kent

A friend and I install a ported and polished throttle body on my car today. After completion of the installation, we notice the plate/butterfly only opened 75/80 percent. <img border="0" title="" alt="[Mad]" src="gr_images/icons/mad.gif" /> We could not figure out what was wrong and figured the P and P Throttle body was bad. So we reinstalled the stock throttle body and notice the butterfly/plate did the same thing. <img border="0" title="" alt="[Mad]" src="gr_images/icons/mad.gif" /> The throttle cable somehow had got stretch and consequently the butterfly would not opened completely. We finally figure out a way to tightened the cable by placing a rubber hose on the little wheel assembly with the cable inside the rubber hose and adjustment of the cable with the cable adjustment. My question is, if the butterfly only opens 75/80 percent of the way, is this costing me 60'time, ET, and MPH at the track? <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> Your assistance with this question will be appreciated.

WILWAXU

iTrader: (6)

ttt

gwj

Is the 75% based on the reading from the TPS or eyeballing? The reason I ask is any TPS voltage over about 4.0 V will usually read as 100% throttle by the pcm. If you make any adjustments you need to track the TPS voltage; 4.75V will set a code. If you're not quite at 90* with the TB blade @ WOT you could grind the bumpstop a little, being careful to monitor the TPS Voltage.
As an example, when I checked my TB the blade was obviously not opening to 90*. Before I ground the bumpstop it was at 4.36V: after, 4.60V.
Hope this helps.

jimmyblue

iTrader: (11)

I don't see how you could stretch a steel
throttle cable enough to lose that much (1/2"?)
draw. You should check the pedal, that there
is nothing interfering with flooring it
(like bunched carpet, floor mats) and that
the cable end appears all right - no lost
little plastic spacers, etc.). The cable
should have the barest minimum of slack at
rest (idle). If there is no slack then it's
a lever arm draw issue with the pedal. You can
get more pedal travel by removing the pedal
from the car and putting more of a bend in
the steel rod. This seems to be pretty hard
steel, so it's not likely to have gone bad
and might take some persuasion to bend more.
The pedal runs pretty close to the transmission
tunnel hump and aftermarket pedals might give
a bind, too.

Some cars I've seen two mounting holes for the
cable on the pedal arm - the one nearest the end
gives the most butterfly movement for the least
pedal travel. I don't know why there's be a use
for the other one. But this is older cars where
you could see 4 different motors and 6 different
carbs. Just a thought; might peel off the plastic
and check it out.

It seems to me that you would want to grind
the bump stop (or, just bend the stop tang)
for 99% physical open, and then rework the
TPS for electrical alignment if it's over-
the-top. Reworking metal for electrical output
is a secondhand thing.

You don't want the butterfly to go over center.
because if it's at all asymmetric then airflow
force may fight the return spring. But you do
want the plate to present minimum cross section.

Get the physical air path optimized first, and
then true up the electrical representation if
needed.

By tangentially slotting the mounting holes on
the TPS potentiometer (and possibly reworking
any locating pins, if needed) you can get some
rotational alignment adjustment freedom.

itSStock

Common problem with cruise control cars...time to reset...

Jantzer98SS

iTrader: (54)

Kent,

Make sure it's not the TB itself. Here are a couple things to think about.

Is the TB accelerator hitting the bump stop now, which isn't opened all the way. If so, it's normal and you just need to do the TB bump-stop mod. Does the new TB have the correct TB accelerator (shaft) they are different from 98/99 to 00+ that would cause what you describe. The earlier are rounder and later being more aggressive more oval looking.

The cable doesn't stretch a 1/2 inch in the time it takes you to swap TB's. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

kent

Thanks for the replies. Next weekend I may work on the car, but for now, I just don't feel like it. I went to the track and I was disappointed, not the results I expected. Sometime, in the future, I will review all recommendations and suggestions and go at it again. I have no device to determine the voltage on sensor, I just eye-balled it. I am seriously thinking of having my own TB port and polish and retry again. Anyway, thanks for the assistance.

gwj

I used a voltmeter to spec mine out. You can get a cheap one just about anywhere. Just get some small solid wire (like telephone wire) and push down next to the wires at the TPS connector. I think the blue and black wires are the Potentiometer wiper.

kent

Thanks GWI.