Progress Thread 1993 Ford Mustang 5.0 convertible stock manual - ODB Codes shows running lean

mcalvo · Feb 11, 2025

Gentlemen;

Once again I need your expertise. I pulled codes on my 5.0 I have the list below.

KOEO
67 - Park/Neutral Position (PNP) switch circuit open – A/C on during Self-Test
10 -
11 - System PASS

KOER
40 -
41 - HO2S circuit indicates system lean (right HO2S)
91 - HO2S circuit Indicates system loan (left HO2S)
** I recently changed the o2 sensors and still have the above error codes. I also clean the MAF sensor as well

Cylinder Balance Test
30 - Cylinder 3 is not cooperating to engine performance. Not working
** I am wondering if just changing the cable would fix this. I just don't want to get into fuel injectors.

Got description from https://obdadvisor.com/codes/ford-obd1-codes/

Once again, thank you very much for your input. I greatly appreciate it. I need the car to pass emissions. It has not failed yet but I would like to have the highest chance of passing.

Thanks
-Max

Noobz347 · Feb 11, 2025

You need a [Progress Thread]. Let's make it this thread.

So, start with year/make/model and mods along with any recent maintenance you've done or issues that you've resolved.

Progress Thread Tip - You can always edit the thread title to reflect the current issue.

Having everything that's going on with the car helps quite a bit as you go through the car.

Next: We're probably going to ask questions about your fuel system.

gkomo · Feb 11, 2025

How do you do a cylinder balance test? Or is that part of the KOER testing?

General karthief · Feb 11, 2025

gkomo said:
How do you do a cylinder balance test? Or is that part of the KOER testing?

Happens during the KOER test
@mcalvo
Surprised is did the cyl balance test with the 67 code
Anyway the lean codes do not reflect a bad 02 sensor, the dead #3 cylinder is the most likely culprit, pull the plug, if it smells like fuel you have a dead plug or wire, likely it will be clean and dry, I suspect the #3 injector, a node light will be used to check if the signal is being sent then the injector is not injecting, if they are original then i'd pull all and get them rebuilt (flow tested).
Just the musings of a backyard fiddler of automotive junk, not necessarily a trained tech like a lot of other members here but I try hard to fit in

AeroCoupe · Feb 11, 2025

Was the motor up to operating temperature prior to the KOER test?

gkomo · Feb 11, 2025

How did you get to do KOER when you had KOEO code 67? I thought it wouldn’t do it unless all KOEO codes were cleared?

Mustang5L5 · Feb 12, 2025

gkomo said:
How did you get to do KOER when you had KOEO code 67? I thought it wouldn’t do it unless all KOEO codes were cleared?

Sometimes it will go. I've been able to dump codes with a code 67. A good way around this is to press the clutch in during the test. Code 67 is linked to the plug on top of the T5 (NGS) and one of the plugs on the clutch switch. 9 times out of 10 it's the plug on top of the T5 not being connected because they are using a 4-cyl or SN95 T5 that doesn't have the plug and/or someone told them it is not needed. If pressing the clutch in causes the code 67 to go away, the issue is that plug.

gkomo said:
How do you do a cylinder balance test? Or is that part of the KOER testing?

Towards the end of this video. It goes through all the trsts, plus the wiggle test plus the CBT

View: https://youtu.be/Hwtm6avQMPc?si=WeLIwaOpbseCiygd

Mustang5L5 · Feb 12, 2025

mcalvo said:
KOEO
67 - Park/Neutral Position (PNP) switch circuit open – A/C on during Self-Test
10 -
11 - System PASS

KOER
40 -
41 - HO2S circuit indicates system lean (right HO2S)
91 - HO2S circuit Indicates system loan (left HO2S)
** I recently changed the o2 sensors and still have the above error codes. I also clean the MAF sensor as well

Cylinder Balance Test
30 - Cylinder 3 is not cooperating to engine performance. Not working
** I am wondering if just changing the cable would fix this. I just don't want to get into fuel injectors.

Next time you run the test, try it with the clutch pedal depressed. If code 67 goes away, it's likely an issue with the wiring to the sensor on top of the T5.

As for the remaining codes, i would troubleshoot cylinder 3 first. Try swapping the plug, wire and injector to another cylinder and rerun and see if it moves. That way you can ID the issue before firing the parts cannon off. If that fails and cyl 3 is still an issue, do a compression test.

I wouldn't worry about code 41/91 for now, as they could be a cause of the misfiring cylinder. Granted I would expect to see only one side lean but right now the major issue you have is a non-contributing cylinder.

gkomo · Feb 12, 2025

Mustang5L5 said:
Sometimes it will go. I've been able to dump codes with a code 67. A good way around this is to press the clutch in during the test. Code 67 is linked to the plug on top of the T5 (NGS) and one of the plugs on the clutch switch. 9 times out of 10 it's the plug on top of the T5 not being connected because they are using a 4-cyl or SN95 T5 that doesn't have the plug and/or someone told them it is not needed. If pressing the clutch in causes the code 67 to go away, the issue is that plug.

Towards the end of this video. It goes through all the trsts, plus the wiggle test plus the CBT

View: https://youtu.be/Hwtm6avQMPc?si=WeLIwaOpbseCiygd

Good to know. I currently to have KOEO code 67 and bought a new sensor that you’re referring to. Just haven’t had time to install it and rerun my KOEO test.

I’ll also have to try pressing in the clutch to run KOER tests as I haven’t done that yet if I can’t get to the sensor first or that ends up not being my issue.

mcalvo · Feb 13, 2025

AeroCoupe said:
Was the motor up to operating temperature prior to the KOER test?

Yes Sir, I drove the car for10 minutes and let it idle for another 10 minutes. Is that not enough??

mcalvo · Feb 13, 2025

gkomo said:
How did you get to do KOER when you had KOEO code 67? I thought it wouldn’t do it unless all KOEO codes were cleared?

Code 67 is just the parking switch

AeroCoupe · Feb 13, 2025

I would think so being you are in Phoenix it should have gotten up to temp.

mcalvo · Feb 19, 2025

Noobz347 said:
You need a [Progress Thread]. Let's make it this thread.

So, start with year/make/model and mods along with any recent maintenance you've done or issues that you've resolved.

Progress Thread Tip - You can always edit the thread title to reflect the current issue.

Having everything that's going on with the car helps quite a bit as you go through the car.

Next: We're probably going to ask questions about your fuel system.

Howdy there;
I have changed the title for this thread. I have created other threads in the past. Should I link them to this thread as a progress that I have already done?

mcalvo · Feb 19, 2025

Mustang5L5 said:
Sometimes it will go. I've been able to dump codes with a code 67. A good way around this is to press the clutch in during the test. Code 67 is linked to the plug on top of the T5 (NGS) and one of the plugs on the clutch switch. 9 times out of 10 it's the plug on top of the T5 not being connected because they are using a 4-cyl or SN95 T5 that doesn't have the plug and/or someone told them it is not needed. If pressing the clutch in causes the code 67 to go away, the issue is that plug.

Towards the end of this video. It goes through all the trsts, plus the wiggle test plus the CBT

View: https://youtu.be/Hwtm6avQMPc?si=WeLIwaOpbseCiygd

Mike;

Thank you for the info. I watched your video. Very informative. I also subscribed to your channel. I will be updating this thread in the next couple of days.

Noobz347 · Feb 19, 2025

mcalvo said:
Howdy there;
I have changed the title for this thread. I have created other threads in the past. Should I link them to this thread as a progress that I have already done?

I would recommend doing that as you think it becomes relevant. Say, you already have an electrical issue someplace, solved or unsolved, and you're currently tackling some other electrical system issue.

That said... It might not be a bad idea to edit your first post to include an index of your other threads. I saw somebody else do that in here and I think it worked out great.

You can also post a link to this thread in your others and close them (get mod assistance with this part if you don't have the perms). Just let folks know you have a [Progress Thread] going.

I usually recommend these kinds of thread to folks that look like they be around a while. It will save you a lot of time particularly, when these old heads start becoming familiar with your progress.

General karthief · Feb 20, 2025

Noobz347 said:
when these old heads

Really??
Old Heads???
I resemble that remark!!

mcalvo · Feb 21, 2025

General karthief said:
Really??
Old Heads???
I resemble that remark!!

I am pretty sure he meant to say "these *experienced* heads".

Noobz347 · Feb 21, 2025

mcalvo said:
I am pretty sure he meant to say "these *experienced* heads".

He's from Florida. If you pander to them they can smell your fear.

mcalvo · Feb 21, 2025

Howdy there folks;

Here is an update to this post from last week. As suggested to swapped the wire I dis so for cylinders 2 & 3 at the spark plug and distributor cap as well.
AND IT WORKED!!!
The amount of power was awesome!! It sure feels like a V8. The second reason I bought the car. The first is of course, it's a fox body.

I pulled codes after a trip to the car wash, Denny's and Costco in that order. I got pics below to show you folks.

KOEO

There is a code 10 but pic was not good

KOER

I am still running lean and once again I am asking for your suggestions.

A big thanks to "General karthief" for his suggestion of swapping the wire. It certainly that was the fix.

General karthief · Feb 22, 2025

Did you clear the codes before the drive ?
Lean on both sensors may be low fuel pressure or a vacuum leak.
Or both.

Progress Thread 1993 Ford Mustang 5.0 convertible stock manual - ODB Codes shows running lean

Member

Stangnet Facilities Maint Tech... Er... Janitor

now i can hopefully expect to receive the shaft

wonder how much it would cost to ship you a pair

lube between the nut and the face. I know my lubes

now i can hopefully expect to receive the shaft

That is…until I whipped out my Bissell

That is…until I whipped out my Bissell

now i can hopefully expect to receive the shaft

Member

Member

lube between the nut and the face. I know my lubes

Member

Member

Stangnet Facilities Maint Tech... Er... Janitor

wonder how much it would cost to ship you a pair

Member

Stangnet Facilities Maint Tech... Er... Janitor

Member

wonder how much it would cost to ship you a pair

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