99+ Y87 lag programming....

[Guardsman]

I was reading in the database that 99+ Y87s had reprogamming available to get rid of a lag. When I go to WOT from freeway speeds, the car starts to accelerate a bit, then all of a sudden, it's like something kicks in, and it takes off. Is this the lag, and if so, do the GM dealerships have to do this programming for free, or do we have to pay to get it done? Thanks.

[OnixV6]

<blockquote>quote:</font><hr>Originally posted by Guardsman:
When I go to WOT from freeway speeds, the car starts to accelerate a bit, then all of a sudden, it's like something kicks in, and it takes off.<hr></blockquote>

i believe that would be your auto tranny downshifting.

[Guardsman]

No, this is after the downshift. It downshifts, begins to accelerate slowly, and then it suddenly picks up, it feels like somebody's rolling in more throttle. I don't know if it's maybe the PCM advancing the timing, or kicking in more fuel, or what.

[strange_trp]

i think this is due to a temporary delay in the Throttle Actuator Control system, since the 99+ are throttle-by-wire systems. could be a lazy accel pedal sensor, could be a lazy stepper motor in the TAC unit (throttle body).

i would also check TP sensor to rule out. checking voltage drop across sensor with analog volt meter or oscilloscope (DC volts) while an assistant SLOWLY depresses the accelerator pedal, you should get nearly 0 volts at closed throttle and nearly 5 volts at WOT, with a very smooth curve in between (i suggest analog meter or scope so you can observe glitches in sensor signal.)

improper valve timing or exhaust system restrictions may also be other causes of this type of hesitation.

and it very well may be that this is normal system operation. as your rpm's increase, your engine will produce HP and TQ at a greater rate (to a point). check out the HP and TQ curves for your engine. mine feels like it pulls hardest between about 4-5.5k rpm, and starting at about 2k rpm it feels like it steadily builds up to its max power output. this is normal.
although altering signals to PCM to let the TAC do its job more efficiently is not a bad idea....

a flat torque curve is a powertrain engineers wet dream.

[Guardsman]

Here's the section from the tech database:
"For Y87 automatics, there is a PCM update from GM that will "correct throttle lag during heavy acceleration". For non-Y87 automatics and all manuals there is no correction because GM decided that there is no need for one."
So, it shouldn't be throttle related, because it's auto-only, so maybe it's a tranny or timing issue? Does anybody know for sure, or know where to find out?

[ July 01, 2002: Message edited by: Guardsman ]</p>

[99Camaro99]

so where would you get this fix/updated and would it be free?

[Guardsman]

Anybody???

[knowledgefreak]

or maybe whoever put that in the database has no clue...

[DeathBuzzz]

For non-Y87 automatics and all manuals there is no correction because GM decided that there is no need for one.

I have a 99 and have no idea what you are talking about. If i goto WOT my car will downshift and go. If there is any lag at all it is hardly noticeable. How much of a lag are we talking about here? More than 1 sec?

~Brian

[Guardsman]

It's about a 1 second lag, it's very noticeable. It's not shifting gears, it's almost like maybe it goes to part throttle, downshifts, and begins to accelerate, then kicks in the rest of the throttle.

[bu-bye]

My car has no lag but I am very interested in this update you speek of. Is it at any GM dealer?

[Guardsman]

That's what I'm trying to find out.

[imported_admin]

<blockquote>quote:</font><hr>Originally posted by knowledgefreak:
or maybe whoever put that in the database has no clue...<hr></blockquote>

THAT'S IT. KNOWLEDGEFREAK, YOU ARE NOW PERMANENTLY BANNED.

:mad: :mad: :mad:

I am SICK AND TIRED of warning you again and again about your snide remarks and attitude problem. Steve just unbanned you a few days ago from sticking your foot in your mouth from last week, then turn around and insult the person who spent MUCH MORE TIME AND ENERGY on the Tech Database than you would ever do to help your fellow F-Body owner. My mommy taught me if I can't think of anything to say to keep my mouth shut. Apparently you never learned that. With that regard, go away.

The tech database is correct. Dealerships do that PCM programming for free, it is considered a recall. It applies only to 99 automatics with Y87--so Guardsman, that's you. Mike Wenski was the authority on this PCM update, contact him for further details, though any decent GM dealer should have the info available. Any GM dealer can do the program assuming they know it exists.

[ July 09, 2002: Message edited by: Stefan ]</p>

[imported_admin]

P.S. Anyone who starts a flame war over knowledgefreak and his attitude-problem-laced-posts will also be immediately and permanently banned. Consider this a warning in advance.

[99Camaro99]

so way stefan back on to topic.

THere is a PROBLEM with 99 Y87 automatic F-bodies with a throttle lag? And you are saying that if I bring it to a dealership they should be able to PCM program this correctly.

If I were to do this, how could I prove it to a service manager. Is there some "GM Database" that says this. Not flaming, but I want this corrected and I would like to know how to go about doing this.