Throttle Body maintenance 101:
READ THESE INSTRUCTIONS ENTIRELY
BEFORE STARTING THIS PROJECT!
(YOU WILL NEED A DIGITAL MULTIMETER
IF YOU TAKE THE TPS OFF! DON’T ATTEMPT TO REMOVE THE TPS IF YOU
DON’T HAVE ONE, IT IS MANDATORY!)
You should also buy the
gasket kit from GM that includes the 4 gaskets and costs about $25.
Using your screwdriver remove the air duct in front of the
throttle body, now open the throttle by hand (engine off of course) and
feel behind the throttle blades. Did your fingers go all black and gungy
(yucky isn\’t it). You need to get that throttle body off and scrub it
cleaner than clean can be.
Preparation: Go and buy some throttle
body cleaner (NOT CARBURETOR CLEANER), and buy yourself a new toothbrush,
your old one just got a new life.
Get an old bowl or something
similar, rags and perhaps some of those lovely rubber surgical gloves.
Getting right on in there remove the 3 pin connector from the throttle
position sensor, and remove all the pipe work going to the throttle body,
there is a little water spillage, not much. Also remove the IAC connector
(a 4 wire square connector) it\’s a bit fiddly to get to.
tricky part, the throttle cables need to be released, (manual and auto
cars are different), the cables are fixed with wonderful things called
Jesus clips, you slide a screwdriver under it and ping it disappears, you
mutter \’Jesus where did that go\’ – what a name for an item. Best to
cover the area with a cloth to capture any pinging that goes on.
the cables released the throttle body should be free to remove. Undo the
four long bolts holding it to the plenum, careful when prizing it apart,
do not damage the gasket unless you are replacing it. Now you thought you
were clear didn\’t you, nope, GM put a little booby trap underneath.
There is a small vacuum tube with a rubber elbow that needs to be pulled
off, be careful with this hose, they tend to get brittle and break with
age. You\’re free!
Now comes the really dirty part. Put the
throttle body in the bowl and spray with throttle body cleaner and scrub
like crazy, especially around the throttle blades. Its great, really messy
but the final spray just cleans it all off and there you have a gleaming
Now using a 30-32mm spanner remove the IAC valve
(that\’s the large black looking thing on the side), mind the gasket.
Clean the spring and pintle and if you can get inside the orifice and
clean the seat area. Make sure that the small hole going from the throttle
mouth to the IAC is clear. Finally just spray the spring and pintle with
WD40 and replace the IAC valve.
Final check – and perhaps another
blast with the cleaner to remove any surface muck still there. You may
want to soak a rag with throttle body cleaner and clean as far in the
plenum as you can get. Allow to dry and replace the throttle body on the
plenum, taking great care with the gasket ensure it is positioned
correctly. Ensure all the connectors cables and pipes are back on
(don\’t forget the little tube underneath).
This may be a good
point to check and adjust your throttle position sensor. Get two paper
clips, straighten out and slide into the end of the TPS sensor connector,
A (earth) and B (tps output), keep the wires separate and turn the
ignition on (car off) and measure the voltage at the wires and adjust by
loosening the torx bolts, if necessary, to 0.54 volts – this is the normal
Self satisfaction. Job done now you should start
your Corvette and stand back to admire the even tickover and you will
marvel at the smooth response the car now seems to have. If nothing else
you have pampered and tinkered for about an hour, got filthy, therefore
justifying your time and got a tangible result afterwards, all that
remains to do is test drive the car to the nearest (or in fact not so
nearest pub). Congratulate yourself with a beer and apply wide beaming
Throttle Body maintenance 101: