Is it possable to have vacuum high enough to hold the throttle plates slightly open during de-accelleration on the road and have a high idle until I "kick it down"?

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86 Camaro Sport
383 Speed-O-Motive Crate Engine, Trick Flow Heads, 58mm Accel TB, 3.73 Auburn Pro, SLP Cold Air Induction and Headers, Dynomax Cat-back, Serpentine belt setup, Dual IROC Fans.

http://www.sethirdgen.org/octride.htm

 

What is your vacuum during de-acceleration? Normal is between 18-22" Hg. It is usually higher for decell because the engine is turning faster, but the throttle is still closed, hence, more vacuum. It would be interesting to see what your vacuum is, I am sure that 383 w/ high flow heads sucks in quite a bit of air! (even with the stock intake).

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ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey,
22# injectors,
JET AFPR,
Ported Plenum,
TB Coolant Bypass,
SSM SFC,
Boxed LCAs,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
KYB Shocks

'97 Bonneville SSE

 

Actually, you know what, try this, John. Hook up your Diacom, get it to do it, monitor your TPS (was like 3% right?) Cut the car off and turn the ignition back on (don't restart it) and see what your TPS is then. If it is still 3% with the car not running, then its something else. If it goes down, then your theory is probably right.

------------------
If you live in Southeastern US, check us out!
South East Thirdgen


ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey,
22# injectors,
JET AFPR,
Ported Plenum,
TB Coolant Bypass,
SSM SFC,
Boxed LCAs,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
KYB Shocks

'97 Bonneville SSE

 

And just to add to GMT's advice, if the throttle plates are truly sticking open a bit, you might want to inspect hte throttle body and plates closely for interference. If the shaft bushings are worn, or if the plate mounting screws have been loosened somehow, the plates may not be correctly aligned with the bores. This can lead to the throttle sticking at various points near closed throttle, causing a "variable" idle speed every time you let the throttle relax. the change in TPS might also be a good diagnostic for this condition.

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Later,
Vader
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