it can
*Shouldn't the 02 sensors vary greatly from bank to bank if one side has a dead cylinder? (the values change so much, so rapidly it is hard to read this)
Definitely see how a wide band 02 sensor is a must for mechanically minded dudes and DIY tuners. If anyone can tell me how to use the oem 02 sensor data I'd appreciate it.
narrowband O2's can react fast enough to see a misfire, but I highly doubt you'll see it on a scanner. You'd need something like HP Tuners to graph the O2 data during a run to really be able to see it. The stock O2 sensors are useless for anything other than cruising around. They'll cycle up and down.. that's about it.. need a wideband for really seeing what's going on
* Does the computer do anything to individual injectors or fuel if there is continual misfire in one cylinder or does it just let fuel wash into the dead cylinder?
Yes it will cut fuel to that cylinder if it thinks it's dead to make sure the cats don't get soaked with fuel
I drove the car back about 10 miles from the time of the check engine light then restarted to make sure the code is accurate.
At night no arcing from the wire. (that would have been a relief). Again, if electrical maybe the cylinder would cut in and out...not just be dead.
Going to check compression in a little while.
* is there a special adapter for the LS7 plug hole or can i just buy a good compression test kit?
No, same plug size as every other LS engine out there
On top of all this there is the stench of burning oil, slight smoke coming from under the eforce on the drivers side. I first though it was head gasket but looks like a valve cover gasket is squished out on the inside rail. Unlikely coincidence that both happen same time but this is the first time I really got on the car.
I have put about 3k miles on the eforce setup and about 600 miles since decreasing pulley size and tune. Making about 685 peak rwhp when all is good.
Just figured I would post this and maybe someone can relate their experience or I can help someone else out once I find the issue.
I want to add that this is not the fault of Edelbrock or GM. The oem tune and pulley that came with the E-force kit likely would never have this issue.
This is another reason why I should have tuning software. I could have seen if and when the engine was experiencing detonation or pulling timing before I went out and pushed it's limits. Maybe avoided this whole thing. Just because I went to a good tuner and ran the car on dyno doesnt mean I should not check and see how things look.
Going to work on it. (would rather be driving).
Yes, having HP Tuners and a wideband is invaluable IMO.
I run Dash Logic also so I can get warnings for knock, AFR being way off, etc.
11-29-2015, 10:29 PM
#3
Le Mans Master
Member Since: Aug 2005
Location: CA.
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St. Jude Donor '13-'14-'15
There is NO independent cylinder misfire code on your car---Just a "random misfire" code in general----- could be any one cylinder or several
If you are sure the misfire is in fact real then you have one---( often an underdrive pulley will create a "false misfire" as do other mods)
YES the bank with the misfire should have a RICHER 02 voltage average (higher than the other side) OR have a negative fuel trim as the ECM is attempting to correct the P/T fuel thinking it is overly rich--
Most often cause for a misfire is ignition related---A plug that has been dropped and bent closed or a wire that was not "snapped" properly onto the coil
It is rare to have a lean fuel misfire on a bolt on engine---especially on one cylinder--Most likely it would be lean everywhere and ping like crazy --have no power--overheat--
A broken valve spring is the 2nd most common cause for a misfire--Did you work on the valve train??----
YES a wideband would show which bank has the misfire by reading a richer AFR on that side---BUT it won't tell you the cause of the misfire------
If you are sure the misfire is in fact real then you have one---( often an underdrive pulley will create a "false misfire" as do other mods)
YES the bank with the misfire should have a RICHER 02 voltage average (higher than the other side) OR have a negative fuel trim as the ECM is attempting to correct the P/T fuel thinking it is overly rich--
Most often cause for a misfire is ignition related---A plug that has been dropped and bent closed or a wire that was not "snapped" properly onto the coil
It is rare to have a lean fuel misfire on a bolt on engine---especially on one cylinder--Most likely it would be lean everywhere and ping like crazy --have no power--overheat--
A broken valve spring is the 2nd most common cause for a misfire--Did you work on the valve train??----
YES a wideband would show which bank has the misfire by reading a richer AFR on that side---BUT it won't tell you the cause of the misfire------
11-30-2015, 05:20 PM
#5
Drifting
Member Since: Jul 2011
Location: Boca Raton Florida
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I agree that most misfires are ignition related and as simple as bad plug with cracked insulator, bad wire or last but not least a bad coil (this i suspect very much, weak coil failing under load) i would eliminate all those before worrying about a mechanical problem. I am almost willing to bet that it is that simple. You seem to know quite a bit, i bet you know how test those components.