Re: High idling 86 5kt

[Dave Head <dhead@sundial.net>]

At 01:43 PM 3/23/97 -0600, you wrote:
>Yes, that is it Dave, exactly!! Where is the decel valve?
>
>David.
>
>PS. By the way due to your help I was able to get the check pad light off.
>It turned out the wire was broken up towards the wheel well on front drivers
>side.

Great - wish I could find where mine's broke!

The decel valve is hard to find - it's buried under the FI stuff, behind the
airbox. But you can listen for it.

I can already tell you 90% certainty yer problem is the throttle switch
bolted on the side of the throttle body. black case with plug going into it
- right next to where the metal tube for the turbo makes its bend. Inside
the case (glued shut) is a microswitch and a leaf switch. The microswitch
controls the decel valve - when you shut the throttle, it closes the
microswitch contact, sending a signal to the ECU - at any engine speed above
1200 rpm, the signal is passed to the decel valve, causing it to open. This
results in a 'sucking sound' for a second or so, each time you blip the
throttle above 1200 rpm. 
The decel valve bypasses air around the air flow sensor plate, allowing the
plate to drop - at 1200 rpm, the decel valve closes, allowing the sensor
plate to slowly lower back to the idle (rest) position. 

When de microswitch no workee, the sensor plate hangs wherever it feels
comfy at any given moment, allowing your extreme embarassment as you are
sitting at the light next to the Mustang GT idleing comfortably at 2600 rpm.

Sometimes it is just a bad solder joint, other time the microwitch has gone
south. The microswitch can be had at any electronics store for 3.00 or so -
you have to glue it in place after you muscle the cover to the unit off.
Score the seams on the sides with a single edge razor blade, then use a
small screwdriver to pry it open.

Other option is to buy it from the dealer - I believe 65.00 discounted.
While yer in there you can verify operation of the leaf switch - it gives
you a preset rich fuel value when you nails de phoot down...
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                                   EMCM(SW) Dave Head  
87 5KCStq 188K miles                               1.7 bar 
                                        Maitland, Florida   
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