1989 351w thermactor bypass valve normal state

[mikefamig]

I stiil might care though.. if the bypass or diverter are not working or not working well and it doesnt matter except passing emmissions.... ok thats one thing... but if its causing my engine exhaust to run hot on the passenger side I care because I have burned up spark plug wires several times over the last 15 years. Ultimately I want to find a definitive guide on removing all the thermacter stuff with engine in car. I dont have emmissions to worry about.

Burning plug wires is not an indication of the engine running too hot. You should read the coolant temperature and read the spark plugs.

 

[DWilliamA]

It's not a simple matter to remove the emission system because the computer unit is delivering fuel mix based on signals it receives from the system's sensors but I'm certain that it's been done countless times and you should be able to find what's necessary to make it run right on the net. It's a matter of stripping the system from of the engine and then dealing with the ECU to manage the EFI.

I have seen videos where the air pump has been bypassed successfully, I'm just not ambitious enough to pursue all this as long as the system is still working for me.

totally agree with your assessment ... my thing is everything appears to be working on my 90 5.8l but it continues to throw code 44 .. if it isn't working it certainly doesn't seem to matter much.. the truck is running better than it ever has before ..

 

[mikefamig]

totally agree with your assessment ... my thing is everything appears to be working on my 90 5.8l but it continues to throw code 44 .. if it isn't working it certainly doesn't seem to matter much.. the truck is running better than it ever has before ..

I recommend that you do what I did for my own. I traced the TAB and TAD circuits from end to end both electrical and vacuum circuits. You can test the solenoids with a 12vdc power source to see if they switch by putting a vacuum gauge on the line at the TAB.TAD valve and applying voltage to the solenoid. The vacuum should come and go as the solenoid opens and closes. Both TAD and TAB function the same. You may find a vacuum line leaking or a solenoid that isn't switching or whatever and even if you find nothing you will fully understand how it works by the time you are done.

Both solenoids are controlled by the computer. The TAB switches air from the AIR pump to either the TAD valve or the the fresh-air exhaust pipe. When the TAB is switched to send air to the TAD valve, the TAD valve switches that air to either the cylinder heads or to the cat converter. The wholething is a good excise in learning and understanding the system.

You pros out there please correct me if I'm wrong.

 

[L\Bronco]

I recommend that you do what I did for my own. I traced the TAB and TAD circuits from end to end both electrical and vacuum circuits. You can test the solenoids with a 12vdc power source to see if they switch by putting a vacuum gauge on the line at the TAB.TAD valve and applying voltage to the solenoid. The vacuum should come and go as the solenoid opens and closes. Both TAD and TAB function the same. You may find a vacuum line leaking or a solenoid that isn't switching or whatever and even if you find nothing you will fully understand how it works by the time you are done.

Both solenoids are controlled by the computer. The TAB switches air from the AIR pump to either the TAD valve or the the fresh-air exhaust pipe. When the TAB is switched to send air to the TAD valve, the TAD valve switches that air to either the cylinder heads or to the cat converter. The wholething is a good excise in learning and understanding the system.

You pros out there please correct me if I'm wrong.

That's right on the nose mikefamig
Fords THERMACTOR system, (Everyone else called it Air Injection Reaction (AIR)) was there to clean up post combustion HC & Co in the exhaust system when the engine and catalytic converter were cold, then feed oxygen to the cat for the reduction of HC & CO after the cat warmed up (or lit-off).
In short, the air would be sent upstream (into the heads before the cat) for warm up, then downstream to feed the cat without affecting the O2 sensor readings. This was done using the TAD solenoid (Thermactor Air Diverter)
On decel or extremely rich conditions the air would be dumped through a muffler to atmosphere to bypass the system to prevent backfiring. (TAB - Thermactor Air Bypass)
Hope that helps
Cheers

 

[L\Bronco]

totally agree with your assessment ... my thing is everything appears to be working on my 90 5.8l but it continues to throw code 44 .. if it isn't working it certainly doesn't seem to matter much.. the truck is running better than it ever has before ..

When the truck tests the thermactor system during KOER, it switches the pumped air between up stream of the O2 sensors (into the heads) and downstream (into the cat), then switches between upstream and dump or bypass. it looks for the O2 sensors to switch from rich to lean and back to rich.
As Motech said earlier, the onboard diagnostics for Thermactor was weak at best, so all you get is a system failure code which could be anything from a belt falling off to a pump failure, TAB or TAD sol or valve failures or even O2 sensor failures.
Make sure to run the truck at 1500 RPM for 2 min to get the O2 sensors hot and producing a good signal. Return to idle then run the KOER test without shutting it off. See if 44 is still there.
Back in the day a lean code 41 KOER from a failed sensor was almost always accompanied by a 44.

Plus, as I mentioned in my previous post, The system operates post combustion, It rarely affects engine operation unless Air goes upstream of the O2's when it shouldn't, then everything looks lean to the PCM.
A totally disabled system should have no affect on engine performance just emissions.
Hope that helps

 

[mikefamig]

When the truck tests the thermactor system during KOER, it switches the pumped air between up stream of the O2 sensors (into the heads) and downstream (into the cat), then switches between upstream and dump or bypass. it looks for the O2 sensors to switch from rich to lean and back to rich.
As Motech said earlier, the onboard diagnostics for Thermactor was weak at best, so all you get is a system failure code which could be anything from a belt falling off to a pump failure, TAB or TAD sol or valve failures or even O2 sensor failures.
Make sure to run the truck at 1500 RPM for 2 min to get the O2 sensors hot and producing a good signal. Return to idle then run the KOER test without shutting it off. See if 44 is still there.
Back in the day a lean code 41 KOER from a failed sensor was almost always accompanied by a 44.

Plus, as I mentioned in my previous post, The system operates post combustion, It rarely affects engine operation unless Air goes upstream of the O2's when it shouldn't, then everything looks lean to the PCM.
A totally disabled system should have no affect on engine performance just emissions.
Hope that helps

Good to know, thanks!

 

[Motech]

...my 90 5.8l but it continues to throw code 44 .. if it isn't working it certainly doesn't seem to matter much...

Now there's a sensible conclusion for sure.