How did you get rid of EEC codes 44 and 94?

[st5150]

Hey guys, I had this topic going about a month ago. Someone here was nice enough to reply with a VERY detailed LONG write up. Unfortunately the server crashed and my post is gone. Someone else was on the thread with the same problem as I and we were sharing notes. Anyways, I'd like to track them down if possibe. With that said, here is my problem:

Stock 5.O. Only mods are an electric fan and cat back.

I'm getting EEC-IV error codes 44 and 94

Here is what I've replaced so far with no luck:

H pipe
O2 sensors
TAB valve
TAD valve
TAB solenoid
TAD solenoid

I have verified that the solenoids do open and there is vacuum present at both the TAB & TAD valves when their coresponding solenoids open.

There isn't much else to replace in the whole smog system:
The 1 way aluminum (flying saucer shaped) valves
The smog pump
Hoses carrying air from the smog pump




Can the 1 way valves go bad? The smog pump freely spins and I can hear it making a pumping noise (similar to an electric air compressor/pump), so I assume its working fine. I don't know what else to replace.

 

[HISSIN50]

not sure if the one way valves can go bad, but they are important (saves the pump in the event of a backfire, etc).

Jrichker was probably the one who replied with the long post - he is one of the SN wiseman and has great info. i might guess that he will see this in the morning and post for you.

good luck.

 

[jrichker]

Codes 94 & 44 - AIR system inoperative - Air Injection. Check vacuum lines for leaks, & cracks. 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 wheelwell 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 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. Starting the engine 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.

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. Power & ground supplied should turn on the vacuum flow, remove either one and the vacuum should stop flowing.
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

 

[st5150]

Thanks for the info guys.

I did some more wrenching today and here is what I found:


I disconnected the rubber hoses that pump smog to the cats and the heads. They disconnect where they connect to the aluminum pod shaped 1-way valves.

I ran the EEC-IV engine on test. Durring the test I verified that air from the smog pump properly gets diverted/fed to both 1 way valves just fine. This means that all my solenoids, valves, vacuum lines and hoses are working fine. This means if there is a problem with my smog pump air delivery system, its up-stream.

I also verified that my O2 sensors are grounded to the back of my heads.



I'd like more info on these one-way valves. What's their official name? What' s inside them? I think I sprayed some carb cleaner inside one of them. Think that'll harm it?

 

[jrichker]

The check valves prevent hot exhaust gases from flowing backward into the control valves at a time when the pressure on the control valve side is less than the exhaust pressure. This would be on full throttle acceleration, when the smog pump dumps it air output overboard and not through either the heads or cats.

The hot exhaust gases could easily damage the control valves due to heat and corrosion.

 

[st5150]

Thanks jrichker. Have you ever seen check valves go bad?


Since I verified that the check valves for both the cats and the heads are getting air from the smog pump when they're suppose to, from here on the only possible problems I see are:

A) the check valves not letting air through

or

B) My O2 sensors are weak (I've swapped out a couple of different used, but good condition O2 sensors and all of them made no notible change in fuel economy or fixed the 44 and 94 error codes) I also get ~255-275 miles a tank. Not bad.

or

C) carbon could have built up inside my heads and blocked the air ports (doubt it).

 

[jrichker]

Thanks jrichker. Have you ever seen check valves go bad?


Since I verified that the check valves for both the cats and the heads are getting air from the smog pump when they're suppose to, from here on the only possible problems I see are:

A) the check valves not letting air through

or

B) My O2 sensors are weak (I've swapped out a couple of different used, but good condition O2 sensors and all of them made no notible change in fuel economy or fixed the 44 and 94 error codes) I also get ~255-275 miles a tank. Not bad.

or

C) carbon could have built up inside my heads and blocked the air ports (doubt it).

A little bit of explanation may help insure we are talking about the same thing. The control valves have vacuum lines going to them and direct the smog pump output. They are connected by large rubber hoses on both ends.

The check valves are mounted on the air pipes, one for the pipe that bolts to the back of the heads (it screws on) and one for the pipe that goes to the cats (clamps on). They have large rubber hoses that go to the rear control valve.

If you do a Key On Engine On code test, the computer toggles all the actuators. You can use a test light across the actuator wiring to verify that the computer is signaling them to open & close. Just probe the actuator wiring from the rear of the connector. When the actuator toggles, the lamp will light, so listen and maybe you will hear them click.

 

[st5150]

Yes, we have our vocabulary aligned and are talking about the same thing.

I did almos the exact same test you suggested yesterday, except my test allowed me to verify that air generated from the smog pump was actually passing through the tubes:


I disconnected the hoses right before the check valves and stuck my fingers in them so I could feel the air flow. I then started the engine running EEC self test that cycled through the entire smog system and with my fingers I verified that the proper valves/solenoids were opening and closing as they should. The true test was feeling the air rush through the tubes. This means one of two things are my problem:

1) Air is reaching the check valves but not getting through.

2) My thermactor air ports in my heads are some how clogged and not letting air pass.


I can't imagine what else could be wrong, unless you have some more ideas?

Thanks for all your help.

 

[Zero_chance]

Did you try clearing the codes and seeing if they return?

 

[jrichker]

I have seen the pipe that connects the back of the heads fill with carbon. I had a piece of armored cable I put on the end of a drill and ran it through the pipe to remove the carbon.

With the engine off, you should be able to connect a piece of garden hose or heater hose to the check valves and blow through them by mouth with no trouble.

 

[st5150]

Zero_chance- The codes from the engine running test are not stored in the EEC.

jrichker- I installed a new check valve, the one that goes to the back of the heads (the only check valve that should trigger codes 94 and 44).... sure enough, the error code is still there!!! I tried blowing through my old valve, and yes it did not pass much air through it at all. I'm going to try and soak everything with carb cleaner, and shoot carb cleaner down the metal pipe on the back of the heads and see if it does anything. I am at a complete loss here because I've replaced every single sensor or valve in the system!


88 cent can of WALMART Carb cleaner here I come

 

[st5150]

have good news and bad news......


Good news: I passed smog! Flying colors: 14 HC at 15 mph, 8 HC at 25 mph. It was dead cats that were causing me to fail before.

Bad news: I still have codes 94 and 44. Fortunately they don't effect the smog numbers since air isn't pumped through the thermactor ports after the car has warmed up. Anyways, I'm fairly certain I found my problem: Either the metal tube in the back of the heads or the ports inside the heads are clogged up. I verified that my old check vavle was bad. Air would blow through it both ways. I'm suspicious this caused carbon to build up down stream in the system. I sprayed nearly a bottle of carb cleaner down the metal smog tube with no luck opening it up. I'm starting to not care anymore now that I'm passing smog so cleanly.

 

[jrichker]

I am glad you passed emissions testing.

Doing the Roto-Rooter thing to the smog tube that connects the heads worked for me. I had the engine out when I removed the tube. It would be harder to remove with the engine in the car, but still doable.

 

[SamSnyder]

I have had 94 and 44 for eight years now, and I just ignore them. I can't detect and effect on performance and have not had any problem passing California smog, since they don't read codes or test individual components. Maybe one day I'll get around to troubleshooting them, and then again, maybe not........

 

[st5150]

jrichker- Thanks for your help. Is the metal tubing that attaches to the back of the heads done so via a high temp gasket, or just high temp RTV? I haven't looked closely, but it looks like I can take it off with out removing (much of)anything. I already have a replacement tube that is 'clean'.

 

[jrichker]

It used a pair of gaskets, I don't remember much about them.