P0300: Random Cylinder Misfire Detected
11-26-2007, 10:29 PM
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P0300: Random Cylinder Misfire Detected OK, so I am driving the car around and I finally get a Service Engine Soon light.. so I drive to Advance Discount Auto Parts, and run the codereader, and I get code P0300: Random Cylinder Misfire Detected....
I tried unplugging the spark plugs one at a time to see if there was any variation, and it seems as if the driver side coil packs are getting less power than the passenger side coil packs. Furthermore, sometimes I'll be driving the car and the car will feel as if 1 or more cylinderrs is totally dead, and other times it runs just fine, but I have never seen the miss go away at idle... Also, if the passenger side of the car gets wet, the car will miss for about 30 seconds until the water has evaporated.
I recently degreased my engine bay, and then put in brand new plugs/wires in it. Even before the new plugs/wires, the miss was present.
So, the question lies..... where do I begin? What do I replace?
Any help would be greatly appreciated....
Dana Shaw
I tried unplugging the spark plugs one at a time to see if there was any variation, and it seems as if the driver side coil packs are getting less power than the passenger side coil packs. Furthermore, sometimes I'll be driving the car and the car will feel as if 1 or more cylinderrs is totally dead, and other times it runs just fine, but I have never seen the miss go away at idle... Also, if the passenger side of the car gets wet, the car will miss for about 30 seconds until the water has evaporated.
I recently degreased my engine bay, and then put in brand new plugs/wires in it. Even before the new plugs/wires, the miss was present.
So, the question lies..... where do I begin? What do I replace?
Any help would be greatly appreciated....
Dana Shaw
11-27-2007, 06:13 AM
#2
The simplest thing to do is find someone with a scan tool such as a Tech2 that shows the misfire counts on each cylinder. The cylinder with the highest misfires is the starting cylinder to look at. If the car has been tuned for a cam, the misfires may be off, but since the P0300 is setting, I am guessing it is working. Hope this helps.
Mike Norris
Mike Norris
11-27-2007, 08:53 AM
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i agree with mike, a tech is a great tool for daig these kinds of problems. i am a tech at chevy and could look at it for you but i think your kind far away
11-27-2007, 03:54 PM
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Get your reading glasses on. This is straight from GM.
DTC P0300 Engine Misfire Detected
Circuit Description
The Crankshaft Position sensor is mounted through the side of the engine block at the rear of Bank 2 behind the starter assembly. The Crankshaft Position sensor works in conjunction with a 24X reluctor wheel on the crankshaft. The reluctor wheel is inside the engine immediately in front of the rear main bearing. The PCM provides a 12 volt power supply to the CKP sensor as well as a ground and a signal circuit.
A misfire causes a change in crankshaft speed. The PCM times the interval between each pulse and compares each new time interval with the previous one in order to determine when an excessive change in crankshaft speed has occurred. You can expect a certain amount of acceleration/deceleration between each firing stroke, but if the crankshaft speed changes are greater than an expected amount, the PCM interprets this as a misfire.
The PCM uses the Crankshaft Position sensor for both spark and fueling. As the crankshaft rotates, the reluctor wheel teeth interrupt a magnetic field produced by a magnet within the sensor. The sensors internal circuitry detects this and produces a signal which the PCM reads. The PCM uses this 24X signal in combination with the Camshaft Position sensor 1X signal in order to accurately determine crankshaft position. The PCM also calculates a 4X signal from this information. The PCM uses the 4X signal for internal calculations. The 4X signal also provides a tach signal for any device which requires one.
Observe that as long as the PCM receives the Crankshaft Position sensor 24X signal, the engine will start. The PCM can determine top dead center for all cylinders by using the Crankshaft Position sensor 24X signal alone. The Camshaft Position sensor 1X signal is used by the PCM to determine if the cylinder at top dead center is on the firing stroke, or the exhaust stroke. The system attempts synchronization and looks for an increase in engine speed indicating the engine started. If the PCM does not detect an increase in engine speed, the PCM assumes it incorrectly synchronized to the exhaust stroke and re-syncs to the opposite cam position. A slightly longer cranking time may be a symptom of this condition.
Conditions for Running the DTC
• DTCs P0101, P0102, P0103, P0117, P0118, P0121, P0122, P0123, P0125, P0335, P0336, P0341, P0342, P0343, P0500, P0502, P0503, P1258 not set.
• The engine speed is between 450 RPM and 3,001 RPM.
• The ignition voltage is between 10.0 volts and 18 .0 volts.
• The engine coolant temperature is between -7°C (19°F) and 130°C (266°F).
• Fuel level greater than 10%
• The TP sensor angle is steady within 1%.
• The ABS and Traction Control systems are not active.
• The transmission is not changing gears.
• The AIR diagnostic test is not in progress
• The A/C clutch is not changing states.
• The PCM is not in fuel shut-off or decel fuel cut-off mode.
• The ABS signals not exceeding rough road thresholds.
Conditions for Setting the DTC
• The PCM determines that an emission type Misfire is present.
• The PCM determines that a catalyst damaging Misfire is present.
Action Taken When the DTC Sets
The PCM illuminates the Malfunction Indicator Lamp (MIL) under the following conditions:
• The PCM illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails, if the diagnostic fails under the same conditions (load, RPM, temperature, etc.) as the previous ignition cycle that the test ran and failed.
• The first time the diagnostic fails, the PCM records the operating conditions in Failure Records.
• The PCM determines the percent of misfire over a 1,000 revolution period is high enough to cause excessive tail pipe emissions. The PCM illuminates the Malfunction Indicator lamp the next consecutive ignition cycle that the diagnostic runs and fails, if the diagnostic fails under the same conditions (load, RPM, temperature, etc.) as the previous ignition cycle that the test ran and failed. Or
• The PCM flashes the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails a catalyst damaging misfire.
Conditions for Clearing the MIL/DTC
Important: If the last failure was during a non-typical driving condition, the MIL may remain ON longer than the three ignition cycles. Review the Freeze Frame/Failure Records for the last failure conditions.
• The PCM turns the MIL OFF after three consecutive ignition cycles that the diagnostic runs and does not fail within the same conditions that the DTC last failed.
• A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures.
• A last test failed (Current DTC) clears when the diagnostic runs and does not fail.
• Use a scan tool in order to clear the MIL/DTC.
Diagnostic Aids
Important:
• Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent contaminant intrusion into the PCM.
• For any test that requires probing the PCM or component harness connectors, use the Connector Test Adapter Kit J 35616 . Using this kit prevents any damage to the harness connector terminals. Refer to Using Connector Test Adapters in Wiring Systems for procedures.
• Running the vehicle out of fuel causes sufficient misfire to set DTC P0300. A vehicle that is out of fuel may have DTC P0461 also set.
• A restricted fuel filter can cause sufficient misfire to set DTC P0300. Refer to Fuel System Diagnosis .
• A misfire may not be apparent at idle. The misfire may only occur above idle under a load. Road test the vehicle and monitor the misfire current counters.
• Observe, if more then one cylinder is mis-firing, the scan tool may only display one cylinder mis-firing. This will not be apparent until the repair is completed. Also, if an ignition coil/module ground circuit is open for one side of the engine, the scan tool may only display 2 or 3 cylinders mis-firing. Inspect the ground circuit for the ignition coil/modules on the cylinder bank of the engine that has more then one cylinder mis-firing.
• Excessive vibration from sources other than the engine could cause a misfire DTC. The following are possible sources of vibration:
- Variable thickness brake rotor
- Drive shaft not balanced
- Certain rough road conditions
• Using the Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This will isolate when the DTC failed.
• For an intermittent condition, refer to Symptoms .
DTC P0300 Engine Misfire Detected
Circuit Description
The Crankshaft Position sensor is mounted through the side of the engine block at the rear of Bank 2 behind the starter assembly. The Crankshaft Position sensor works in conjunction with a 24X reluctor wheel on the crankshaft. The reluctor wheel is inside the engine immediately in front of the rear main bearing. The PCM provides a 12 volt power supply to the CKP sensor as well as a ground and a signal circuit.
A misfire causes a change in crankshaft speed. The PCM times the interval between each pulse and compares each new time interval with the previous one in order to determine when an excessive change in crankshaft speed has occurred. You can expect a certain amount of acceleration/deceleration between each firing stroke, but if the crankshaft speed changes are greater than an expected amount, the PCM interprets this as a misfire.
The PCM uses the Crankshaft Position sensor for both spark and fueling. As the crankshaft rotates, the reluctor wheel teeth interrupt a magnetic field produced by a magnet within the sensor. The sensors internal circuitry detects this and produces a signal which the PCM reads. The PCM uses this 24X signal in combination with the Camshaft Position sensor 1X signal in order to accurately determine crankshaft position. The PCM also calculates a 4X signal from this information. The PCM uses the 4X signal for internal calculations. The 4X signal also provides a tach signal for any device which requires one.
Observe that as long as the PCM receives the Crankshaft Position sensor 24X signal, the engine will start. The PCM can determine top dead center for all cylinders by using the Crankshaft Position sensor 24X signal alone. The Camshaft Position sensor 1X signal is used by the PCM to determine if the cylinder at top dead center is on the firing stroke, or the exhaust stroke. The system attempts synchronization and looks for an increase in engine speed indicating the engine started. If the PCM does not detect an increase in engine speed, the PCM assumes it incorrectly synchronized to the exhaust stroke and re-syncs to the opposite cam position. A slightly longer cranking time may be a symptom of this condition.
Conditions for Running the DTC
• DTCs P0101, P0102, P0103, P0117, P0118, P0121, P0122, P0123, P0125, P0335, P0336, P0341, P0342, P0343, P0500, P0502, P0503, P1258 not set.
• The engine speed is between 450 RPM and 3,001 RPM.
• The ignition voltage is between 10.0 volts and 18 .0 volts.
• The engine coolant temperature is between -7°C (19°F) and 130°C (266°F).
• Fuel level greater than 10%
• The TP sensor angle is steady within 1%.
• The ABS and Traction Control systems are not active.
• The transmission is not changing gears.
• The AIR diagnostic test is not in progress
• The A/C clutch is not changing states.
• The PCM is not in fuel shut-off or decel fuel cut-off mode.
• The ABS signals not exceeding rough road thresholds.
Conditions for Setting the DTC
• The PCM determines that an emission type Misfire is present.
• The PCM determines that a catalyst damaging Misfire is present.
Action Taken When the DTC Sets
The PCM illuminates the Malfunction Indicator Lamp (MIL) under the following conditions:
• The PCM illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails, if the diagnostic fails under the same conditions (load, RPM, temperature, etc.) as the previous ignition cycle that the test ran and failed.
• The first time the diagnostic fails, the PCM records the operating conditions in Failure Records.
• The PCM determines the percent of misfire over a 1,000 revolution period is high enough to cause excessive tail pipe emissions. The PCM illuminates the Malfunction Indicator lamp the next consecutive ignition cycle that the diagnostic runs and fails, if the diagnostic fails under the same conditions (load, RPM, temperature, etc.) as the previous ignition cycle that the test ran and failed. Or
• The PCM flashes the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails a catalyst damaging misfire.
Conditions for Clearing the MIL/DTC
Important: If the last failure was during a non-typical driving condition, the MIL may remain ON longer than the three ignition cycles. Review the Freeze Frame/Failure Records for the last failure conditions.
• The PCM turns the MIL OFF after three consecutive ignition cycles that the diagnostic runs and does not fail within the same conditions that the DTC last failed.
• A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures.
• A last test failed (Current DTC) clears when the diagnostic runs and does not fail.
• Use a scan tool in order to clear the MIL/DTC.
Diagnostic Aids
Important:
• Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent contaminant intrusion into the PCM.
• For any test that requires probing the PCM or component harness connectors, use the Connector Test Adapter Kit J 35616 . Using this kit prevents any damage to the harness connector terminals. Refer to Using Connector Test Adapters in Wiring Systems for procedures.
• Running the vehicle out of fuel causes sufficient misfire to set DTC P0300. A vehicle that is out of fuel may have DTC P0461 also set.
• A restricted fuel filter can cause sufficient misfire to set DTC P0300. Refer to Fuel System Diagnosis .
• A misfire may not be apparent at idle. The misfire may only occur above idle under a load. Road test the vehicle and monitor the misfire current counters.
• Observe, if more then one cylinder is mis-firing, the scan tool may only display one cylinder mis-firing. This will not be apparent until the repair is completed. Also, if an ignition coil/module ground circuit is open for one side of the engine, the scan tool may only display 2 or 3 cylinders mis-firing. Inspect the ground circuit for the ignition coil/modules on the cylinder bank of the engine that has more then one cylinder mis-firing.
• Excessive vibration from sources other than the engine could cause a misfire DTC. The following are possible sources of vibration:
- Variable thickness brake rotor
- Drive shaft not balanced
- Certain rough road conditions
• Using the Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This will isolate when the DTC failed.
• For an intermittent condition, refer to Symptoms .
11-27-2007, 04:51 PM
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I used to get a code like that one when i had my Lt1 car...i had long tubes and used the wires to extend the O2's...anytime it rained hard you could bet that it'd be missing really bad with that code..everytime it was the O2s ...the connections got wet and i guess shorted giveing the computer a crazy signal...then causing a serve rich condition fouling the O2s..I would ethier take them out and wire brush them or buy new ones...
It stopped the day i put the extensions on with the weather pack connections
It stopped the day i put the extensions on with the weather pack connections
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11-28-2007, 09:42 AM
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I actually figured it out.....
Thanks to Robert (MRR23), I found out it was the Bank 2 sensor 1 O2 sensor that was out. That meant that the car thought it was extremely lean, so the car was throwing WAAAAYYY too much fuel at the right side cylinders, causing the spark to burn out, which caused the misfire.
Thanks to Robert (MRR23), I found out it was the Bank 2 sensor 1 O2 sensor that was out. That meant that the car thought it was extremely lean, so the car was throwing WAAAAYYY too much fuel at the right side cylinders, causing the spark to burn out, which caused the misfire.
11-28-2007, 04:53 PM
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it did set the code for it.
had the following codes when i scanned it last night:
P0151 o2 bank 2 sensor 1
P0175 fuel trim rich bank 2
P0300 random misfire
P0351 coil #1 control circuit
had the following codes when i scanned it last night:
P0151 o2 bank 2 sensor 1
P0175 fuel trim rich bank 2
P0300 random misfire
P0351 coil #1 control circuit
11-28-2007, 10:56 PM
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Question is whether the misfiring jacked the O2 sensor output
with all the "unburnt air", or whether the O2 bad caused the
misfiring. Water can bother O2 sensors. Water can bother
plug wires and coils. Use dielectric grease on both ends of the
new wires.
HPTuners will let you log Misfire Current Cylinder (1-8) and
see rolling misfire counts. P0300 means it can't pin it down to
any one cylinder, otherwise you'd get P0301 - P0308.
with all the "unburnt air", or whether the O2 bad caused the
misfiring. Water can bother O2 sensors. Water can bother
plug wires and coils. Use dielectric grease on both ends of the
new wires.
HPTuners will let you log Misfire Current Cylinder (1-8) and
see rolling misfire counts. P0300 means it can't pin it down to
any one cylinder, otherwise you'd get P0301 - P0308.
11-08-2015, 06:09 PM
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Installed stock 243s and a TV2 cam recently and got it tuned. I hit serious traffic on the way home and threw a SES light after about 2 hours of stop and go traffic. My car ran fine with ~56,000 miles before. Wouldn't the tuner have adjusted for this? Couldn't the trip home messed something up? I checked the plug wire connections and everything seems fine.
At WOT, the car will slightly sputter through gears so I know something is up. The tuner did say there was knock detection due to my true duals moving and hitting something but that's about it.
At WOT, the car will slightly sputter through gears so I know something is up. The tuner did say there was knock detection due to my true duals moving and hitting something but that's about it.
11-08-2015, 06:18 PM
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A little more to the story: Vacuum lines seem fine too btw. I sprayed brake clean with the engine running and experienced no rpm change. The engine wasn't at operating temp though. Does that matter? I do hear a faint intermittent whistle from the passenger side engine bay while driving down the highway. Maybe the PVC is leaking? I took out the "Y" connection from the old perimeter bolt valve cover and ran a single line to one of the bungs on the passenger center bolt valve cover.
How do I test the coil packs? I also smell gas pretty strong at idle, but I do have true duals that dump just past the axles so that's expected. I've seen a few folks mention injectors being stuck open. How can I troubleshoot that as well?
How do I test the coil packs? I also smell gas pretty strong at idle, but I do have true duals that dump just past the axles so that's expected. I've seen a few folks mention injectors being stuck open. How can I troubleshoot that as well?
