Volvo Maintenance Hints for 7xx/9xx - Bill Garland's Nuclear ...

Although strong solvents instantly dissolve gum, varnish and carbon from throttle
plates and bores, they also dissolve throttle shaft seals, throttle position sensors or
(when applicable) the Teflon from the air inlet horn! Nevertheless, specially formulated
throttle body solvents do as good of a job without causing potential driveability
complaints. Most are also good for cleaning delicate import carburetors for the same
reason. Unlike "killer" carb cleaners, throttle body solvents don’t cause comebacks by
eating away at delicate switches, potentiometers and neoprene diaphragms found on
import carburetors. Most throttle-body aerosols also spray in the inverted position for
cleaning hard-to-reach components.
Cleaning Procedure. [llustration copyright RPR, used by permission]
❍ Disconnect the wiring harness from
the throttle switch by compressing the
wire bail on the connector body, then
pulling the connector straight away.
❍ Disconnect the three rubber vacuum
lines. Two have spring hose clips
which must be compressed to loosen
and pull off.
❍ Disconnect the throttle actuator rod
by using a small flat-bladed
screwdriver to gently pry away the
little locking tab on the end of the
lower ball-and-socket. Use a flashlight to see it better. (The plastic ends
which have the socket & ball attachment on the link rod can break when
they are removed from an old or very cold engine, so be very gentle and
don't work on a frigid piece of cold plastic. Get replacements from the
dealer. One is a right-hand thread, the other left-hand.)
❍ Unscrew the three nuts holding the TB on to the intake manifold. You
may need a magnet here if you drop one.
❍ Remove the throttle body from the intake manifold. The gasket on my car
lifted right off with no fuss, but if you have to scrape be sure to use a
plastic or wood scraper so as not to damage the aluminum facing. You
can reuse the gasket if it is in good shape. Better to replace it if old.
❍ Clean the entire throat and the throttle plate paying particular attention to
the edges and pivot points to make sure it can close completely. Use an
old tooth brush and spray fuel injection (not carburetor) cleaner. Don't
spray the cleaner on the black plastic TPS. Remove the base idle black
adjusting knob if so equipped and blow out that passageway and blow
out another bypassing passageway that you will see in the throat. [Norm
Cook] If you don't have compressed air, take this base idle boss off and