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    Thread: Multiple Misfire P0300

    1. #1
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      Multiple Misfire P0300

      Hey again,

      My Aveo - 2004 LS Manual, 134XXX KM, I have it parked while I troubleshoot a P0300.

      A friend lent me a bluetooth OBD2 interface dongle, and I've been goofing around with Torque and my android tablet. You have to turn on some extra PID's but for $5 it's been very informative.

      So far in order to correct the issue I have replaced the valve cover gasket, the plugs, and the wires.

      YES it really needed to done. The wires I pulled out were covered in oil.

      Yet the problem persists. What would have caused the gasket to fail in the first place? It's a common problem, I'm sure people have looked into that already.

      [LETS do some research, then replace this line with some relevant data]

      Anyhow, according to Torque - Cylinder 2 and 3 are misfiring badly. Misfire history is very high, and I didn't collect get any misfires from 1 and 4 in my brief drive. Also the car only misfires under load. I can't get it to misfire on idle - no matter how hard I rev this thing. I think if this was a coil it would be equally bad at idle.

      There is also a relationship where 2 and 3 misfire right after each other, when they misfire, but the occurrence is random to me as of yet.

      http://www.aveoforum.com/forum/f108/...61/index3.html

      I think tomorrow, I need to pull the plugs from two and three and check on that gasket.



    2. #2
      Aveo Whisperer 06T200's Avatar
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      I would suspect the coil, just due to the misfire under load only. If the plugs and wires are ok, not much else it can be? You can always try the water spray test to see if it acts up with moisture if you are unable to place a load on the engine. The ignition system usually acts up when under a load only as this is when cylinder pressures are higher and harder to fire the plug under load. I would say you are very close.

    3. The Following User Says Thank You to 06T200 For This Useful Post:

      Stevezilla (05-18-2016)

    4. #3
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      I replaced the coil - the resistances seemed off.

      Who was asking about the resistances on the coil?


      Well a new one is measured 6.3 - 6.5 * 2000 ohms and the old one measured 5.2 * 2000 ohms.

      I looked around at the auto-wreckers, looking at Optras - all of six of which had bad valve cover seals. - I measured the resistances, and it was a common theme. 1 and 4 Gaps measured differently than 2 and 3

      The were usually off by a thousand Ohms or so.

      They all measured between 10,000 ohms and 11,000 ohms with a difference an average difference of 1000 ohms between the two sets of ports.
      Last edited by Stevezilla; 05-18-2016 at 04:20 AM. Reason: cleanup - clarification

    5. #4
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      i bought all kinds of fancy gauges over the weekend,

      So Compression - 160 PSI just cranking three jumps of the compression tester.
      This is even across all cylinders give or take 3. I didn't leave the tester connected over time.

      Vacuum is not looking good at all... Vacuum gauge is just in the RED - 16 through 18 Units depending on engine temperature.

      (The ECU according to torque seems to think I'm running ~21.5) So that tells me I need to test timing? What else could I test?

      I took the timing belt cover off, rolled the car to position the cams. - I got the dots to align at the top.... But what about the gear on the bottom. - The one that's connected to the pistons - how do I know if that's where it's supposed to be?

      To me the belt looks new.

      I noticed a broken bolt between the engine cradle and the motor mount while removing the air-box.

      I checked the fuel pressure as well.
      55 PSI just priming - engine off.
      58 PSI with the engine running.
      58 PSI with the engine revving.
      55 PSI with the engine off.

      In 5 minutes it looses about 1 or 2 psi after the engine is turned off.

      So I have new plugs, wires, and a coil, 58 PSI fuel pressure while running.
      Vacuum pressure is low, it should be 20 correct?
      Damn...

      P0300 Keeps coming back. Flashing on the dash.

      I'm sitting in this car imagining driving it... One day stevie boy - one day.
      Last edited by Stevezilla; 05-18-2016 at 04:43 AM. Reason: clarity - purpose - statement of fact

    6. #5
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      Fuel pressure should not be dropping either.
      -Check O-Rings
      -Check Regulator

      So the fuel pressure - should not be that high correct?
      Do these cars have regulators?
      I thought this was a regulator

      Do these cars have a fuel -regulator, that certainly looks like one kiddy corner to the fuel rail and intake manifold.
      I pulled the vacuum plug on that with the gauge attached. - And the engine running.
      there was no impact what so-ever - and the tube tore while doing this test, and for time it's taped back on. I know I have vacuum from this line....
      You know what, I don't know how much, that would be good to know.
      If the regulator does not have vacuum the fuel pressure increases, is that correct?

    7. #6
      Aveo Whisperer 06T200's Avatar
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      [QUOTE=Stevezilla;199061]

      Flashing on the dash.[QUOTE]


      As in hold light flashing??? - So ONLY the p0300. I will get on my TIS terminal and do some digging, it should have a diag flow chart to check stuff.

      Is your scannertool able to capture the O2 sensor/etc readings during misfire? I went though this a couple years back on my LT, but I don't remember all the steps.
      Last edited by 06T200; 05-18-2016 at 04:12 PM. Reason: typos

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      Paste DTC P0300

      2004 Chevrolet Aveo | Aveo (VIN S) Service Manual | Document ID: 1469303
      --------------------------------------------------------------------------------
      DTC P0300
      System Description
      The engine control module (ECM) uses information from the crankshaft position (CKP) sensor and the camshaft position (CMP) sensor in order to determine when an engine misfire is occurring. By monitoring variations in the crankshaft rotation speed for each cylinder, the ECM is able to detect individual misfire events. A misfire rate that is high enough can cause overheating and damage to the 3-way catalytic converter (TWC) under certain driving conditions. The malfunction indicator lamp (MIL) will flash ON and OFF when the conditions for TWC damage are present. If the ECM detects a misfire rate sufficient to cause emission levels to exceed a predetermined value, DTC P0300 sets.
      DTC Descriptor
      This diagnostic procedure supports the following DTC:
      DTC P0300 Engine Misfire Detected
      Conditions for Running the DTC
      DTCs P0106, P0107, P0108, P0117, P0118, P0122, P0123, P0315, P0336, P0337, P0341, P0342, and P0502 are not set.
      The engine speed is between 600-6,500 RPM and steady.
      The ignition 1 voltage is between 11-16 volts.
      The engine coolant temperature (ECT) is between -7C and 120C (19F and 248F).
      The fuel level is more than 15 percent.
      The throttle angle is steady within 4 percent.
      The antilock brake system (ABS) and the traction control system (TCS), if equipped, is not active.
      The torque management is not active.
      The transmission is not changing gears.
      The A/C clutch is not changing states.
      The ECM is not in fuel shut-off or decel fuel cut-off mode.
      The ECM is not receiving a rough road signal.
      DTC P0300 runs continuously when the above conditions are met.
      Conditions for Setting the DTC
      The ECM detects a crankshaft rotation speed variation indicating a misfire sufficient to cause emission levels to exceed a predetermined value.
      Action Taken When the DTC Sets
      The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
      The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.
      Conditions for Clearing the MIL/DTC
      The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
      A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
      A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
      Clear the MIL and the DTC with a scan tool.
      Diagnostic Aids
      Excessive vibration from sources other than the engine could cause DTC P0300 to set. The following are possible sources of vibration:
      A tire or wheel that is out of round or out of balance
      Variable thickness brake rotors
      A unbalanced or damaged driveline condition
      Certain rough road conditions
      Worn or damaged accessory drive component or belt
      For an intermittent condition, refer to Intermittent Conditions .
      Test Description
      The numbers below refer to the step numbers on the diagnostic table.
      This step determines if there is a current misfire condition. The scan tool will display increasing counts in the Total Misfire Current Counter parameter if a misfire is occurring.
      If the Total Misfire Current Counter parameter is incrementing, but the engine is NOT misfiring, this could be caused by an excessive vibration from other sources than the engine.
      If the actual CKP variation values are not within the learned values, the Total Misfire Current Counter parameter may increment.
      Step
      Action
      Values
      Yes
      No

      1
      Did you perform the Diagnostic System Check - Engine Controls?
      --
      Go to Step 2
      Go to Diagnostic System Check - Engine Controls

      2
      Important: A misfire may only occur when the engine is under a load. An engine load may be necessary to verify the condition.
      Turn ON the ignition, with the engine OFF.
      Clear the DTCs with a scan tool.
      Start the engine.
      Monitor the Misfire Current Cylinder counter parameters with a scan tool.
      Are any of the Misfire Current Cylinder counters incrementing?
      --
      Go to Step 4
      Go to Step 3

      3
      Observe the Freeze Frame/Failure Records for this DTC.
      Turn the ignition OFF for 30 seconds.
      Start the engine.
      Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
      Did the DTC fail this ignition?
      --
      Go to Step 4
      Go to Diagnostic Aids

      4
      Is the engine misfiring?
      --
      Go to Step 5
      Go to Crankshaft Position System Variation Learn

      5
      Are DTCs P0201, P0202, P0203, P0204, P0315, P0336, P0337, P0351, or P0352 set?
      --
      Go to Diagnostic Trouble Code (DTC) List
      Go to Step 6

      6
      Is there an abnormal engine noise?
      --
      Go to Symptoms - Engine Mechanical in Engine Mechanical - 1.6L (L91)
      Go to Step 7

      7
      Inspect the following components:
      The vacuum hoses and seals for splits, restrictions, and improper connections--Refer to Emission Hose Routing Diagram .
      The intake manifold for vacuum leaks
      The crankcase ventilation system for vacuum leaks--Refer to Crankcase Ventilation System Inspection/Diagnosis .
      The engine control module (ECM) grounds for corrosion and loose connections--Refer to Power Distribution Schematics in Wiring Systems.
      The exhaust system for restrictions--Refer to Restricted Exhaust in Engine Exhaust.
      The fuel for contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
      Did you find and correct the condition?
      --
      Go to Step 20
      Go to Step 8

      8
      Important: An erratic or inconsistent spark is considered a no spark.
      Turn OFF the ignition.
      Disconnect the spark plug wire from the spark plug that corresponds to the Misfire Current Cylinder counter parameters that were incrementing. Refer to Spark Plug Wire Replacement .
      Install the J 26792 Spark Tester to the boot of the spark plug and a good ground.
      Start the engine.
      Does the spark jump the tester gap?
      Go to Step 10
      Go to Step 9

      9
      Remove the spark plug wire for the affected cylinders. Refer to Spark Plug Wire Replacement .
      Inspect the spark plug wire. Refer to Spark Plug Wire Inspection .
      Measure the resistance of the spark plug wire with a DMM.
      Is the spark plug wire resistance less than the specified value?
      1,000 ohms per 30 cm (per ft)
      Go to Electronic Ignition (EI) System Diagnosis
      Go to Step 19

      10
      Remove the spark plug from the cylinders that indicated a misfire. Refer to Spark Plug Replacement .
      Inspect the spark plug. Refer to Spark Plug Inspection .
      Does the spark plug appear to be OK?
      --
      Go to Step 11
      Go to Step 12

      11
      Exchange the suspected spark plug with another cylinder that is operating correctly. Refer to Spark Plug Replacement .
      Operate the vehicle under the same conditions that the misfire occurred.
      Did the misfire move with the spark plug?
      --
      Go to Step 18
      Go to Step 15

      12
      Is the spark plug oil or coolant fouled?
      --
      Go to Symptoms - Engine Mechanical in Engine Mechanical - 1.6L (L91)
      Go to Step 13

      13
      Is the spark plug gas fouled?
      --
      Go to Step 16
      Go to Step 14

      14
      Did the spark plug show any signs of being cracked, worn, or improperly gapped?
      --
      Go to Step 17
      Go to Step 15

      15
      Perform the fuel injector coil test. Refer to Fuel Injector Solenoid Coil Test .
      Did you find and correct the condition?
      --
      Go to Step 20
      Go to Symptoms - Engine Mechanical in Engine Mechanical - 1.6L (L91)

      16
      Perform the fuel system diagnosis. Refer to Fuel System Diagnosis .
      Did you find and correct the condition?
      --
      Go to Step 20
      Go to Symptoms - Engine Mechanical in Engine Mechanical - 1.6L (L91)

      17
      Replace or gap the spark plug. Refer to Spark Plug Replacement .
      Did you complete the action?
      --
      Go to Step 20
      --

      18
      Replace the spark plug. Refer to Spark Plug Replacement .
      Did you complete the replacement?
      --
      Go to Step 20
      --

      19
      Replace the spark plug wires. Refer to Spark Plug Wire Replacement .
      Did you complete the replacement?
      --
      Go to Step 20
      --

      20
      Was the customer concern the malfunction indicator lamp (MIL) flashing?
      --
      Go to Step 21
      Go to Step 22

      21
      Operate the vehicle within the Conditions for Running the DTC P0420 as specified in the supporting text. Refer to DTC P0420 .
      Did the DTC run and pass?
      Go to Step 22
      Go to DTC P0420

      22
      Clear the DTCs with a scan tool.
      Turn OFF the ignition for 30 seconds.
      Start the engine.
      Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
      Did the DTC fail this ignition?
      --
      Go to Step 2
      Go to Step 23

      23
      Observe the Capture Info with a scan tool.
      Are there any DTCs that have not been diagnosed?
      --
      Go to Diagnostic Trouble Code (DTC) List
      System OK

    9. #8
      Aveo Whisperer 06T200's Avatar
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      Steve, do you know when the last time the car had a crank (ckp) relearn? Or if one is needed as this is one way to get p0300 to fire. Also check vacuum lines/leaks if any, maybe even the injector coils, (should be 14 ohms iirc). Just run through the tis steps and see if anything rings a bell or may be the problem. Will need a tech2 to do the CKP relearn though.
      HTH

    10. #9
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      SES and P0300

      #PIP4284A: SES Light And P0300 DTC After Crankshaft Or Engine Replacement - keywords can cylinders feel L91 no not P0301 P0302 P0303 P0304 repair - (May 5, 2008 )














      This PI was superseded to advise that it may be necessary to hold the battery cables together for as long as 15 minutes. Please discard PIP4284.



      The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

      Condition/Concern:



      A SES light may be experienced shortly after crankshaft or engine replacement due to DTCs P0300-P0304 and false engine misfires that count on paired cylinders, such as cylinders 1 and 4, or 2 and 3.

      Recommendation/Instructions:



      If this concern is experienced, perform the following suggestions and re-evaluate the concern (even if a CKP variation learn was performed during the previous repairs):


      1. Disconnect both battery cables.
      2. Hold both battery cables together for up to 15 minutes. Typically, it should only be necessary to hold the cables together for about 1 minute but in some rare instances, it may be necessary to hold the cables together for as long as 15 minutes.
      3. Reconnect both battery cables.
      4. Perform a CKP variation learn with the Tech 2.



      Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

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    12. #10
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      Huh.... Very Useful.

      Diagnostics

      #1 - So eliminate anything causing excess vibration.

      A bolt appears to have sheared off the engine mount where the mount connects to the cradle. - That's interesting.
      So fixing that could be a priority.

      Engine is under load - it's bouncing around, and that could be screaming misfire...
      If this was a misfire for real, I should feel it correct? The steering wheel vibrates, the car makes sounds, sputters and all that right?

      This car does not.

      It could be a vibration issue.
      Examine the belt connecting to the alternator and all that stuff. - that looks possible. Probably due anyways, and probably cheap.





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