89 GT idle adjust? IAC spacer

After replaced IAC still wouldnt idle so installed IAC spacer and it
runs pretty good at 12 BTDC, TPS is set low, fuel pressure about 35-40
psi.

Only thing now is when stopping, put the clutch in and brake, when the
RPMs hit bottom it will die if I dont feather the gas. Tried to adjust
IAC spacer screws to let more air in but then the idle gets worse.

89 GT 5spd, Trick flow heads and cam, BBKSSI Intake, BBK cold air,
Ford Racing throttle body, vacuum resivior

sounds like a vacuum leak.

wrote:
> After replaced IAC still wouldnt idle so installed IAC spacer and it
> runs pretty good at 12 BTDC, TPS is set low, fuel pressure about 35-40
> psi.
>
> Only thing now is when stopping, put the clutch in and brake, when the
> RPMs hit bottom it will die if I dont feather the gas. Tried to adjust
> IAC spacer screws to let more air in but then the idle gets worse.
>
> 89 GT 5spd, Trick flow heads and cam, BBKSSI Intake, BBK cold air,
> Ford Racing throttle body, vacuum resivior
>

> wrote in message
...
> After replaced IAC still wouldnt idle so installed IAC spacer and it
> runs pretty good at 12 BTDC, TPS is set low, fuel pressure about 35-40
> psi.
>
> Only thing now is when stopping, put the clutch in and brake, when the
> RPMs hit bottom it will die if I dont feather the gas. Tried to adjust
> IAC spacer screws to let more air in but then the idle gets worse.
>
> 89 GT 5spd, Trick flow heads and cam, BBKSSI Intake, BBK cold air,
> Ford Racing throttle body, vacuum resivior
>

sounds like you are close. Typically with it dying like that it would be the
IAC clean or replace. The signal to it should be a square wave, forgot what
the frequency is, but they vary the duty cycle to get it to open more or
less. I would think that one lead would be signal and the other ground,
rather than getting it off the block.
How are the HELO sensors in the exaust? they can get contaminated if you
use silicon gasket material. You should be working closed loop. Good luck,
and let us know what you find.

Well, replaced the IAC with no spacer, no good, added spacer, then
better. We figured out that the IAC holes on the new ford racing
throttlebody are smaller than stock!!! couldnt beleive it, put the
stock TB on and now it idles, though rumbly because of the heads and
cam. it looks totally sweet and hauls a55 too. still have to try a BBK
70mm TB and get the smog pump pipe welded shut on the exhaust and see
how much better it gets. but its definately a highly modified stang
now.

So Id have to say there is something to those IAC spacers, FR TBs
suck, and the bbkssi intake probly outperforms the trick flow and
looks totally killer but its a totall PITA to install. though like
anything, once your done and familiar with all the solutions you came
up with you can tear it down and put back together almost blindfolded.