DóòD

I got my HPtuner goodies earlier this week...
(Since deciding to order, I've been going over this forum bigtime trying to get some background and information on this problem..)

I put together some scans logs, scan configs, and tunes that I tried. Not much worked to solve the issue. No DTC codes triggered during the logging.

Raising the 3-4 shift to 40mph seemed to mitigate it, but not solve it. :shrug:

Here is a link to the efforts.
http://www.doodnet.com/hpt/goofytrans.zip

Included are a few tunes, a scan log, and the config I used for the scan.
Also, there is a text file describing what was done, and the frames numbers where the downshifts failed. (Tried to slap together the info in an easily digestible form)

This is the second trans that was put in (a built 4l60e), in an effort to solve this issue.

Any feedback from some experts would save the day!

The car?
1998 Pontiac Formula
FLT Stage IV trans (vacuum modulated) , Vig 3600 converter, Stage II heads, 236/240 .591 cam and assorted goodies.
The PCM has already been replaced once cuz we thought that was the problem.

(Ignore the sig..thats the old setup..)

SSpdDmon

iTrader: (10)

Hmmmm....vacuum modulated....I'd say it's a problem with the vacuum line (or the hardware) and not the PCM.

DóòD

The modulator was removed for testing..the problem still persisted so it was slapped back in..

SSpdDmon

iTrader: (10)

Maybe I'm misunderstanding. I thought a VM trans worked like they used to on cars without computers...by referencing manifold vacuum to know when to shift. Am I wrong?

DóòD

Heck if I know.. thats why I'm posting this..

This has been a persistent problem for a while.
I bit the bullet and picked up HPtuners to see if it could be tweaked.
For the last week I've been haunting a few forums trying to find some holy grail fix that would solve this.

foff667

iTrader: (2)

Throwing any codes? I would say Try disabling the p0121 diag. test under engine diag-tps sensor and see if it still occurs. Does it happen only while rolling or from a dead stop as well?

DóòD

No codes were picked up during the logging, at least when I was pulling DTC and trying drive at the same time...(log included in the zip file in the link)
If you look at the log, TPS seemed to be recording/performing fine.. Also, the TPS sensor was replaced previously.

Yes, it happens from both a roll and from a dead stop with the 'regular tune'.
But the tune that prevents a 3-4 shift till 40mph seems to allow a decent launch. (I think I need new tires testing THAT one earlier this week.. )

DrkPhx

iTrader: (15)

The vacuum modulator is mostly used to control line pressure and shift speed. The PCM still controls all other aspects of the trans calibration including the TCC apply and release tables.

Dood - I run the same trans and a Yank PT4000. More than likely it's in the tuning. My setup took significant tuning of all tables to make it driveable. I even created an Excel Spreadsheet to compare the various part throttle and TCC Apply/Release tables to help pinpoint problem areas.

Anyway, it sounds like there are two separate issues. My guess it's the TCC release tables for both 3rd and 4th gear. I would also lower the values by 20 kPa in both the TPS Test Min and Max tables.

DóòD

I had a yank4000 before the vig3600. It had the same problem. Thinking it was the converter, THAT was replaced too. (Altho when returned to Yank they said they cracked it open and found a problem, no charge on the rebuild, but I lost big cash selling a basically new converter with only 250 miles on)

Ive heard from various sources that 98's, on occasion, seem to have this problem.
But the car was a monster with the previous stock trans/vig3200/3washer shift kit combo. It shifted great!

Lower the values in the TPS Test Min And max tables? I dont understand that.

This excel spreadsheet? Would you be willing to impart some of this wisdom on a newbie at this trans stuff and perhaps end the months and months and months of suffering I've gone thru with this issue?

foff667

iTrader: (2)

He's referring to the same tables I told you to go to and disable.

Frost

iTrader: (45)

I recently tuned a 98 with this problem and it is on-going... I'll edit this post in a second with the threads that show my attempt to glean understanding with the issue.

foff667

iTrader: (2)

Yours is slightly different in that he said his wont shift right from a stop whereas yours just wouldnt downshift properly.

When I had my 98 I had a similar issue where it would go from 1st to 4th gear by 35mph at wot after I installed my heads/cam. I turned off the tps diag and all was well.

DóòD

Well..thats exactly what it did with the 3200vig, the 4000yank and the now installed 3600vig.
It would shift from 1st to 4th.
Heck..it happend on the track with the yank. It was really embarrasing too.

If you look at the tune I'm using now, it will NEVER shift into 4th until 38/40 mph. That seemed to mitigate the problem but it still exists.

So...turning off the tps diag (p0121 diag) did the trick for you?!?!
Your kidding? I only WISH it would be that simple!
I'll reflash to the 'normalized' shift tables and disable that code as soon as I get home from work today!
If that works? I'll...well... I'd...Ummm (Well, lets see if it works first.. )
Lets put it this way, the next move (and next two fistfuls of cash) would be to go with that TCI transmission control unit. I certainly dont want to have to go that far.

Sorry..I'm corn-fused. This is disabling the code rather than disabling a 'table'... right?
And "Lower the values in the TPS Test Min And max table" as stated...I found no relational tables described that way..(In HPtuners anyway.)

foff667

iTrader: (2)

I've set the test to disable in this file http://www.thetuningdoctor.com/HPTun...forlogging.bin please use the compare feature to see what I did so YOU know for your own reference in the future. Hopefully this cures your issue as it did mine, I know how embarrassing it can be to loose to a honda with your heads/cam/stalled LS1

DóòD

Oooh...Ok..
I was thinking it was just a checkbox setting in the DTC listing..
But you set:
P0121 Error Max MAP 100kPa
P0121 Error Min MAP 0kPa

foff667

iTrader: (2)

Correct, this disables the sanity check basically. Larger cammed cars/trucks will sometimes go outside of these boundries. On M6 cars its not so much of an issue but on A4's it can wreak havoc.

Frost

iTrader: (45)

Bill I haven't seen this before, could this possibly be related to my non-downshifting tranny?

DóòD

I'm gonna try this when I get home...(Altho I have to head out very quickly after I get home, I will definitely report the results as soon as I can!)

I hope it works.. Granted, I havent thrown any codes, or at least saw them when scanning, but if it works... well, lets see if it works. I can't get too excited. I've had too many 'close call fixes' that I'm very jaded about this thing ever downshifting correctly..

DrkPhx

iTrader: (15)

I had the same problem and changing the TPS Min/Max tables fixed it.

DóòD

In going thru my tune I saw that the EGR was still enabled...weird. (I have an LS6 intake w/no egr).
I just killed it..
Under engine-->General
EGR Enabled = Disabled
Diag disable Speed = 255
Diag Enable Speed = 255

I figure The air pump should go bye bye too with the LS6 Intake on a 98 right?
So..
Air Pump
Disable ECT = 284

Does that seem about right?

I mention this because I thought that perhaps that Even tho the EGR and AIR DTC are not reporting (for emissions testing) that the because it was still enabled, it could be making the PCM wacky. Basically it may be gen'ing alot of codes, but not reporting them. Mehhh.. Its just a thought.