LSX 376 B15 Misfire, does not reproduce during Crank Sensor Re-Learn

[RonVC]

LSX 376 B15 ~30k miles with TVS-1900 Maggie and BTS Stage 2 Forced Induction Cam.....

Been chasing misfire at operating temperature...

Does not reproduce at initial/cold-start, begins as reached operating temps...

No Mis-Fire counts OR DTC's being generated.

Here is the question.

The Mis-Fire does not reproduce during the Crank Sensor Re-Learn process.
IE: When slowly rev the rpm's to 4k and the engine reaches cutout at 4K
As soon as ignition on,off and restart, to complete the Crank Sensor Re-Learn process then Mis-Fire returns.

Any idea's why the misfire would not reproduce during Crank Sensor Re-Learn process?

Any chance there is something wonky with the Engine timing/Advance circuitry,
Which might also explain why Mis-Fire does not repro on cold-start, until reaches operating temps. ~180

Thanks in advance!

[blindsquirrel]

I've never done the relearn by slowly applying throttle, just put it to the mat until it cuts off and decelerates on its own.

Does it have real misfires (if so, getting the relearn to work will not stop it from misfiring) or is it detecting misfires that aren't really there?

[RonVC]

RE: ..never done the relearn by slowly applying throttle, just put it to the mat until it cuts off and decelerates on its own
Ok, from 1k to 4k "slowly" means in about 3-5 seconds, not a WOT type of rev.... Per the instructions....

RE: Does it have real misfires (if so, getting the relearn to work will not stop it from misfiring) or is it detecting misfires that aren't really there?
Real MisFire, quite bad, like down 2 cylinders.

This from description, with bit more details -->
1) Does not reproduce at initial/cold-start, Mis-Fire begins/increases as engine reaches operating temps...

2) No Mis-Fire counts OR DTC's being generated. Have seen 1 occurrence of P0355 during Crank Sensor Re-Learn

3) The Mis-Fire does not reproduce during the Crank Sensor Re-Learn process. IE: When increasing rpm to 4k in about 3-5 seconds.

Thanks!

[blindsquirrel]

The GM service manual says different.

5. Enable the CKP System Variation Learn Procedure with a scan tool.

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.

6. Accelerate to WOT.
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 for the applicable DTC that set.
10. Turn OFF the ignition for 30 seconds after the learn procedure is completed successfully.

[blindsquirrel]

And again, performing the relearn will not fix a misfire, it will only prevent false misfire detection when there aren't really any misfires. You're going down a rabbit hole. The relearn is not your problem.

[RonVC]

performing the relearn will not fix a misfire

Thanks for the comment, the description in no way should be interpreted as suggesting executing the Crank Sensor ReLearn will resolve a Misfire condition!

What the description tries to ask/convey is, does anybody have ideas why during the Crank Sensor ReLearn process the Mis-Fire does not reproduce.
Which, in case unclear, if execute the same 1k to 4k rpm increase the Mis-Fire is reproducible, just does NOT reproduce during Crank Sensor ReLearn process.

Suspecting something to do with Ignition Timing, that is defeated during Crank Sensor ReLearn process.

Also, in the description try to describe that the Mis-Fire does not reproduce until engine is at operating temperature.
As the engine warms-up, the Mis-Fire gets increasingly more severe.
Again, suspecting has to do with some timing management process that not familiar with.

Hopefully that helps to clarify the question.

Not asking how, why to perform Crank Sensor ReLearn process, asking if anybody has ideas as to why the Mis-Fire would not reproduce during the Crank Sensor ReLearn process?

[blindsquirrel]

Right. And the interesting thing you found is the rabbit hole. Forget all about the CKP relearn thing and diagnose the misfire.

[RonVC]

Right. And the interesting thing you found is the rabbit hole. Forget all about the CKP relearn thing and diagnose the misfire.

Um, Ok, great advice, have a nice day. -> "This message is hidden because blindsquirrel is on your ignore list. "

[GHuggins]

Blind's not wrong here. Misfires won't register during the relearn process because the crank position sensor is now null and void until it is relearned. You can make the ecm ignore misfires in the same manner by starting the crank relearn and not completing it. It will continue ignoring misfires until it relearns the crank position. The crank position is how it knows what cylinder is firing and which is number 1 to be able to report the misfires.

If I'm understanding you correctly the engine won't misfire at all during a crank relearn. Honestly sounds like you have a couple of week cylinders and misfires aren't completely killed in the calibration and it's "possibly" registering some then killing those cylinders completely as it's designed to do with it's save cats routines. Simple test for that is to kill misfire test then re-evaluate things.

It's also possible since it just started that your ecm is going and not firing a couple of injectors or coils. Also possible that you have partially clogged injectors and as the OL fueling is removed it's getting too lean on a couple. Only seen this once, but the crank reluctor is bent or shifted and not firing two cylinders right after one another in the firing order.

Anything's possible. Best to post the log and tune

[RonVC]

RE: continue ignoring misfires until it relearns the crank position
Are you able to elaborate, when I mention Mis-Fires, these are not ECM reported Mis-Fires, these are obvious engine not running smooth Mis-Fires.
There are no DTC's registered during, after, before the Crank Sensor Re-Learn.

So, when say the Mis-Fire does not repro during Crank Sensor Re-Learn, referring to physically observable Mis-fires, not ECM reported or HPTuners observable Mis-Fires.

There are zero Mis-Fire counters being registered/reported.

RE: Best to post the log and tune
Tune attached, not fluent enough with VCM Scanner to know what log's to capture, if someone could help with a VCM Configuration to capture the logs, will attach.

[RonVC]

RE: Also possible that you have partially clogged injectors and as the OL fueling is removed it's getting too lean on a couple
--> Injectors flowing good, Compression ~145 all cylinders, New coils, Wires, Plugs.

[edcmat-l1]

And again, performing the relearn will not fix a misfire, it will only prevent false misfire detection when there aren't really any misfires. You're going down a rabbit hole. The relearn is not your problem.

That is correct. Only reason for the crank relearn is for misfire ID. If the crank relearn does not complete, misfire detection is disabled.

[edcmat-l1]

Forget all about the CKP relearn thing and diagnose the misfire.

This ^^^^

Need to follow a standard misfire diagnostic approach. Check header temps. Check secondary ignition components. Pull plugs, check compression, leakdown, etc.

[RonVC]

This ^^^^

Need to follow a standard misfire diagnostic approach. Check header temps. Check secondary ignition components. Pull plugs, check compression, leakdown, etc.

Um, if any of those scenarios were a problem, then Mis-Fire would reproduce during Crank Sensor Re-Learn process.

With that said, only 1 of those not checked is the "leakdown", which as mentioned would not go-away during Crank Sensor Re-Learn process.

Gee Whiz.

[edcmat-l1]

Um, if any of those scenarios were a problem, then Mis-Fire would reproduce during Crank Sensor Re-Learn process.

With that said, only 1 of those not checked is the "leakdown", which as mentioned would not go-away during Crank Sensor Re-Learn process.

Gee Whiz.

Yep, you're right and I am wrong. Really sounds like ya got a handle on it! Carry on......

[gtstorey]

Um, if any of those scenarios were a problem, then Mis-Fire would reproduce during Crank Sensor Re-Learn process.

With that said, only 1 of those not checked is the "leakdown", which as mentioned would not go-away during Crank Sensor Re-Learn process.

Gee Whiz.

You do realize that you have 3 of the most experienced people on here telling you the same thing? Maybe all of them are wrong, but you are probably on your own with a very unusual problem. At some point the only overlap of the problems is the ECM doing something very strange.

[Alvin]

LSX 376 B15 ~30k miles with TVS-1900 Maggie and BTS Stage 2 Forced Induction Cam.....

Been chasing misfire at operating temperature...

Does not reproduce at initial/cold-start, begins as reached operating temps...

No Mis-Fire counts OR DTC's being generated.

Here is the question.

The Mis-Fire does not reproduce during the Crank Sensor Re-Learn process.
IE: When slowly rev the rpm's to 4k and the engine reaches cutout at 4K
As soon as ignition on,off and restart, to complete the Crank Sensor Re-Learn process then Mis-Fire returns.

Any idea's why the misfire would not reproduce during Crank Sensor Re-Learn process?

Any chance there is something wonky with the Engine timing/Advance circuitry,
Which might also explain why Mis-Fire does not repro on cold-start, until reaches operating temps. ~180

Thanks in advance!

How do you know it is misfiring? Is it something you hear or feel?

The stock misfire diagnostics are going to be useless with a cam.

[edcmat-l1]

Um, if any of those scenarios were a problem, then Mis-Fire would reproduce during Crank Sensor Re-Learn process.

With that said, only 1 of those not checked is the "leakdown", which as mentioned would not go-away during Crank Sensor Re-Learn process.

Gee Whiz.

Stop saying that. Forget about the crank relearn process. Turn the code off.

Have you figured out what cylinders are missing when it starts missing? If you're smart enough to get this far into it ya gotta be smart enough to figure out which cylinders are missing. Figure out exactly what cylinders and let's go from there.

[edcmat-l1]

RE: Does it have real misfires (if so, getting the relearn to work will not stop it from misfiring) or is it detecting misfires that aren't really there?
Real MisFire, quite bad, like down 2 cylinders.

That should be easy to nail down if it's that bad. Header temp should tell you at that point. If not that, cylinder balance definitely would.

[GHuggins]

OK, your misfires are disabled in the tune. Put stock values back into the engine diagnostic misfire section then log current and history misfires for each cylinder. The one with a dead miss will constantly count up. Those are the ones to focus on. You can post the log after enabling misfires... Do a slight rev from idle too - somewhere up around holding at 1200 or 1500 rpms should work fine. If you don't have your stock tune to get the misfire settings from then go to the repository under after clicking on your name on hp tuners website. If you haven't done so you may need to set up an account to do so.

All of us in here right now I think were or are go to drivability techs that spent years diagnosing things like this, so there is that