cruise and shift light problem

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Stacey Slinkard - 10 May 2006 14:52 GMT

I just bought an 87 SE, and the cruise and shift light worked fine when I
first drove it, and the next day neither worked. Haven't had time to do
mush checking, but all the fuses are okay. I suspect a vacuum leak
somewhere. Anyone have any suggestion where to start?

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gw - 10 May 2006 15:52 GMT

Does the speedometer work? Is the Check Engine light on?

Vacuum leak usually results in a high idle.

>I just bought an 87 SE, and the cruise and shift light worked fine when I
>first drove it, and the next day neither worked. Haven't had time to do
>mush checking, but all the fuses are okay. I suspect a vacuum leak
>somewhere. Anyone have any suggestion where to start?

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Stacey Slinkard - 11 May 2006 13:59 GMT

the speedo works fine, the tach has cut out briefly a few times, and the
idle is erratic at times also. the check engine light is not on.

> Does the speedometer work? Is the Check Engine light on?
>
[quoted text clipped - 4 lines]
>>mush checking, but all the fuses are okay. I suspect a vacuum leak
>>somewhere. Anyone have any suggestion where to start?

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gw - 11 May 2006 15:47 GMT

Curious. The shift light is triggered by the ECM based on vehicle speed (VSS
sensor), throttle position (TPS sensor), coolant temp, and RPM from the
distributor. I don't think it cares about vacuum.

If you have a 4 cyl, cruise control is through the ECM. If it's a V6, there
is a separate module behind the dash. Both rely on VSS input from the speedo
for vehicle speed.

The only common point in the two problems is the VSS, but your speedo is
working. Take a look here for cruise control troubleshooting:

http://www.fierofocus.com/articles/Tech%20Tip%20-%20Cruise%20Control.htm

> the speedo works fine, the tach has cut out briefly a few times, and the
> idle is erratic at times also. the check engine light is not on.
[quoted text clipped - 6 lines]
>>>mush checking, but all the fuses are okay. I suspect a vacuum leak
>>>somewhere. Anyone have any suggestion where to start?

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