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Crazy Horse
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718 Posts
Discussion Starter · #1 ·
2 weeks ago I got a P0300 fault, multiple misfire, and the R was chugging along when accelerating. I had recently installed an LS7 clutch, repaired a rear main seal leak and replaced the crank shaft position sensor as an opportunity while doing the work. As a precaution. I checked the spark plug wires for looseness and after doing that the fault didn’t come back. The truck ran well until today. The fault didn’t show up but it still ran poorly. More like a cough. I am going to take it to a shop and have it put on an analyzer tomorrow and hopefully I can get it repaired. If not, then I’ll either be late or not attend. Any input is appreciated.
 

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Crazy Horse
Joined
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718 Posts
Discussion Starter · #4 ·
Don't you have another vehicle?
Yes but not an SSR. I have to try and get it fixed and I really think it’s a minor problem. I am going to invest in a Tech 2 after this. If I can get it to Cincinnati I’m sure I can get all the help I need. But rather not take the chance.
 

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Premium Member
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7,725 Posts
Mine acted up like that a couple years ago and replaced wires and plugs. Straighten it out. Could go the whole route and replace coil packs also.
 

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Premium Member
Joined
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3,620 Posts
Probably needs a tune up , you can't tell if plug wires a good by looking at them !!
 

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Crazy Horse
Joined
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718 Posts
Discussion Starter · #10 ·
Mine acted up like that a couple years ago and replaced wires and plugs. Straighten it out. Could go the whole route and replace coil packs also.
Wires and plugs replaced 2 years ago. I had the battery completely disconnected prior to the clutch job and I'm praying it is the ground. I'll know in a little while. The problem is intermittent so it could very well be!
 

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Crazy Horse
Joined
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718 Posts
Discussion Starter · #11 ·
Wires and plugs replaced 2 years ago. I had the battery completely disconnected prior to the clutch job and I'm praying it is the ground. I'll know in a little while. The problem is intermittent so it could very well be!
 

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Premium Member
04 SSR
Joined
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3,690 Posts
@Light Show
While it may be an ignition problem.
It needs to have a CKP variation relearn procedure performed. The service manual recommends that this is done after replacing crank sensor (also required with other part replacements)
This is accomplished using a scan tool to put it into the proper mode and operating engine as directed (its scary, as it has you Rev against Rev limiter)

I copied this from the service manual (note the line I enlarged near the bottom)

CKP SYSTEM VARIATION LEARN PROCEDURE

1. Install a scan tool.
2. Monitor the engine control module (ECM) for DTCs with a scan tool. If other DTCs are set, except DTC P0315, refer to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information for the applicable DTC that set.
3. Select the crankshaft position (CKP) variation learn procedure with a scan tool.
4. The scan tool instructs you to perform the following:
1. Accelerate to wide open throttle (WOT).
2. Release throttle when fuel cut-off occurs.
3. Observe fuel cut-off for applicable engine.
4. Engine should not accelerate beyond calibrated RPM value.
5. Release throttle immediately if value is exceeded.
6. Block drive wheels.
7. Set parking brake.
8. DO NOT apply brake pedal.
9. Cycle ignition from OFF to ON.
10. Apply and hold brake pedal.
11. Start and idle engine.
12. Turn A/C OFF.
13. Vehicle must remain in Park or Neutral.
14. The scan tool monitors certain component signals to determine if all the conditions are met to continue with the procedure. The scan tool only displays the condition that inhibits the procedure. The scan tool monitors the following components:
- CKP sensors activity-If there is a CKP sensor condition, refer to the applicable DTC that set.
- Camshaft position (CMP) sensor activity-If there is a CMP sensor condition, refer to the applicable DTC that set.
- Engine coolant temperature (ECT)-If the ECT is not warm enough, idle the engine until the engine coolant temperature reaches the correct temperature.
5. Enable the CKP system variation learn procedure with a scan tool.
6. Accelerate to WOT.

IMPORTANT: While the learn procedure is in progress, release the throttle immediately when the engine starts to decelerate. The engine control is returned to the operator and the engine responds to throttle position after the learn procedure is complete.

7. Release when the fuel cut-off occurs.
8. Test in progress
9. The scan tool displays Learn Status: Learned this ignition. If the scan tool indicates that DTC P0315 ran and passed, the CKP variation learn procedure is complete. If the scan tool indicates DTC P0315 failed or did not run, refer to DTC P0315. If any other DTCs set, refer to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information for the applicable DTC that set.
10. Turn OFF the ignition for 30 seconds after the learn procedure is completed successfully.
11. The CKP system variation learn procedure is also required when the following service procedures have been performed, regardless of whether DTC P0315 is set:
- A CKP sensor replacement
- An engine replacement
- A ECM replacement
- A harmonic balancer replacement
- A crankshaft replacement

- Any engine repairs which disturb the CKP sensor relationship

Before doing this have the shop check misfire history while problem is occurring.

Perform the relearn procedure and then recheck for misfire history. if no more misfires - this is was likely the issue.

I am in class most of the afternoon and until 10pm tomorrow night but I will check for updates and provide assistance if needed.

OH, This will not change any custom tunes. I personally can't tell you if a custom will prevent you from doing this relearn but I would not think so. Its just if your tune has increased REV limiter (fuel cut off RPM) I am not sure. I don't mess with that part of tune.

EDIT - NOTE after step 4 numbers start over - these next 14 steps should be indented and are letting you know in advance what the scan tool will be asking yo to do. The actual steps resume further done at step 5.
 

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Tech Support/Research
Joined
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1,866 Posts
The diagnostic readout from a good scan tool will show both current and historical misfires under DTC P0300 (random misfires). From my experience, the most common culprits are spark plugs and wires, which mysteriously fail without notice. If there are no other codes and no other issues with the coils or injectors (both can be easily tested), and, as @Autoprof notes, your truck's crank positoin sensor relearn has been done, replacing all spark plug wires and plugs at the same time would be my recommendation. Misfires will usually be accompanied by a flashing check engine light. Don't drive very far while this light is flashing- the catalytic converters can be ruined by running a rich fuel mixture through them and overheating them.
 

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Crazy Horse
Joined
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718 Posts
Discussion Starter · #16 ·
@Light Show
While it may be an ignition problem.
It needs to have a CKP variation relearn procedure performed. The service manual recommends that this is done after replacing crank sensor (also required with other part replacements)
This is accomplished using a scan tool to put it into the proper mode and operating engine as directed (its scary, as it has you Rev against Rev limiter)

I copied this from the service manual (note the line I enlarged near the bottom)

CKP SYSTEM VARIATION LEARN PROCEDURE

1. Install a scan tool.
2. Monitor the engine control module (ECM) for DTCs with a scan tool. If other DTCs are set, except DTC P0315, refer to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information for the applicable DTC that set.
3. Select the crankshaft position (CKP) variation learn procedure with a scan tool.
4. The scan tool instructs you to perform the following:
1. Accelerate to wide open throttle (WOT).
2. Release throttle when fuel cut-off occurs.
3. Observe fuel cut-off for applicable engine.
4. Engine should not accelerate beyond calibrated RPM value.
5. Release throttle immediately if value is exceeded.
6. Block drive wheels.
7. Set parking brake.
8. DO NOT apply brake pedal.
9. Cycle ignition from OFF to ON.
10. Apply and hold brake pedal.
11. Start and idle engine.
12. Turn A/C OFF.
13. Vehicle must remain in Park or Neutral.
14. The scan tool monitors certain component signals to determine if all the conditions are met to continue with the procedure. The scan tool only displays the condition that inhibits the procedure. The scan tool monitors the following components:
- CKP sensors activity-If there is a CKP sensor condition, refer to the applicable DTC that set.
- Camshaft position (CMP) sensor activity-If there is a CMP sensor condition, refer to the applicable DTC that set.
- Engine coolant temperature (ECT)-If the ECT is not warm enough, idle the engine until the engine coolant temperature reaches the correct temperature.
5. Enable the CKP system variation learn procedure with a scan tool.
6. Accelerate to WOT.

IMPORTANT: While the learn procedure is in progress, release the throttle immediately when the engine starts to decelerate. The engine control is returned to the operator and the engine responds to throttle position after the learn procedure is complete.

7. Release when the fuel cut-off occurs.
8. Test in progress
9. The scan tool displays Learn Status: Learned this ignition. If the scan tool indicates that DTC P0315 ran and passed, the CKP variation learn procedure is complete. If the scan tool indicates DTC P0315 failed or did not run, refer to DTC P0315. If any other DTCs set, refer to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information for the applicable DTC that set.
10. Turn OFF the ignition for 30 seconds after the learn procedure is completed successfully.
11. The CKP system variation learn procedure is also required when the following service procedures have been performed, regardless of whether DTC P0315 is set:
- A CKP sensor replacement
- An engine replacement
- A ECM replacement
- A harmonic balancer replacement
- A crankshaft replacement

- Any engine repairs which disturb the CKP sensor relationship

Before doing this have the shop check misfire history while problem is occurring.

Perform the relearn procedure and then recheck for misfire history. if no more misfires - this is was likely the issue.

I am in class most of the afternoon and until 10pm tomorrow night but I will check for updates and provide assistance if needed.

OH, This will not change any custom tunes. I personally can't tell you if a custom will prevent you from doing this relearn but I would not think so. Its just if your tune has increased REV limiter (fuel cut off RPM) I am not sure. I don't mess with that part of tune.

EDIT - NOTE after step 4 numbers start over - these next 14 steps should be indented and are letting you know in advance what the scan tool will be asking yo to do. The actual steps resume further done at step 5.
Autoprof: I just checked the ground on the battery and ran it for ten or so miles even over a bridge with a 30 deg incline in 6th gear at 55 mph. Did not throw the code and no chugging. I think it could have ben the ground but not sure at this point. What I would like to do is attempt the trip to Cincinnati and do the procedure there. I really don't trust the mechanics to work on it and do anything that they may may not be familiar with. When it first threw the code, it wasn't flashing. But the code was in the temporary file. Once I cleared the code it hasn't come back. I initially thought i had gotten some bad gasoline I refilled the tank but still no code. So, with that said, I did change the Crank sensor and in my view, my timing is slightly off. Not enough for multiple misfires. In Cincinnati, I will get with Joe Delano and see what he might can do since he did a retune in Branson. I think you are 100% right about doing the CKP Learn procedure! Thanks for all you do!
 

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Chevrolet Nut
Joined
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1,440 Posts
As a suggestion if you have a local community college auto program they may be able to look at it for you and give you some repair help. After 30 years teaching at a community college we did it all the time to help the public out, as long as it fit the classes we were teaching at the time.
 
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