Hot Idle Compensator Issues

[rellison1]

Hello everyone,
I am having an issue with my 1984 5.0 with a Holly 4180c. After some research and a lot of troubleshooting I think I have narrowed the issue I'm having to be coming from the "Hot Idle Compensator" or at least thats what i have researched that people have been calling it online. The issue i am having is poor idle and continuous backfire when this is plugged in. As soon as I unplug it but leave the fast idle solenoid connected to the carburetor, the car will run great and there will be no backfire and it will idle normal. I have tried just running the car with it unplugged but as soon as I unplug it and drive it a little bit, the battery dies. I do not have air conditioning in the car so the fast idle solenoid has never been plugged in. I have no idea how this is causing the problems it is and there is little information about it on the web. If someone could help me identify why this problem is occurring that would be greatly appreciated. Thank you!

[rellison1]

[attach]107391

[rellison1]

Not sure if that is for sure what it is called, the switch I am having the issues with is the one that is located under the fast idle solenoid. It is somewhat shown in this picture and has the two wires coming out of it and into the plug.

[JacksAO]

Not sure if that is for sure what it is called, the switch I am having the issues with is the one that is located under the fast idle solenoid. It is somewhat shown in this picture and has the two wires coming out of it and into the plug.

I believe that's the W O T (wide open throttle cut out switch) and on my 85 5.0 GT it cuts out the AC compressor at wide open throttle.

[mrriggs]

It sounds like you need to get a schematic for your car and start tracing wires. Something may be shorted out or hooked up wrong. Maybe someone wired the alternator through the switch thinking that it would free up some horsepower at WOT [not considering that the ignition output drops when the alternator isn't working].

[jessesandy]

Are you unplugging the single wire that goes to the electric choke on the passenger side ?

[rellison1]

No, I am not

[rellison1]

I believe that's the W O T (wide open throttle cut out switch) and on my 85 5.0 GT it cuts out the AC compressor at wide open throttle.

Hmmm... That makes sense, guess I've never heard of one, but you can definitely see where the throttle linkage on the carburetor contacts the switch at full throttle. But considering the fact that I don't have a compressor in my car and it didn't come with one from the factory I wonder why it would be killing my battery when I unplug it...

[rellison1]

It sounds like you need to get a schematic for your car and start tracing wires. Something may be shorted out or hooked up wrong. Maybe someone wired the alternator through the switch thinking that it would free up some horsepower at WOT [not considering that the ignition output drops when the alternator isn't working].

I'm assuming that a short or wiring issue is definitely an issue considering the fact that I don't have Air Conditioning, I'm just confused that I never had the issue and then one day it just started giving me problems. It took a lot of troubleshooting but i finally tracked it down to this switch. I even tried taping the switch closed to imitate a wide open throttle scenario and while my car ran great, it still ended up killing my battery after a little driving. I also don't understand why it is causing my engine to backfire and run crappy when the switch is open (not contacted.)

[jessesandy]

At the very least, that switch controls the canister purge solenoids and the dump solenoid for the thermactor dump valve.
(I didn't verify if it is also used to shut off A/C at WOT)(But you don't have A/C anyway ?) (And I'm not saying this is all it controls)

The WOT switch is a normally closed switch. When the throttle is wide open and "presses" the switch, the electrical contacts are open.

When the ignition is on, the canister purge solenoids (normally open to air/vapor flow) activate and block the hoses from carb bowls to charcoal canisters. At WOT, the switch deactivates the canister purge solenoids.

At WOT, the switch activates the dump solenoid which cuts vacuum to the thermactor dump valve which causes smog pump air to vent to the atmosphere.

As far as killing the battery... ?!?
Is it charging ?
What happens, the car stops running ? As all ready mentioned, is battery voltage too low for ignition system to work ?

Also, the WOT switch is fuse protected (if, for example the insulation flakes off the wires and short to the motor) (ask me how I know )

[rellison1]

At the very least, that switch controls the canister purge solenoids and the dump solenoid for the thermactor dump valve.
(I didn't verify if it is also used to shut off A/C at WOT)(But you don't have A/C anyway ?) (And I'm not saying this is all it controls)

The WOT switch is a normally closed switch. When the throttle is wide open and "presses" the switch, the electrical contacts are open.

When the ignition is on, the canister purge solenoids (normally open to air/vapor flow) activate and block the hoses from carb bowls to charcoal canisters. At WOT, the switch deactivates the canister purge solenoids.

At WOT, the switch activates the dump solenoid which cuts vacuum to the thermactor dump valve which causes smog pump air to vent to the atmosphere.

As far as killing the battery... ?!?
Is it charging ?
What happens, the car stops running ? As all ready mentioned, is battery voltage too low for ignition system to work ?

Also, the WOT switch is fuse protected (if, for example the insulation flakes off the wires and short to the motor) (ask me how I know )

Wow! I had no idea it did all that. Do you think there is a chance that one of the canister purge solenoids or the dump solenoid is not working properly, causing the car to backfire on downshifts and whenever i let off the gas? This is actually the first time I have ever heard about either of the solenoids, Im may have seen them at some point but there is a lot of emissions parts on this motor and I'm slowly trying to understand it all and piece it all together.

As far as the battery charging, I have a brand new battery, alternator and voltage regulator (all got replaced trying to solve this issue) and they all work perfectly fine as long as the WOT switch is not activated. As soon as it is activated or unplugged (which I have tried several times) the car will run fine but after about 30mins to an hour of driving, my radio will quit working, gauges will quit working and lights will start to dim but the car will continue to run alright. As soon as i shut the car off, the battery is so dead that it won't even turn the engine over once. Its like it puts out enough power to run the ignition system and that is it.

With the WOT switch being fuse protected, do you think there could perhaps be a blown fuse causing some of my issues?

[mrriggs]

Do you think there is a chance that one of the canister purge solenoids or the dump solenoid is not working properly, causing the car to backfire on downshifts and whenever i let off the gas?

Ah ha! You mentioned the backfire before but the part about it happening every time you let off the gas is key. That is a thermactor issue. The dump valve is not dumping when the throttle is closed.

I didn't know the throttle switch engaged the dump valve but that explains why it's not backfiring when the switch is unplugged. If everything else works as it should when the switch is plugged in then you may not have any electrical troubles, just a thermactor issue.

[jessesandy]

^^The WOT switch at the carb causes dump at wide open throttle. This is another thread that talks about the WOT switch.
http://vb.foureyedpride.com/showthre...mbly-huh/page2

I'd connect a volt meter to the battery and see if it is charging ( +13.8v ) all the time when the failure happens.

Check all the battery cables and ground.

[jessesandy]

I found another thread that says the Canister Purge solenoids are not controlled by the WOT switch on '84 and '85 models.
Only '83 models (which I have) do this. (And this was wrong from Ford ?)

http://vb.foureyedpride.com/showthre...ght=WOT+switch

I'm going to ask the experts in the emissions forum.

[Walking-Tall]

Sounds like a whole buncha convoluted reasons to disconnect it all.

[jessesandy]

Here is another thread that hopefully explains the battery going dead.
It's a Ford Service Bulletin for 1984 Mustang/Capri showing the WOT switch is used to cut alternator output at WOT to free up a few horsepower.

http://vb.foureyedpride.com/showthre...ght=WOT+switch

The WOT switch needs to be connected (or the two wires jumpered together) for the alternator to work.

[rellison1]

Ah ha! You mentioned the backfire before but the part about it happening every time you let off the gas is key. That is a thermactor issue. The dump valve is not dumping when the throttle is closed.

I didn't know the throttle switch engaged the dump valve but that explains why it's not backfiring when the switch is unplugged. If everything else works as it should when the switch is plugged in then you may not have any electrical troubles, just a thermactor issue.

That seems very plausible, I guess I'm not real familier with the thermactor dump valve. Where is this located and what exactly does it do?

[rellison1]

Here is another thread that hopefully explains the battery going dead.
It's a Ford Service Bulletin for 1984 Mustang/Capri showing the WOT switch is used to cut alternator output at WOT to free up a few horsepower.

http://vb.foureyedpride.com/showthre...ght=WOT+switch

The WOT switch needs to be connected (or the two wires jumpered together) for the alternator to work.

That is pretty crazy! Never would have guessed but it makes perfect sense as to why my battery was dying when the WOT switch was contacted or unplugged. Basically i was tricking the car into thinking it was at WOT and therefore it was cutting the alternator output to free up some horsepower. Now i guess i got that part figured out, now I just need to figure out why it is backfiring and running funny.

[rellison1]

Sounds like a whole buncha convoluted reasons to disconnect it all.

I hear ya! I would like to maybe someday but for now I would like to drive it and have everything work right. I guess its a good way for me to learn how everything works until i can save up the money to delete everything.

[rellison1]

Sounds like a whole buncha convoluted reasons to disconnect it all.

I hear ya! I would like to maybe someday but for now I would like to drive it and have everything work right. I guess its a good way for me to learn how everything works until i can save up the money to delete everything.

[rellison1]

Is there any chance that this is the thermactor dump valve? If not, does anyone happen to know what this part is?

[rellison1]

[jessesandy]

That's a thermactor diverter valve.
It takes the air from the smog pump and directs it to the exhaust stream at the heads or down to the catalytic converter(s).

Follow the air hose out of the smog pump and the bypass valve should be first, then the diverter valve, then check valves.

The check valves prevent exhaust from flowing back to the thermactor valves.
A failed/ stuck open check valve could be your "continuous backfire" problem.

[JACook]

The thermactor dump (aka bypass) valve is on the back of the air pump, and is controlled by manifold vacuum.
When there's no manifold vacuum, the valve should dump air from the pump to atmosphere. This is why the air
injection system does nothing at WOT.

The diverter valve pictured above is controlled by EGR vacuum, and in 5-speed cars, defaults to upstream air.
This is done by installing the valve with the vacuum nipple pointed toward the front of the car. (ECU-controlled
models install the valve with the vacuum nipple pointed up, which provides downstream air by default.)

Typically backfire is a symptom of a bypass problem, especially if the delay valve is not in place in the line to the
valve. But if your diverter valve is not functioning, your exhaust will be running way hotter than it should, which
can also cause backfire problems. Has your EGR system been... altered at all?

[rellison1]

The thermactor dump (aka bypass) valve is on the back of the air pump, and is controlled by manifold vacuum.
When there's no manifold vacuum, the valve should dump air from the pump to atmosphere. This is why the air
injection system does nothing at WOT.

The diverter valve pictured above is controlled by EGR vacuum, and in 5-speed cars, defaults to upstream air.
This is done by installing the valve with the vacuum nipple pointed toward the front of the car. (ECU-controlled
models install the valve with the vacuum nipple pointed up, which provides downstream air by default.)

Typically backfire is a symptom of a bypass problem, especially if the delay valve is not in place in the line to the
valve. But if your diverter valve is not functioning, your exhaust will be running way hotter than it should, which
can also cause backfire problems. Has your EGR system been... altered at all?

No, The EGR system has been untouched. I cleaned the system up and replaced old cracking vacuum lines from it but that is all.