P03xx misfires include preignition?
09-18-2014, 03:25 AM
#1
P03xx misfires include preignition? Hey, guys.
Can someone tell me if the P030x series of codes (in a stock LS1) is confined to only indicating a loss of combustion or if it could include preignition as well? In other words, do these codes solely indicate the loss of combustion in general or if it is set off by a lack of combustion specifically at top dead center moment regardless of whether or not the air-fuel mixture is ever ignited?
Also, when preignition occurs, must there always be a pinging sound? And just how does preignition cause that sound? Is it the valves clattering as a result of the explosion happening before they have a chance to fully close?
Finally, are the O2 sensors designated to specific cylinders or do they rotate between cylinders? Is there a particular O2 sensor that controls cylinder 5, and if so, which one is it?
Any info is much appreciated.
Can someone tell me if the P030x series of codes (in a stock LS1) is confined to only indicating a loss of combustion or if it could include preignition as well? In other words, do these codes solely indicate the loss of combustion in general or if it is set off by a lack of combustion specifically at top dead center moment regardless of whether or not the air-fuel mixture is ever ignited?
Also, when preignition occurs, must there always be a pinging sound? And just how does preignition cause that sound? Is it the valves clattering as a result of the explosion happening before they have a chance to fully close?
Finally, are the O2 sensors designated to specific cylinders or do they rotate between cylinders? Is there a particular O2 sensor that controls cylinder 5, and if so, which one is it?
Any info is much appreciated.
09-21-2014, 02:37 PM
#2
The knocking/pinging sound is usually the piston rocking in the bore. Air/fuel mixture should burn, not explode..and preignition/detonation/etc. are cases where you don't get a good, complete, well-timed burn of the mixture. I don't know exactly what the logic is in the computer but hopefully some of the more knowledgeable guys can tell us that. There are knock sensors that detect the sound/vibration of knock and similar. But misfires can be logged just from a bad plug or plug wire.
In F-body cars, you will likely have 4 O2 sensors. Two before the catalytic converters and two after. The "fore" sensors are actually used to see how the engine is running. You have one for each side of the exhaust, and each side of the exhaust serves 4 cylinders(your motor has two banks of 4 cylinders; 4 on the left, 4 on the right if a V8). So each of the fore O2 sensors corresponds to one bank of 4 cyls. The "aft" O2 sensors are there to monitor the health/function of your cats.
In F-body cars, you will likely have 4 O2 sensors. Two before the catalytic converters and two after. The "fore" sensors are actually used to see how the engine is running. You have one for each side of the exhaust, and each side of the exhaust serves 4 cylinders(your motor has two banks of 4 cylinders; 4 on the left, 4 on the right if a V8). So each of the fore O2 sensors corresponds to one bank of 4 cyls. The "aft" O2 sensors are there to monitor the health/function of your cats.
Last edited by Mercier; 09-22-2014 at 12:12 AM.
09-22-2014, 03:02 AM
#3
Mercier,
Thank you very much for clarifying.
When three of my O2 sensors (1 fore, and two rear) were fowled by a lubricant spray, I had gotten severe misfiring. Their malfunctioning status was confirmed by a scanner. When those sensors were replaced, it got much better, but there's still a little misfiring. Altogether, I have gotten the P0305 code, which then switched to P0300, but after resetting the codes, the P0305 returned after an unusually long delay (I experienced mild misfires while driving throughout the entire time). After several hundred miles, the P0305 has remained, with the only thing changing being the appearance and disappearing of the pending for P0305. I suspect the remaining (driver side fore) sensor is also malfunctioning, but I haven't gotten it scanned yet, so I thought I'd check to see the liklihood of a fore sensor affecting only one cylinder, which of course is not likely unless there's some other factor affecting that cylinder.
Would you recommend that I replace the remaining sensor to start with or is there another procedure worth carrying out first?
Thank you very much for clarifying.
When three of my O2 sensors (1 fore, and two rear) were fowled by a lubricant spray, I had gotten severe misfiring. Their malfunctioning status was confirmed by a scanner. When those sensors were replaced, it got much better, but there's still a little misfiring. Altogether, I have gotten the P0305 code, which then switched to P0300, but after resetting the codes, the P0305 returned after an unusually long delay (I experienced mild misfires while driving throughout the entire time). After several hundred miles, the P0305 has remained, with the only thing changing being the appearance and disappearing of the pending for P0305. I suspect the remaining (driver side fore) sensor is also malfunctioning, but I haven't gotten it scanned yet, so I thought I'd check to see the liklihood of a fore sensor affecting only one cylinder, which of course is not likely unless there's some other factor affecting that cylinder.
Would you recommend that I replace the remaining sensor to start with or is there another procedure worth carrying out first?
09-22-2014, 11:14 AM
#4
If you replaced the other three and you plan on keeping the car, replace that one. You'll spend more time worrying about it than the time and money to replace it is worth. And then you have all new.
Have you pulled the #5 plug and looked at it compared to the others? If it doesn't look any different, try moving that plug and wire to the cyl. next to it, clear the code, and see if it comes back on #5. Could be an injector too but that's a little more involved.
It could still be somewhat related to O2 sensor or similar..not all intake ports are created equal. Often the far corners can starve a bit because of the design and if another sensor is causing some funny business it can get worse and cause misfire. I assume that #5 is the first cyl on the driver side if looking from the hood of the vehicle?
Also have you cleaned your MAF real good with proper electronics cleaner or MAF cleaner? They sell this at the parts stores. Usually I don't get a code for dirty MAF..but you get all kinds of funny stuff going on because the MAF gives a false reading when dirty. The little electrical elements in the middle behind the screen is what you need to clean.
More clarification from earlier - you only have two knock sensors and they are in the middle of the motor so those can't tell you one cyl from the next..or even one bank to the next I **think since they aren't off to one side or the other.
Have you pulled the #5 plug and looked at it compared to the others? If it doesn't look any different, try moving that plug and wire to the cyl. next to it, clear the code, and see if it comes back on #5. Could be an injector too but that's a little more involved.
It could still be somewhat related to O2 sensor or similar..not all intake ports are created equal. Often the far corners can starve a bit because of the design and if another sensor is causing some funny business it can get worse and cause misfire. I assume that #5 is the first cyl on the driver side if looking from the hood of the vehicle?
Also have you cleaned your MAF real good with proper electronics cleaner or MAF cleaner? They sell this at the parts stores. Usually I don't get a code for dirty MAF..but you get all kinds of funny stuff going on because the MAF gives a false reading when dirty. The little electrical elements in the middle behind the screen is what you need to clean.
More clarification from earlier - you only have two knock sensors and they are in the middle of the motor so those can't tell you one cyl from the next..or even one bank to the next I **think since they aren't off to one side or the other.
Last edited by Mercier; 09-24-2014 at 09:44 AM.