OK, i know many of you have heard of the seafoam treatment that can be done to de-carbonize( if there is such a term) that will improve performance,
I just did this treatment using the deep-creep method( a spray version of seafoam), and yes it has made a differance, no more pinging ( timeing was set at 6* BTC ) engine vibration is now much less noticeable, aven smoother idleing, and smooth quick starting.

my question however is having done this i now notice a very strong jump in the power band at around 2600 rpm but only under 1/2+ to 3/4 throttle and it is very abrupt when it happens, almost like 2 more cylinders kicking in ( and no... there is no miss or skip to the engine at any rpm), or the transmission downshifting ( tried same test in manual shift mode with the same results). It is very noticable when it happens, and it never happens with less than 1/2 throttle setting.

I wonder if maybe my TCC is continiously locked and is simply unlocking when vacuum /rpm reaches a set point? I say this because i have never noticed TCC lockup/disengage at any other speeds other than... well lets just say in excess of 80+mph.

and the seafoam treatment has simply made this very noticable now.
and yes it pulls like a stump puller now.

BTW it is an 87 w/ 100k and TH700r4 trans rebuilt less than a year ago.
anyone with any ideas as to what is causeing this JUMP in pulling power?

 

Larry,


I dont have any help for you but Question.......Ive done seafoam on other cars but never on the vette because of the intake angle.......dod you spray it in????

 

I believe your torque convertor is fully electric as far as lock/unlock goes. You may want to put a multimeter on your throttle position sensor (TPS) and make sure it is in the .54 range at idle and close to 4.5v at full throttle.

What you may be feeling going over 1/2 throttle is the car going into what is referred to as WOT or PE mode (Wide Open Throttle or Power Enrichment). This is when the ECM sees the TPS at a certain voltage (I think 3.69v for your '87) and says "ok momma this guy wants all we got" and advances the timing and modifies the fuel curve for maximum power.

What is has to do with 2600 RPM I have no clue about. :lol:

 

My95:
Yes, i used Deep Creep and sprayed it into the PCV Line until the engine started to load up ( and smoke very heavily ).

Just a note the engine will surge in RPM as you start spraying, so i put it into Diag Mode, disconnected the IAC then sprayed it into the PCV Line ( make sure you plug off as much of the vacuum leak as possible when doing it )

Scorp:
well the 2600 rpm may actually have nothing to do with it.. other than thats about where it is when it hits that "PE" point.
I will re-check the TPS settings



[Modified by LarryK 87, 2:18 PM 7/5/2003]

 

yeah....its amazing how much smokin that stuff will do.....I think Im gonna do mine