85 Fiero GT Idle Speed Too High

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Jim Vanderpool - 28 Mar 2005 16:58 GMT

Hi, 03/28/05
I would appreciate any help with the following problem I have with my
1985 Fiero GT. It is a V6, automatic with A/C. It will idle above 2000
rpm even after warming up. It has around 87,000 miles and it sits most
of the time since I live in Western New York and the climate isn't the
best for driving old cars. I would like to offer thanks in advance for
any help that is offered.
Jim

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Phil Randolph - 28 Mar 2005 18:27 GMT

Sounds like a vacuum leak - one of the most common places is a crack in
the tube leading from the EGR valve to the intake plenum

> Hi, 03/28/05
> I would appreciate any help with the following problem I have with my
[quoted text clipped - 4 lines]
> any help that is offered.
> Jim

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Execulink Newsgroups - 21 Jul 2005 08:13 GMT

On my 1985 GT there is a set screw on the top of the throttle body assembly
that appears to be intended for the original OEM setup of the thottle body.
It controls how "open" will be the the door assembly in the throttle body
that regulates airflow, as well as the throttle position at idle, from what
I can tell. In my experience it can be used to adjust the idle of the car;
whether this is a prim and proper use of it I cannot say.

In any event, if it was turned at some point, this can force the car to idle
high and never go off what seems like high idle. You might try letting the
car warm to operating temp then adjusting it to rated idle when warm. On my
1985 GT this seems to be around 800 RPM. MArk the original position of the
screw, however.

K.E. R.

> Hi, 03/28/05
> I would appreciate any help with the following problem I have with my
[quoted text clipped - 4 lines]
> any help that is offered.
> Jim

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JazzMan - 22 Jul 2005 01:45 GMT

That screw is a throttle stop, not an idle adjustment. The
actual adjustment is done with the IAC by the ECM. The IAC
is a stepper screw with a pintle that seats in a bore in
the bottom of the throttle body. The ECM turns the stepper
motor shaft screw as needed to bleed air into the intake,
this bleed air actually is what allows the car to idle.

If it is tampered with, usually by people trying to deal
with another unrelated idle issue such as caused by a vacuum
leak, the only way to bring it back to proper adjustment
requires looking at the IAC counts in the ECM data stream and
adjusting the stop until the counts read 16-20 with the engine
warmed up, A/C and radiator fan off.

JazzMan

> On my 1985 GT there is a set screw on the top of the throttle body assembly
> that appears to be intended for the original OEM setup of the thottle body.
[quoted text clipped - 19 lines]
> > any help that is offered.
> > Jim

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