An HP tuner fail....

[rdezs]

Guided a friend of mine that lives 100 miles away on doing his AFM delete about 6 months ago. (He's rebuilt a lot of small block Chevys back in the day)

He bought an HP tuner, turned off the AFM, and did the CASE relearn. About once every 2 weeks, he would get a trouble code for knock sensors. (Running premium fuel, code would pop up when cruising at 60 MPH)

He brought the vehicle down yesterday to have me take a look at it. My Tech 2 showed at idle he had a random misfire about once every 90 cycles. Basically imperceptible.

We did the CASE relearn using his HP tuners. No change on the random misfire while doing a 10 mile drive.

Used my Tech 2 and repeated the case relearn. All misfires disappeared.

He used all genuine GM ACDelco sensors, and an oem L9h camshaft, retaining VVT on his 6.2.

I'm a little perplexed by this, thought HP tuners was pretty much top of the line?

 

[B-train]

That is a bummer. I was hoping for that feature to work if I replace the CPS that seems to be getting flaky with age. I'll make sure I have a second option I guess....

Have you, or him, reached out to HP Tuners about this? More as a FYI for them in case there is some software update that needs to be adjusted?

 

[Scrappycrow]

When is a CASE relearn advised? I turned off AFM in my Tahoe using HP Tuners over a year and 10K miles ago without doing a relearn and haven't had any problems (that I've noticed). I did the same on a buddy's Silverado and no problems there, either.

 

[mikez71]

Same, never did relearn when turning off AFM.
I thought it was only needed when replacing the crank sensor..

Here's some info from Alvin on hptuners forum...

Functional question for Cam Crank Relearn for 2011 Silverado

Hopefully a quick one and I won't get overly flamed. We've got that PITA 2011 Silverado. Now we will need to have the VVT deleted once we get the cam sensor issues worked out. I get it- We'll need the HP tuner equipment to pull it off. Local guy quoted me $500 to do this procedure. I...

forum.hptuners.com

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I've used HPtuners for CASE relearn. It doesn't seem as fool proof or shaken out as a legit scan tool for this. A dealership tool will prompt you to make sure the E brake is set, foot brake is pressed, temp is X.. HPtuners does not. So make sure you do those things because HPTuners will not prompt you to do it and the CASE relearn might not work.

I've heard that a CASE relearn will automatically happen after so many drive cycles. I can't promise that though.

Another note. CASE relearn is really only for detecting misfires. It doesn't effect how the vehicle runs. It isn't absolutely required.
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[rdezs]

It's not needed unless changing the cam or crank sensors, or any of the timing components. Simply turning off AFM, it won't be needed.

His vehicle was actually running just fine, the misfires were so rare and imperceptible.... The only clue was occasionally the knock sensor code popped up.

That's interesting that HP tuners lacks the verification of parking brake, temperature, etc. That in itself is a software flaw in HP tuners.

The reason I say that is because what the Tech 2 instructs you to do has some differences between the 2003 model year and the 2014. Different ECM software obviously.

Interesting, I suppose this puts us back to the standard of only using genuine GM or AC Delco parts.... It appears that also applies to bidirectional scanners for some things.

 

[rdezs]

An additional thought.... While his drivability wasn't affected, just an occasional knock sensor code.... Makes me wonder if sometimes when a cylinder doesn't fire, then fires on the next cycle, that might result in a ping picked up by the knock sensor?

He said he'll be calling HP tuners on Monday. And it still does have a lot of features for tuning that you don't get with the Tech 2. (Absolutely required if going with an aftermarket camshaft or other modifications to OEM)

 

[Marky Dissod]

I'm a little perplexed by this, thought HPTuners was pretty much top of the line?

That's interesting that HPTuners lacks the verification of parking brake, temperature, etc. That in itself is a software flaw in HP tuners.

All HPTuners provides is basically decoder rings.

HPTuners & EFI Live are pretty much the only games in town for making sense of what the ecm & tcm have available to be tuned.
The engine & the parking brake don't have anything to do with each other on the GMT900, but they do share info with other control modules.

Also, if you are using HPTuners AFTER version 2.2.4 (I think), HPTuners kinda hamstrung it ...
OK

1st: disable the CASE relearn requirement and relax the misfire thresholds (if it lets you do so).
2nd:

About once every 2 weeks, he would get a trouble code for knock sensors. Running premium fuel, code would pop up when cruising at 60 MpH.

At what RpM, at what MAP, at what TPS%, in what gear?
Is the random misfire 'located' in the same 'place', or really close to it?
The more precisely this knock event is located, the smaller the adjustment needed to stop it.
My guess is lower 1.5-2.0 degrees from a single spark timing cell at low load in the high octane table.
If after the adjustment, the knock retard is IDENTICAL to the previous knock events,
it's likely a false knock, in which case you need to either physically tighten something near the knock sensors, or you need new knock sensors.

 

[rdezs]

The random misfire was quite minor. Picture a misfire about every 65 seconds, on a different cylinder every time. And strangely this was consistent throughout a 10-mile test drive up to 65 mph. (I would have expected it to increase with RPM)

Knock sensors tested out perfect.

After completing the CASE relearn with the Tech 2, absolutely zero misfires, repeating the 10 mile test drive.

I feel quite strongly it's better to address the problem correctly then try to mask it by altering the timing or other parameters. (In an oem configured engine)

I was actually leaning towards a possible issue with the wrong spec of spark plugs or wires, until I saw the Tech 2 completely resolve the issue.

There were no pending codes for misfires, so I can only surmise that the misfires were below the threshold required.

This does make me ponder the many posts over the years where people are hopelessly throwing parts at a random misfire with no luck..... Worth considering next time we get a post like that.

 

[Joseph Garcia]

The random misfire was quite minor. Picture a misfire about every 65 seconds, on a different cylinder every time. And strangely this was consistent throughout a 10-mile test drive up to 65 mph. (I would have expected it to increase with RPM)

Knock sensors tested out perfect.

After completing the CASE relearn with the Tech 2, absolutely zero misfires, repeating the 10 mile test drive.

I feel quite strongly it's better to address the problem correctly then try to mask it by altering the timing or other parameters. (In an oem configured engine)

I was actually leaning towards a possible issue with the wrong spec of spark plugs or wires, until I saw the Tech 2 completely resolve the issue.

There were no pending codes for misfires, so I can only surmise that the misfires were below the threshold required.

This does make me ponder the many posts over the years where people are hopelessly throwing parts at a random misfire with no luck..... Worth considering next time we get a post like that.

I'll say it again, the Tech 2 is a wonderful bi-directional scanner and diagnostic tool and procedure activating tool, for those trucks manufactured in 2013 and before.
I've saved thousands of dollars in diagnostic and repair costs over the time of my ownership, and it easily payed for itself (~$350) within 1 year.

 

[rdezs]

Works great on the 2014 models as well.... And I don't ever plan on having anything newer than that.