Quick question: what's this switch?

[Redsquall]

Would I affect hot or cold idling chuggyness?41868

[jangell]

The wide open throttle (WOT) microswitch. There are two of them on an automatic, with the second one used to kick the transmission down a gear when you slam on the gas. I think the other one changes how the ECU delivers fuel/spark when the pedal is all the way down. The little arm on the throttle spool is what closes the switch.

-- Joe

[PJ Grady Inc.]

Would I affect hot or cold idling chuggyness?41868
If the F. T. micro switch were stuck on it would provide an overly rich fuel ratio at idle which would cause a poor idle and "chugging" off the line.
Rob

[Jonathan]

^ what Joe said.

I'll also mention that if the little plunger that is hiding behind that metal flap is as dirty as the surrounding area, there is a good chance they might be stuck on.

When you floor the gas, the throttle spool rotates and pushes on the metal flap and in turn pushes in the little plunger on each switch. When you get off the gas, those plungers are supposed to pop back out. They won't if they are fouled up and dirty like that (or those screws on top got tightened too much and the switch got pinched).

You can very easily go without them, indefinitely by some suggestions, and all you do is unplug them. The connector is right up on top of the W pipe, just follow the wires. You can also swap them around if you find one works and one doesn't. You don't need to move the switch, just change which connector is going to the good one. Generally speaking, you want the kickdown switch to be the good one if you only have one to work with.

To answer your question for this or another thread, yes, these could both be causing you some of your problems. If they are stuck in and staying engaged the whole time, the transmission might be thinking it needs to stay in the lower gear longer. If the fuel enrichment switch is stuck engaged, your fuel mixture system could be giving the engine too much gas when it doesn't need it.

Like I said, unplug them now and rule it out, then circle back once you get the car running better.

The one referred to as having the flap is the one that all cars have, manuals and autos. This is why it gets mounted in the lower position and comes with the flap.

http://store.delorean.com/p-6650-microswitch-with-flap.aspx

The one without the flap is meant to be the kickdown switch for the auto trans and it gets mounted right on top of the other one, using the flap from the lower one.

http://store.delorean.com/p-8923-microswitch-without-flap.aspx

They are the same price and basically the same switch. You just need one with the flap and one without is all.

[Redsquall]

If the F. T. micro switch were stuck on it would provide an overly rich fuel ratio at idle which would cause a poor idle and "chugging" off the line.
Rob

I checked the WOT switches- both clearly click on and off when I push the flap no problem- Does that 100% mean they are good?

[Rich]

I checked the WOT switches- both clearly click on and off when I push the flap no problem- Does that 100% mean they are good?

It means they are being pushed on and off correctly, that the linkage and mechanical adjustments are OK when you manually override the accelerator pedal.

The real mechanical test is what happens when you push the accelerator pedal. Get a buddy to press the pedal to the floor (engine off) and check to see if both switches are activated (clicking as if they are switching). And, if activated, then check continuity of each pair of switch contacts if you have reason to think either of them might be bad inside. This second test is the electrical test. You can check it easily at the plug connectors for each switch.

[Jonathan]

Good point on mechanically working versus electrically.

It sounds like they probably work mechanically, assuming the check Rich mentioned with actually pushing the accelerator and seeing what the spool does to the switches is ok.

If there is a problem internally, electrical that is, unplugging them for the time being should allow you to move on with your issue resolving. It is conceivable too though that there could be an issue further back along that wiring. Not as likely as the switch having issues right at the switch.

You might want to have a look at the ECU and components in behind the driver's seat just for good measure. Things can go wonky in there too. Take photos if you'd like and post here. The box that typically is mounted vertical and has the long, single connector (that won't let you see the wires while installed) is the one which has the O2 sensor wires (among others) going to it. The other box lying on top of the bracket in that same space has wiring for some of the idle speed control components. I would probably look but not touch for right now in that area until you get other stuff sorted out.

[DMCMW Dave]

Good point on mechanically working versus electrically.

It sounds like they probably work mechanically, assuming the check Rich mentioned with actually pushing the accelerator and seeing what the spool does to the switches is ok.
.

Those switches are a pretty common failure. They can click and still be bad, but usually they just stick. If the one for the full throttle enrichment sticks closed (i.e. pushed) the dwell reading on the lambda system will never change as you make adjustments, i.e. it will read 55 all the time. If it sticks open you'll never notice it. If the transmission switch sticks closed the trans will shift at somewhat higher RPM than normal. If it sticks closed it won't downshift when you floor the throttle under some conditions.