Code 179 explanation please.
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New User
Joined: May 2003
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From: Louisiana
Code 179 explanation please.
'94 F-150 300 ci 6 cyl. EFI
I have pulled code 179 - Fuel system at part throttle rich adaptive limit, system lean (Rear Side).
This is after having trouble with the engine starting after reaching normal temperature and finding the code that led me to replace the ECT sensor. This cured that problem and led to better performance and warm starts without problems. No more black smoke and better gas mileage also.
I am just learning about EFI and wonder if someone could explain the meaning of the above mentioned code, especially the "Rear Side" portion. I would like to know where to begin the next troubleshooting exploration of solving this code.
Thanks in advance.
I have pulled code 179 - Fuel system at part throttle rich adaptive limit, system lean (Rear Side).
This is after having trouble with the engine starting after reaching normal temperature and finding the code that led me to replace the ECT sensor. This cured that problem and led to better performance and warm starts without problems. No more black smoke and better gas mileage also.
I am just learning about EFI and wonder if someone could explain the meaning of the above mentioned code, especially the "Rear Side" portion. I would like to know where to begin the next troubleshooting exploration of solving this code.
Thanks in advance.
Hotshot
Joined: Aug 2002
Posts: 12,679
Likes: 15
From: BC, Canada
Code 179 explanation please.
Hi 94156 and welcome to FTE 
The 179 code means the engine is running too rich and the PCM has leaned it out as much as possible but it's still too rich.
The code is for the Right or Rear 02 sensor if it has more than 1 sensor.
A fairly common problem that causes that code is the fuel pressure is too high due to a bad regulator. I think that having the fuel pressure checked would be a good place to start.
After that you could have a MAP problem. A vacuum leak can cause the MAP to not read correctly. A very common place for a vacuum leak on a 300 is the throttle body gasket where it bolts onto the intake manifold. I would pick up a new gasket and then take the throttle body off and have a look. They are usually sucked in.
Let us know what you find.
The 179 code means the engine is running too rich and the PCM has leaned it out as much as possible but it's still too rich.
The code is for the Right or Rear 02 sensor if it has more than 1 sensor.
A fairly common problem that causes that code is the fuel pressure is too high due to a bad regulator. I think that having the fuel pressure checked would be a good place to start.
After that you could have a MAP problem. A vacuum leak can cause the MAP to not read correctly. A very common place for a vacuum leak on a 300 is the throttle body gasket where it bolts onto the intake manifold. I would pick up a new gasket and then take the throttle body off and have a look. They are usually sucked in.
Let us know what you find.
Last edited by Racerguy; May 18, 2003 at 12:41 PM.
Hotshot
Joined: Oct 2002
Posts: 18,488
Likes: 22
From: The Big, Oregon
Code 179 explanation please.
Racerguy- I think you have it backwards. It has reached the rich limit, the system is running lean. This is usually what happens after fixing a smoking problem. While smoking, the O2s gets coated with carbon, and can no longer read the actual oxy level in the exhaust, so the computer reads the lack of a signal as a lean mix. Just replace the O2s, and you should be good to go.
Hotshot
Joined: Aug 2002
Posts: 12,679
Likes: 15
From: BC, Canada
Code 179 explanation please.
Ford_Six do you wanna fight about it?
lol
I hope I'm not confused here
The rich limit, running lean and vice versa thing can get confusing.
Here is what the shop manual says.....
179 Right or Rear Lean limit reached.
182 Right or Rear Lean limit reached
at idle.
188 Left or Front Lean limit reached.
191 Left or Front Lean limit reached
at idle.
These DTCs indicate that the system is running rich, although strategy adjusted it to Max. lean.
You are right that it could be a simple O2 problem though but I like to check the other things first before throwing parts at it
lol
I hope I'm not confused here
The rich limit, running lean and vice versa thing can get confusing.
Here is what the shop manual says.....
179 Right or Rear Lean limit reached.
182 Right or Rear Lean limit reached
at idle.
188 Left or Front Lean limit reached.
191 Left or Front Lean limit reached
at idle.
These DTCs indicate that the system is running rich, although strategy adjusted it to Max. lean.
You are right that it could be a simple O2 problem though but I like to check the other things first before throwing parts at it
Last edited by Racerguy; May 18, 2003 at 01:56 PM.
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New User
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From: Louisiana
Code 179 explanation please.
I just happened to have an O2 sensor in the drawer from a failed attempt to clear a CEL when the truck was only a couple of years old and was still there after replacing the O2 sensor. I kept the one he took out.
The one I replaced was absolutely covered with carbon.
I thought initially that the problem was solved but after a few miles the 179 returned.
I'm looking for a fuel pressure guage to check the regulator. If I have to buy one I might just go ahead and buy the regulator.
If I buy a guage and the regulator is bad I'll have to buy the regulator also. If the regulator is good I have bought a guage that I probably will never use again.
I haven't had time to look at it again yet but I will let you know which way I go and what happens.
The old CEL problem when the truck was new is a real story for another time when I have time to write it all out.
The one I replaced was absolutely covered with carbon.
I thought initially that the problem was solved but after a few miles the 179 returned.
I'm looking for a fuel pressure guage to check the regulator. If I have to buy one I might just go ahead and buy the regulator.
If I buy a guage and the regulator is bad I'll have to buy the regulator also. If the regulator is good I have bought a guage that I probably will never use again.
I haven't had time to look at it again yet but I will let you know which way I go and what happens.
The old CEL problem when the truck was new is a real story for another time when I have time to write it all out.
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