What is a thermactor and how do I fix it?

Funanin · Apr 24, 2005

I am pulling a code 44 and 94 which is thermactor malfunction and solenoid circuit failure. Im pretty sure they are tied together because they both came about at the same time so if I fix one I think they both will dissappear. So what is a thermactor, where is it and how do I fix it? Any help appreciated.

vikingpower · Apr 24, 2005

Check the air pump and the air junction valves that the air pump pushes air through to the cats and the exhaust port air injection in the heads. try running an air line directly from the air pump to the cats and plug off the line that leads to the heads. But, you didnt say of your car was OBD I or II so it may not work...

southbronx · Apr 24, 2005

The two are known as TAB/TAD solenoid (Thermactor Air Bypass/Thermactor Air Diverter). They sit on the passenger side wheel well with vacuum lines going to the bypass/divert valves on your smog system.

44 (r): Thermactor air injection system inoperative, bank #1. Suspect AIR pump, diverter valve, solenoids, harness.
94 (r): Thermactor air injection system inoperative, bank #2. Suspect AIR pump, diverter valve, solenoids, harness.

Check your air pump, hoses, lines and check valves for leaks or breakage. Repair/replace whats broken.

Carefully disconnect the vacuum lines from the valves (on the hose) and see if the valves hold vacuum, if not replace. If they do, disconnect the vacuum lines from the solenoids, hook up a vacuum pump to the top port and do a KOEO test. At the end of the test the TAB/TAD solenoids will cycle on/off when you move the throttle plate (you'll hear them click). Apply some vacuum. Your test light should come on/off when you move the throttle plate and the vacuum gauge should bleed off. If you don't hear them cycle on/off, check for ground at the connector(s). The puter only provides the ground as a switch. If you have good ground and the vacuum still holds then the solenoid(s) are bad-->replace. If you can't get the vacuum to hold on either solenoid, check for vacuum leaks on the plastic vacuum lines or at the black connector.

Here's a diagram:
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg
Here's another good link:
http://www.corral.net/forums/showthread.php?t=92388&highlight=TAB/TAD

Funanin · Apr 24, 2005

my car is a 93 LX, so obviously i am OBD-I, but also I dont have any smog equipment. I took it all off. Thing is, I wasnt throwing these codes until now. I had 2 bad O2 sensors and just replaced them, then checked to make sure the codes were gone for those (41 & 91), which they were, but then these 2 showed up. Was the computer somehow not seeing the 44 and 94 because the 41 and 91 were more important codes and now that the 41 and 91 are fixed it is showing me whats next in line of importance to be fixed?

haze187 · Apr 24, 2005

is your check engine light off? I took all my smog stuff out also and my check engine light it also off, I think I did pull those codes, but Im pretty sure they do not effect anything

southbronx · Apr 24, 2005

Sorry, didn't read your sig. :damnit: You'll have to place a 10 kOhm resistor on the feed back wire to simulate the load. Here's the tech article for a guy with a 92.

http://www.ffcobra.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=33;t=018802

Hope this helps...

haze187 · Apr 24, 2005

southbronx said:
Sorry, didn't read your sig. :damnit: You'll have to place a 10 kOhm resistor on the feed back wire to simulate the load. Here's the tech article for a guy with a 92.

http://www.ffcobra.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=33;t=018802

Hope this helps...

That is brilliant!

Funanin · Apr 25, 2005

so all that does is simulate a vacuum load so the sensor turns the check engine light off? If thats all that it does, then I need not do it because the bulb on my check engine light is burned out. haha, I had bad O2's and like 5 other codes for years and never knew it till I got a code reader from walmart!

haze187 · Apr 25, 2005

Funanin said:
so all that does is simulate a vacuum load so the sensor turns the check engine light off? If thats all that it does, then I need not do it because the bulb on my check engine light is burned out. haha, I had bad O2's and like 5 other codes for years and never knew it till I got a code reader from walmart!

no dude, this is not just cosmetic, when that light is on, your computer is going to be messign with the fuel and timing and such, which is going to effect the performance, you want to put that dummy sensor on, its inexpensive, you will get a code 33 which means its stuck closed, which is what you want, it wont throw the light on, but it will always be there. you DO NOT want your check engine light on because of EGR!

Funanin · Apr 26, 2005

dude what are you talking about EGR has nothing to do with this.

haze187 · Apr 26, 2005

Funanin said:
dude what are you talking about EGR has nothing to do with this.

I was thinking you were talking about that thread link, they were talking about EGR, and that is the only thing that will make the light go on, and make your car run like crap, none of the other things will make your light go on, just throug codes that are harmless....

southbronx · Apr 26, 2005

There's an indirect connection on how the EGR affects the check engine light.

The check engine light will come on if the computer cannot resolve the parameters in a given situation when it seems the reading from the O2 sensors are off. Hence, if you have a clogged thermactor system or check valves, the air that would normally be diverted down stream to lean out the excess gas mixture in the exhaust would be pumped back into the engine. The O2 sensors may get fouled (hence the light) and the increased fuel vapors sucked back in the block may find it's way into the EGR (the air would carry more soot) and cause the build-up on the diaphram/valve stem causing the PFE (the sensor attached to the EGR valve) to get a false reading. The combination of these "failures" would normally be captured with the 44/94 codes, but always check the sub-systems to be sure. Most mechs default to check engine light = O2 sensors, which may or may not be true. The heat would normally burn off the residue, but over a period of time, it will eventually get fouled. Any codes for the EGR (and sub-systems) should be inspected carefully. My thoughts...

jrichker · Apr 26, 2005

southbronx said:
There's an indirect connection on how the EGR affects the check engine light.

The check engine light will come on if the computer cannot resolve the parameters in a given situation when it seems the reading from the O2 sensors are off.

Hence, if you have a clogged thermactor system or check valves, the air that would normally be diverted down stream to lean out the excess gas mixture in the exhaust would be pumped back into the engine.

The O2 sensors may get fouled (hence the light) and the increased fuel vapors sucked back in the block may find it's way into the EGR (the air would carry more soot) and cause the build-up on the diaphram/valve stem causing the PFE (the sensor attached to the EGR valve) to get a false reading.

The combination of these "failures" would normally be captured with the 44/94 codes, but always check the sub-systems to be sure. Most mechs default to check engine light = O2 sensors, which may or may not be true. The heat would normally burn off the residue, but over a period of time, it will eventually get fouled. Any codes for the EGR (and sub-systems) should be inspected carefully. My thoughts...

Close, but still some problems with how it works.

The Thermactor air supplies extra oxygen to the cat converters to promote the catalytic reaction that converts the unburned Hydrocarbons into water vapor & CO2.

"The O2 sensors may get fouled (hence the light) and the increased fuel vapors sucked back in the block may find it's way into the EGR (the air would carry more soot) and cause the build-up on the diaphram/valve stem causing the PFE (the sensor attached to the EGR valve) to get a false reading." This would trip a 34 code,- EGR voltage above closed limit - Failed sensor, carbon between EGR pintle valve and seat holding the valve off its seat.

Pur Pony · May 26, 2005

if removing the egr, smog pump, and thermactors.... cant you just turn all of these off with an aftermarket chip, tuner, tweecer, etc?

I just removed my smog pump and egr. I bought the plug in for the egr to tell the computer that its still there and put the resister in the egr solenoid... I still have a check engine light but have not pulled the codes yet. My car is running like total crap now. I do have a tweecer and am going to turn the egr and the thermactors off and just remove them totally.

haze187 · May 26, 2005

pull codes before you remove them from your computer, let us know

DanMcD90 · Jan 23, 2008

im confused

I dont know too much about all this stuff, but my car is shaking like crazy, and it goes up and down with the RPMs. It doesnt happen all the time, but most of the time it does, i also wanna put in a new exhaust system, but i dont know if i can plug the hose that would normally go to the cat...can i? and why is it shaking?

bloopbloob · Jan 23, 2008

welcome, but you could start with a new thread!
and a better description is needed than that if/when you do make one

matt427 · Aug 2, 2010

Codes 94, 44, 34

I am getting those codes (94,44,34) Haven't checked anything physically yet. But car is hesitating, spitting, and sputtering especially when you first fire it up in the morning. It doesn't have the power it used to. It's like even if you get through the spitting and sputtering, it is down on power from 2000 rpm and above. That was usually where these cars made their power. It also has a problem of reving and not wanting to fall when you shift. It's almost like the throttle gets stuck around 2000 rpm. I have read that the IAC could cause this problem, but i'm not so sure. Not getting any codes that point to that. BTW, 1987 Mustang GT, 5-speed....bone stock. Speed Density I have read and read forums. Just trying to actually get to talk to someone that can shed some light on the subject for me personally. Any help is greatly appreciated!

jonkiny · Feb 24, 2019

I tried the 10K ohm resistors on both thermactors. The car ran OK but would not restart until I removed one of the resistors. The engine light still came on like always, when speeding up or slowing down. I then took the thermactors to the work bench and checked the resistance on both of them. It was 79 to 80 Ohms on both of them. 10K does not come close to the right resistance. I then applied vacuum to each of the ports on the thermactors and there was no change in the resistance. I'mcan try 80 ohm resistors but I can just leave the thermactors hooked up instead.
This setup is for a 91 to 93 Mustang 5.0 HO that I put in my 73 mustang.

Mustang5L5 · Feb 24, 2019

What's the code? The thernsctor codes don't set the check engine light off. They log in the memory to tell the ECU the system is disabled but don't affect how the car runs.

Pretty much anyone who has ditched the smog pump has those codes but they don't trigger the CEL.

What code numbers do you have?

What is a thermactor and how do I fix it?

Funanin

vikingpower

New Member

southbronx

New Member

Funanin

haze187

southbronx

New Member

haze187

Funanin

haze187

Funanin

haze187

southbronx

New Member

jrichker

StangNet's favorite TOOL

Pur Pony

haze187

DanMcD90

New Member

bloopbloob

Member

matt427

New Member

jonkiny

New Member

Mustang5L5

That is…until I whipped out my Bissell

Similar threads

What is a thermactor and how do I fix it?

New Member

New Member

New Member

New Member

StangNet's favorite TOOL

New Member

Member

New Member

New Member

That is…until I whipped out my Bissell

Similar threads

Privacy & Transparency

Privacy & Transparency