Engine Code 94 and 13

[CmdrDerp]

Hey guys, first time poster...

Got myself a 1991 Mustang GT. I ran KOEO codes, and everything was fine. 11-10-11.

Ran KOER codes and got a 94 and 13.

Code 94: Thermactor Air System – Air Diverter (TAD) System Fault (Driver’s Side).
Code 13: Idle Speed Control – Cannot Control Idle at Engine RPM.

After doing a fair amount of research, I think code 94 indicates a blockage before the driver side heads from the TAD valve. It's typically accompanied by a code 44 (meaning the passenger side is blocked, too). Getting BOTH of these codes would be common, I think, if the smog pump or TAD valve wasn't working correctly. It means it's not pumping air to either of the heads.

The fact I'm NOT getting a code 44 might indicate an actual clog in the air crossover tube. I think the air goes from the smog pump, to the TAD valve, to the crossover tube, which first goes to the passenger side heads, then finally to the driver side heads. The fact that it seems to be going to the passenger side, but NOT the driver side would maybe indicate a clog in the Air Crossover Tube, right?

Btw, I live in California so removing this stuff (permanently) isn't an option for me.

My car has 70,000 original miles. Is it really possible that the Air Crossover Tube would be plugged up with so few miles?

So my questions: is this sound logic? Does this indicate my crossover tube must be clogged (with only 70k miles)? Or could this code 94 (and lack of 44) indicate something else?

And any thoughts on the code 13? Could this code be related to the 94?

I'm asking here first, because taking the Air Crossover Tube off is a PITA.

Thanks guys!

 

[AeroCoupe]

Code 13:

H

Thread 'KOER code 13'

Sep 17, 2010

I cant find any info on this code. all I know is it means Cannot control RPM during ER Self-Test low RPM check.

any info on this code.

this is the only code I get for KOEO and KOER
1992 5.0 LX

• Haus
• Replies: 21
• Forum: Fox 5.0 Mustang Tech

Codes 44 & 94:

Thread 'Code 94 And 44'

Oct 21, 2017

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??

• BlakeusMaximus
• Replies: 38
• Forum: Fox 5.0 Mustang Tech

It could be the hole in the head has carbon in it or the tube or both.

 

[CmdrDerp]

Thank you!

The Code 13 info you sent me is very interesting (tbh I haven't looked much into that issue yet). It sounds like Code 13 will trigger if my base idle is above 725, which it probably is. Although the idle is stable (no bursts or stalling), I can't really get it below 750-800 with the throttle stop screw, it closes the throttle plate completely at about 750. Also, when the car is warmed up, the base idle will sit around 900.

Would this indicate a vacuum leak? I've smoked tested it from the throttle body and I haven't seen any smoke leaking


Regarding the Code 94:

Could this be caused by a bad O2 sensor? I ended up ordering a couple. I think any problem before the crossover tube would cause a Code 44, too.

The only similar scenario I've seen is where this person was getting a Code 44 without a Code 94 (so the opposite of my problem, I guess):

S

Thread 'Code 44 without a code 94'

May 16, 2009

I have spent a couple of hours searching the forum on this and couldnt find a solution for this code on my 88 california 5.0



KOER test is giving me a code 44, Secondary air injection system inoperative (right side). Code 44 and 94 together usualy mean the Thermactor system isnt working properly, but a 44 on its own seems to mean the secondary air is being diverted just fine on the drivers side but not on the passenger side. My understanding is the thermactor air going to the back of the cylinder heads is not registering with the O2 sensor on the passenger side. I have tested the TAB...

• sln583
• Replies: 17
• Forum: Fox 5.0 Mustang Tech

 

[AeroCoupe]

Base idle reset may help and before you ask it's here (post #2):

Thread 'Help me create the "Surging Idle Checklist"'

Apr 10, 2005

Updated 05 July 2022 to add rough idle when cold and smooth idle when up to normal operating temperature. See the EGR tech information, section #15 for more help.

Many of you are familiar with the "Cranks OK, but No Start Checklist for Fuel Injected Mustangs" checklist and the No Crank Checklist. They are very effective in finding and eliminating the problems by use of a systematic process that checks and eliminates possible causes. This idle problem checklist will use the same troubleshooting strategy and methodology.

By the term surging idle, I mean an idle that...

• jrichker
• 1986 1993 86-93 check engine light code 67 cranks ok dump codes eec-iv mustang no start
• Replies: 575
• Forum: Fox 5.0 Mustang Tech

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