High idle disappears when I unplug the IAC valve, but it is brand new

[SenorNoob]

Surging only in neutral with a manual? On a 91? Is the neutral safety switch (It should be in the transmission. NOT the clutch switch. They share a wire color.) hooked up and working?

 

[jcook100]

Surging only in neutral with a manual? On a 91? Is the neutral safety switch (It should be in the transmission. NOT the clutch switch. They share a wire color.) hooked up and working?

That is a good question. In fact, awhile back when I did the EEC-IV test, I did see a code pop up for the neutral safety switch.

Take a look at these photos. I only see one switch that is "plugged in" - air quotes because it looks to be partially smashed and just barely connected. Is that the neutral safety switch? Or maybe the reverse light switch, or something else? It is on the driver's side. The pins are cylindrical (Pic 2) and the two wires are purple with an orange stripe and black with a pink stripe.

Strangely, there is a connector that branches off of the wiring for the first switch that I mentioned that is just hanging there unplugged (see Pic 1). Any idea what that is the connector to? On the passenger's side of the transmission there is what may be another mangled plug of some type. It almost just looks like a bolt, but the inside appears to be broken plastic (see other pic). Maybe this is what the other connector is supposed to connect to?

 

[jcook100]

@SenorNoob Any chance you could provide your feedback on this?

 

[SenorNoob]

Sorry I haven't been at my computer for awhile. The red one is the reverse light switch. The other is the neutral switch. I've heard that they are unavailable new. Certainly not on O'Reilly or Rockauto website. Also heard that the reverse switch fits in the same place. Just have to change the connector. I have not tried it.

 

[drewmart00]

@jcook100 do you have any other updates? Have you fixed the problem on your truck?

 

[Mister G]

Just because it's a "NEW" part doesn't mean it's a "GOOD" part. I've taken back several "NEW" parts that were no good!

I second that, same here. Stick with Motorcraft parts.