Code 94 And 44

BlakeusMaximus

Still got to try a little lube on my speedo head
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Jul 12, 2017
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So I scanned my 88GT today and came back with codes 94 and 44 with koer. I passed the koeo test with a code 11. I checked all hoses and appear to be good. Smog pump appears to be working. I’ve read that these codes don’t affect performance but it bugs me that their there. Some dudes say don’t worry about it, some say pull the tube off the back of the heads and clean it. What do you my fellow Mustang cronies think??
 
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Codes 44 & 94 - AIR system inoperative - Air Injection. Check vacuum lines for leaks, & cracks. Check for a clogged air crossover tube, where one or both sides of the tube clog with carbon.

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Revised 21 Sep 2012 to correct the description of the process that sets the code and include Thermactor Air System diagram.

If you have a catalytic converter H pipe, you need to fix these codes. If you don't, then don't worry about them.

Code 44 passenger side air not functioning.
Code 94 driver side air not functioning.

The TAD solenoid/TAD diverter valve directs smog pump output to either the crossover tube attached to the cylinder heads or to the catalytic converters.

The O2 sensors are placed before the catalytic converters, so they do not see the extra O2 when the smog pump's output is directed to the converters or the input just before the converter.

The 44/94 code uses the O2 sensors to detect a shift in the O2 level in the exhaust. The smog pump provides extra air to the exhaust which raises the O2 level in the exhaust when the smog pump output is directed through the crossover tube.

When there is an absence of increase in the O2 levels when the TAD solenoid/TAD diverter valve directs air through the crossover tube, it detects the lower O2 level and sets the code.

Failure mode is usually due to a clogged air crossover tube, where one or both sides of the tube clog with carbon. The air crossover tube mounts on the back of the cylinder heads and supplies air to each of the Thermactor air passages cast into the cylinder heads. When the heads do not get the proper air delivery, they set codes 44 & 94, depending on which passage is clogged. It is possible to get both 44 & 94, which would suggest that the air pump or control valves are not working correctly, or the crossover tube is full of carbon or missing.

Testing the system:
Note that the engine must be running to do the tests unless stated otherwise. For safety’s sake, do test preparation like loosening clamps, disconnecting hoses and connecting things to a vacuum source with the engine off.


Disconnect the big hose from smog pump: with the engine running you should feel air output. Reconnect the smog pump hose & apply vacuum to the first vacuum controlled valve: Its purpose is to either dump the pump's output to the atmosphere or pass it to the next valve.

The next vacuum controlled valve directs the air to either the cylinder heads when the engine is cold or to the catalytic converter when the engine is warm. Disconnect the big hoses from the back side of the vacuum controlled valve and start the engine. Apply vacuum to the valve and see if the airflow changes from one hose to the next.

The two electrical controlled vacuum valves mounted on the rear of the passenger side wheel well turn the vacuum on & off under computer control. Check to see that both valves have +12 volts on the red wire. Then ground the white/red wire and the first solenoid should open and pass vacuum. Do the same thing to the light green/black wire on the second solenoid and it should open and pass vacuum.

Remember that the computer does not source power for any actuator or relay, but provides the ground necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side will go to ground or below 1 volt as the computer switches on that circuit.

The following computer tests are done with the engine not running.
The computer provides the ground to complete the circuit to power the solenoid valve that turns the
vacuum on or off. The computer is located under the passenger side kick panel. Remove the kick panel & the cover over the computer wiring connector pins. Check Pin 38 Solenoid valve #1 that provides vacuum to the first Thermactor control valve for a switch from 12-14 volts to 1 volt or less. Do the same with pin 32 solenoid valve #2 that provides vacuum to the second Thermactor control valve. Turning the ignition to Run with the computer jumpered to self-test mode will cause all the actuators to toggle on and off. If after doing this and you see no switching of the voltage on and off, you can start testing the wiring for shorts to ground and broken wiring. An Ohm check to ground with the computer connector disconnected & the solenoid valves disconnected should show open circuit between the pin 32 and ground and again on pin 38 and ground. In like manner, there should be less than 1 ohm between pin 32 and solenoid valve #2 and pin 38 & Solenoid valve #1.

The following computer tests are done with the engine running.
If after checking the resistance of the wiring & you are sure that there are no wiring faults, start looking at the solenoid valves. If you disconnect them, you can jumper power & ground to them to verify operation with the engine running. Power & ground supplied should turn on the vacuum flow, remove either one and the vacuum should stop flowing.

Typical resistance of the solenoid valves is in the range of 20-70 Ohms.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif

If you have a catalytic converter H pipe, you need to fix these codes. If you don't, then don't worry about them
 

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Put it this way...I have a code 44 I'm pretty sure is due to that tube and am in no hurry to pull it off. It can be done though, but the blockage could also be in the head.
 
So I can drive the car this way and still pass emissions and not cause any drivability issues? I do have a explorer upper and lower intake im going to put on at some point. I’ll probably just worry about it then if it’s not going to cause me any issues.
 
Only if the issue lies in the yellow portion as indicated above. If the blockage or break is in the orange portion, you won't pass and you'll need to troubleshoot that. Could be a solenoid not opening.

Basically the yellow portion is only active during warmup. Once the car is warmed up, the air flows straight from pump to cats. If you g do your testing when car fully warmed, the yellow portion never comes into play.

if you have an actual sniffer test, is probably pull the tube off and clear it out. It can be removed, just tricky to reach.

I have no sniff test, so that's why I don't care
 
I bought the car in February and the previous owner told me it didn’t pass before he sold it to me. I replaced the 02 sensors, act sensor, coolant temp sensor, spark plugs, wires, cap and rotor, coil, egr valve, pvc valve. I think that’s it. It passed with flying colors in March and the cars runs better than any other foxbody I’ve owned, I’ve had 3 of them. I’m guessing those codes have been stored in the computer for a long time.
 
Computer rest? Disconnect battery and leave it sit for a while? Maybe replace the those solenoids while it’s disconnected? If it’s the smog tube that’s clogged, I guess I’ll just worry about it when I replace my intake with the gt40 I picked up.
 
I’m bringing up the intake swap because it’ll be easier to get access to the smog tube with it out of the way. Tab and tad solenoids aren’t that expensive to replace so I’m thinking about just throwing new ones in. I’m not having any drivability issues and I passed emissions just fine, just bugging me that I have codes is all.
 
I’m bringing up the intake swap because it’ll be easier to get access to the smog tube with it out of the way. Tab and tad solenoids aren’t that expensive to replace so I’m thinking about just throwing new ones in. I’m not having any drivability issues and I passed emissions just fine, just bugging me that I have codes is all.
Don't throw parts, time and money at the problem in hope of solving it. All that will do is to make your wallet feel pain and make you more frustrated.

You have the complete diagnostic and test routines laid out for you, so get with it and find the problem.
 
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You guys have told me pretty much what the problem is and I appreciate it. I don’t want you guys to think I’m one to just throw parts at issues with my car. I don’t mind pulling the tube and cleaning it out, all I’m saying is it’ll probably be easier to do it when I swap the intake out, (easier access). The solenoids are 30 years old, I would feel better knowing they are new for restoration purposes. I guess, what I’m asking, based off your guys experience, that freaking tube is clogged right? And is it something I can wait on??
 
Car isn't going to run any differently. It's really just a smog issue.

Reset your ECU and run the codes again. If they are still there, I'd probably pull the tube and clean them. Make sure you have a good mirror to look inside th me port where the heads are to see if they are clogged in there.

As for making sure the solenoids are working, pop the rubber hose off the tube and start the car cold. You should feel Air pulsing out. If not, the two solenoids betwwwn smog pump and the head tube could be junk
 
Here some more diagrams to help you out

IMG_3954.GIF


You need to see if the diverted and bypass valve are receiving vacuum and actually sending air from the pump to the heads. Those vac lines frequently breaks

IMG_3955.JPG


Smog pump hooks up on hose end to left. Metal tube runs to h pipe, open hose and at right connects to tube on back of heads