Got it. Thanks.
Somewhere I heard or read that one way to test your ISV was to disconnect
the power to it when the car was running. I think the point was, if there's
no change then you have a bad one. It might have been this newsgroup even
where I read this test. I did that test today and it made no difference. I
have cleaned the unit before as well.
I'm going to have the voltage on the O2 sensor next week from a cold start,
and I ask them to check the MFTS too.
b4 you worry about the O2 sensor you should check whether the idle
switch on the throttle body is working and telling the ECU to operate
The idle switch and the WOT (wide open throttle) switch are both in the
throttle body between the rubber intake boot and the intake manifold. It
is the place that the throttle linkage goes to and moves the throttle
plate when you push on the gas peddle. You are probably completely aware
of this but just in case...
On the back of the Throttle body there is an electrical plug easily
accessible that contains three wires. This plug takes signals from the
switches to the ECU. Use an Ohm meter to test between these contacts
(going back to the throttle body) to confirm that when the linkage is
closed (idle) that one of the pairs of contacts changes from open to a
closed circuit. This will change just a VERY small distance b4 the
linkage closes. If this change occurs then the switch is operating,
telling the ECU to ISV and the problem is elsewhere.
OTOH, if the switch does not go to a closed circuit when the linkage is
closed then the ECU has no information to operate the ISV.
- There is a threaded screw and locking nut that operate as a stop on
the linkage. Try to back this off a bit (very little at a time) to see
if closing the linkage will now close the circuit. Sometimes the linkage
gets dirty and corroded by the return coil spring. You can try WD40 to
loosen this up and then carb cleaner to remove the WD40. Lubricant on
this can gather dirt and make the problem worse. Also try to close the
linkage with your hand with a little force to see if the contact on the
idle switch can be made. This worked for me on my current type 44 but
that was to correct a low idle problem.
If this doesn't help : (
- The idle switches on pre '91 years have a tendency to crack their
contacts even though they are soldered. I think that you need to open
the throttle body to get at the switch. try to re solder the joints.
Works for some people. Others replace the switch from a 'donor car' with
a known good switch.
'91 100q 5spd
Bill Graham wrote:
Thanks for all the effort on this post Tony.
I know what you're talking about. I was planning on replacing the throttle
control switch anyway. They're on $41.00 and was informed this is a must-fix
before making any boost/ECU/wastegate upgrades.
I believe that the threaded screw and locking nut on the linkage is at the
back of the linkage on the right side of the throttle body (facing the car).
It's pretty corroded looking back there. I'll clean it all off and the
proceed with that.
On another brief note: when it gets a little warmer here (I have to work on
the car out in the driveway) I was planning on going through the whole
engine compartment and cleaning all electrical connections. Then applying
some dialectic grease to the points to keep them somewhat insulated. This
procedure was an advised one here:
Do you support this process?
Thanks again. I've got plenty of things to try now. I really appreciate it.
Yes, checking all the connections is a good idea. I use DeOxit from Caig
Labe to clean them. Radio Shack CRC tuner cleaner works fine too. A
dielectric protective grease is a good idea but if it is too conductive
it could cause a problem if bridged between adjoining conductors.
I had a problem on a previous '87q that turned out to be the connections
on the knock sensor having become bad. cleaned and re-connected.
'91 100q 5spd
Bill Graham wrote:
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