Phantom Timing Retard. HELP!

[LNorton]

Still having an issue with timing. I'm beyond stumped. Doesn't do it every run, but it pulls 6-7* of timing in high gear. Been doing it for a while, and I am out of solutions. No KR.

Scan and Tune attached.

[LNorton]

I just ran across some files from a former V6 guy that I had stashed away. Never noticed before but it did the same thing in his car. Pulls 8* at 6,500 in one run and 8* at 5,750 in another run.

I'm starting to believe that no one has a clue on this one.

[TurboGP33]

IDK but that is perplexing.

I would guess possibly the PCM sees the RPM not climbing as fast, appearing near steady and commands idle spark?

Or maybe going into High RPM (trim 4 for most) past trim 3 WOT.

There may be a table unaccessible in HPT that needs tuned out. Have you tried tiny tuners (if you can get the BIN of your PCM working with)?



EDIT: Just checked your PCM file you provided. Your spark limit is set WAY to low. Like 2700 RPM at 26 spark. Not supposed to be that way. Set that to the max red line (mine is 6500 rpm) and 0 degrees for redline safety.

It appears, though not sure, that you might be in a limp home mode of spark commanded when the PCM realizes it is past the spark limiter for quite some time.

[LNorton]

I've been through the Tiny Tuner bit. Every spark advance or retard table has been disabled. I know that the spark limit is set low. I have done that recently as to attempt to mask the problem but it didn't work. I can set that back up to 7,200 and it will do the same thing.

Only thing I am wondering about is that it is setup as a manual trans tune because the computer has no control of the transmisison, but I do not have any speed or wheel sensors hooked up. Would that possibly cause an issue?

[Overkill]

For good measure, ensure you fully disable the abuse modes in the TM tab by making the appropriate engine and vehicle speed inputs.

[LNorton]

Just made a few changes there for good measure. Really don't think that is it though. Should be good there either way as I will have a speed sensor in for the next outing.

[TurboGP33]

I've been through the Tiny Tuner bit. Every spark advance or retard table has been disabled. I know that the spark limit is set low. I have done that recently as to attempt to mask the problem but it didn't work. I can set that back up to 7,200 and it will do the same thing.

Only thing I am wondering about is that it is setup as a manual trans tune because the computer has no control of the transmisison, but I do not have any speed or wheel sensors hooked up. Would that possibly cause an issue?

It is definitely worth a try adding those sensors. Suppose this is the spark changes from the PCM thinking it is locking up the TCC.

[LNorton]

It is definitely worth a try adding those sensors. Suppose this is the spark changes from the PCM thinking it is locking up the TCC.

Wired up a VSS last night. I figure it can't hurt anything.

[TurboGP33]

Good idea, seems the PCM might think it is commanding idle conditions when the RPM levels out, even at higher rpm.

Similar function occurs with the barometric value. The barometric value is obtained from the MAP sensor key on/not running (naturally this is atmospheric pressure). If the pcm sees a rise in the map beyond barometric it will disregard as a very efficient moment while driving. But with a turbo, the map max's out at 105 kPa and the steady signal tells the PCM to make this the new barometric pressure.

It's called Barometric Relearn Function and is a royal PITA tuning a MAF/1bar MAP set up with boost. It is useful for those who drive non-stop from a mountain elevation to the shore. The change in baro is needed to recalc proper fueling. But in this instance, modification triggers an undesired result. It is possible your mods might have triggered this behavior through one action or another.

Are your TCC tables maxed out? Seeming the effect is close in RPM but not RPM specific, it may indicate the value is a transmission one where both RPM and MPH are used to determine TCC, gear shift, etc. Assuming the proper MPH trigger is the same to the suspected setting.


Look in Tiny Tuners for a Spark value adjuster while the TCC is locked (or atleast commanded locked). Maybe you could hook up a dummy light to the VCC control wire to see if the light turns on the same time the spark changes occur. Or log the signal wire some how. You might be able to log TCC activation in status bits.


EDIT: After viewing your PCM file again, I noticed most the transmission values are zero. Try setting them to their maximum instead. Keep the PCM out of trying to shift all gears at once. The confusion might trigger a limp home or some goofy spark change. Let the PCM think the gears and TCC need activated when 9000 RPM is reached (you'll never see it and thus the PCM never engages any special functions for shift/tcc stuff).......worth a shot!

[LNorton]

PCM does not have control of the transmission.

[LNorton]

Look in Tiny Tuners for a Spark value adjuster while the TCC is locked (or atleast commanded locked). Maybe you could hook up a dummy light to the VCC control wire to see if the light turns on the same time the spark changes occur. Or log the signal wire some how. You might be able to log TCC activation in status bits.

Went back through Tiny Tuner again. Every single correction table is zeroed out. Can't find it.

[TurboGP33]

PCM does not have control of the transmission.

Yes I get that, BUT the PCm will make spark changes according to what it THINKS it is doing to the trans. It doesn't need control to attempt control and thus make spark changes. When the TCC locks up the spark is altered. If the PCM thinks it is locking up/unlocking the TCC, spark changes will occur. Same with EGR.

Or is your PCM set to manual trans mode?

Basically, if the PCM is separated from the trans electronically and doesn't know it, it will still operate as normal and corresponding spark changes will happen as if the trans was connected electronically.




Also, try maxing out the tables instead of zero. Because zero can be a true condition at rest, idle, etc. The PCM may try to do too many things at once and bottle neck the communications line.

Zero is also considered a turn off for some digital systems. Just for trial, anything that can be maxed instead of zeroed might help.....worth a shot!




Try commanding specific gears in the scanner to see if you can aggravate the spark changes.

[LNorton]

It was in auto trans mode, but every spark correction for any trans function was zeroed out.

I have since added the VSS and changed the bin to reflect a manual trans. I'm thinking this might take care of the problem.

[TurboGP33]

It was in auto trans mode, but every spark correction for any trans function was zeroed out.

I have since added the VSS and changed the bin to reflect a manual trans. I'm thinking this might take care of the problem.

Probably, especially changing to manual trans mode. If the problem persists, it isn't a function of the trans operation. Beyond that, I believe the EGR is the only system that can change spark values outside of normal operation.


As far as tables not being used, sometimes it is best to max them out instead of setting zeroes. Like trans shift points if a manual is used with an auto trans PCM. Or if you want to not use the TCC, maxing the table is the only way to "zero" it out. Otherwise, you may inadvertently command a function at idle/rest. It depends on the table itself so there is obvious discretion upon the user.

Just trying to help. Hope those changes you made does it.


EDIT: Thinking on it, if the problem persists, try max'ing the EGR activation temp to disable any EGR function.