Misfiring issue, no codes, need a guru's help
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Registered User
Joined: Sep 2010
Posts: 3
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Misfiring issue, no codes, need a guru's help Hey Guys,
Been a gearhead for sometime, even built LSx harnesses and programmed pcms on the side, with very little issues. Nothing like this: put together a nice LS6 for myself. Fire it off and it runs like crap, throws the infamous code 1336. Found the CKP sensor is being slightly nicked by the reluctor ( this is a new reluctor and sensor). Installed the old CKP sensor that wasnt nicked, and the same visual indication. Found the shim that GM makes to address the issue, under part number 12565102, they are .020 thickness, so I installed two, turned the crank by hand, with the sensor tester plus hooked up and have 24 distinct pulses. Fire up engine, same code 1336 and code 0200 ( Injector circuit open). Then I reprogrammed another pcm, and activated the code P1345 ( Crank/cam pos. correaltion) just to see if it would be a timing issue, installed, fired up and no codes. Good sign, however it still will not fire on all cylinders. Here is my observations:
1. Battery voltage at 14.3V when running
2. All grounds have been verified
3. All coils are getting a pulse when running
4. Verified injector circuits with noid light, all are firing, with engine not running, resistance of all injectors are well within specs.
5. With engine running, only cylinders 1-6, 7-4 are firing. If you look at the firing order, these are companion cylinders, with 5-8, 2-3 not getting any injector pulses.
I suspect the cam timing may be off, even though it is not throwing the P1345 code?
When I put this engine together, I used the Goodson reluctor tool to properly index the wheel in relation to the crank. I took pictures of this and verified the proper orientation, which is the same on the instructions, and in a rebuild book I have as well.
Is there a spec to show how much air gap is needed between the CKP sensor and reluctor?
I thought I have seen it all, but this is really kicking my butt and I would appreciate in advance any suggestions and ideas.
I would really like to get this on the street.
Been a gearhead for sometime, even built LSx harnesses and programmed pcms on the side, with very little issues. Nothing like this: put together a nice LS6 for myself. Fire it off and it runs like crap, throws the infamous code 1336. Found the CKP sensor is being slightly nicked by the reluctor ( this is a new reluctor and sensor). Installed the old CKP sensor that wasnt nicked, and the same visual indication. Found the shim that GM makes to address the issue, under part number 12565102, they are .020 thickness, so I installed two, turned the crank by hand, with the sensor tester plus hooked up and have 24 distinct pulses. Fire up engine, same code 1336 and code 0200 ( Injector circuit open). Then I reprogrammed another pcm, and activated the code P1345 ( Crank/cam pos. correaltion) just to see if it would be a timing issue, installed, fired up and no codes. Good sign, however it still will not fire on all cylinders. Here is my observations:
1. Battery voltage at 14.3V when running
2. All grounds have been verified
3. All coils are getting a pulse when running
4. Verified injector circuits with noid light, all are firing, with engine not running, resistance of all injectors are well within specs.
5. With engine running, only cylinders 1-6, 7-4 are firing. If you look at the firing order, these are companion cylinders, with 5-8, 2-3 not getting any injector pulses.
I suspect the cam timing may be off, even though it is not throwing the P1345 code?
When I put this engine together, I used the Goodson reluctor tool to properly index the wheel in relation to the crank. I took pictures of this and verified the proper orientation, which is the same on the instructions, and in a rebuild book I have as well.
Is there a spec to show how much air gap is needed between the CKP sensor and reluctor?
I thought I have seen it all, but this is really kicking my butt and I would appreciate in advance any suggestions and ideas.
I would really like to get this on the street.
Thread Starter
Registered User
Joined: Sep 2010
Posts: 3
Likes: 0
This is what I have done so far:
1) Timing gears at correct position
2) Reluctor is at correct phasing, < .015" run out, air gap around .030"
3) Injectors check out at around 12.5 ohms +/- .5 ohms
4) Noid light pulses on all injector connectors
5) No shorts to ground, or voltage. Solid 13.8 V at injectors with engine running. 14.5 output at the alternator.
6) All ignition coils are firing, even though the engine is only firing on the companion cylinders ( 1,6 and 4,7)
During further observation this what I found.
With the engine first started (stone cold) all the injectors are firing. I connected a noid light to the suspected injector pair (2,3 ) that does not fire with the engine hot. What I found is that all injectors fire on initial start up BUT when you rev the motor above idle the noid light will quit blinking and you can hear and feel the roughness in the engine.
Another thing I notice, is about a minute or so with the engine running, the injector pairs (2,3) and (5,8) do drop off where the engine is only now firing 4 injectors.
My question is, even with no codes set, do I still need to do a crank learn procedure? They way it acts when the engine is first started and revved up, does the pcm loose it reference position, and with the engine going to close loop and it cannot readily indentify the timing coorelation and go to a "safe" mode".
Any answer to this would be much appreciated and thanks in advance for your help.
1) Timing gears at correct position
2) Reluctor is at correct phasing, < .015" run out, air gap around .030"
3) Injectors check out at around 12.5 ohms +/- .5 ohms
4) Noid light pulses on all injector connectors
5) No shorts to ground, or voltage. Solid 13.8 V at injectors with engine running. 14.5 output at the alternator.
6) All ignition coils are firing, even though the engine is only firing on the companion cylinders ( 1,6 and 4,7)
During further observation this what I found.
With the engine first started (stone cold) all the injectors are firing. I connected a noid light to the suspected injector pair (2,3 ) that does not fire with the engine hot. What I found is that all injectors fire on initial start up BUT when you rev the motor above idle the noid light will quit blinking and you can hear and feel the roughness in the engine.
Another thing I notice, is about a minute or so with the engine running, the injector pairs (2,3) and (5,8) do drop off where the engine is only now firing 4 injectors.
My question is, even with no codes set, do I still need to do a crank learn procedure? They way it acts when the engine is first started and revved up, does the pcm loose it reference position, and with the engine going to close loop and it cannot readily indentify the timing coorelation and go to a "safe" mode".
Any answer to this would be much appreciated and thanks in advance for your help.
