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Discussion Starter · #1 ·
Last march I had code p1179. Also had a rattling in the cats, so I replaced the cats and O2 sensors. Starting a couple of months ago, I started getting the code again. I saved up and bought a new mass air flow sensor due to a recomondation I got, and that didn't fix it. Does anyone know what else I can try? Could one of the new 02 sensors gone bad, and if so, which one? I don't want to replace them all again. Any help would be appreciated. It's time to get it emissions tested, so got to figure it out.

Thanks,
Ryan
 

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Ryan,
I can't find the code info for that code.
Don't waste any more money till someone can tell you what has failed. Whar ever it is probably took out your cats and most likely will kill them again. Could be bad plug wires, injectors, any of a number of things that might cause rich exhaust and cat failure.
Mike J.
 

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Ok, I know this may sound strange but here goes:

P1179 - Maximum Negative AMFR Correction Fault

What is this telling you? P1179 means "long term fuel trim too rich, banks 1&2 (AMFR)." OK, so what does that mean? It means the O2(s) are telling the computer that it/they sense there is too much oxygen in the exhaust so the computer is attempting to compensate by telling the injectors to stay open longer each cycle so that the fuel/air mixture is correct; however, the computer has now reached the limits of the set parameters for the amount of fuel the factory believes your engine needs to run, hence "long term fuel trim too rich." Basically there is a window of too rich (P1179) and too lean (P1178). What causes this? Well several things and one of the worse things you can do is throw money at parts without taking the time to diagnose (you or your mechanic).

Here are a few items that can cause the computer to want to richen the fuel mixture:
O2(s) – dirty or bad
MAFS – dirty or bad
Low fuel pressure
Vacuum leak

In your shoes I would have checked my fuel pressure at the rail first. If the fuel pressure is too low then your injectors cannot squirt enough fuel into the cylinder during each cycle. The O2s sense this lean mixture by noting the higher than allowable level of oxygen in the exhaust and send the message to the computer. The computer tries to fix this by telling the fuel injectors to stay open longer, but eventually they can stay open only so long and your computer notes the fact that it can no longer match the level of fuel needed, so it logs P1179. If it does this two trips in a row it makes the little dash light turn on.

There is also the chance it could be a leak in the vacuum lines or a valve cover gasket for instance and the engine could actually be bringing in unreported air (air that the MAFS cannot account for).

You can get the same code from a bad O2 that sends the wrong information as well as a MAFS that tells the computer more air is coming into the engine than what really is.

With P1179 I would have checked fuel pressure and for a vacuum leak before moving to O2(s) or MAFS.

Go get a fuel pressure gauge for your tool box (less $ than taking it in and having it read by a mechanic) and let us know what it reads – should be in the 34psi to 36psi range. If this is good then start looking for a vacuum leak.

Hope this helps, Good luck, and report back.

-B
 

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Oh, have you gotten P1177, P1313, P1314 at any time during all this -or- had poorer (than normal) fuel ecomony -or- rough idle -or- hard starts from cold? I don't mean all of these or all the time, but any of them in addition to P1179

-B
 

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Discussion Starter · #5 ·
acornhoek said:
Oh, have you gotten P1177, P1313, P1314 at any time during all this -or- had poorer (than normal) fuel ecomony -or- rough idle -or- hard starts from cold? I don't mean all of these or all the time, but any of them in addition to P1179

-B
Actually, every once in a while it gives me some wacky code number, which the computer says is invalid. I rather think it's my code reader, by auto enginuity not reading it properly, in fact, it hasn't been saying what you said along with p1179, but it has been saying, "p1179 O2 Sensor Signal Circuit Slow Switching From Rich to Lean" but then again, it's been funny sometimes. Back in August when it went off, it did give me p1413, which it said was an invalid code, but could it have been 1314? What does that mean?

I have a fuel pressure gauge somewhere, I actually replaced the fuel pump and fuel filter in September, not because of this, but because it died on me, and the pressure tested good after that. I'll dig the gauge out and test it again. And thank you, every time I've had trouble with this, I haven't gotten a straight answer. I really appreciate it.

Thanks,
Ryan
 

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I got to hand it to you... acornhoek. That had to be the best answer for that code I have read yet.

A while back I was tripping P1178. I thought this was odd because for the first time in a long time, she was running better than ever. I changed out the plugs, replaced a cracked maniford, cleaned the contact on the MAS, replaced the plugs and wires, cleaned and decarboned the intake with a little Seafoam... not to mention added it to the gas a couple of tanks in a role. I have not had that code return since.

If it happens again, I will take the opposite of what you just said. LOL
 

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texasrover, P1178 would tell me the computer is trying to lean out the mixture to no avail, so I'd look at, Leaky Injectors, Poor spark - plugs/ wires, MAFS, O2s and some others. Fuel pressure could be too high as well, which would make me look at the fuel pressure regulator.

Sounds to me like you did the right things.......

-B
 

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Ryan, P1413 is not a Land Rover code (some one correct me if I'm wrong)......your computer wouldn't throw it. P1314 is Misfire Catalyst Damage Fault Bank B......the brother to P1313, which is Misfire Catalyst Damage Fault Bank A. One of these codes along with P1179, P1177 or both would make me suspect the fuel pressure......to start with. The lack of power in August was probably settled w/ the new fuel pump in September, but check the pressure again so you can rule it out.
 

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Discussion Starter · #10 ·
Yeah, that's the problem with my OBD2 reader. it is usually good, but once in a while gives me codes that are invalid. Don't know what to do with those, but it's always along with a good code when it happens. I couldn't find my pressure gauge tonight, so i'll pick one up tomorrow. Thanks again for the advice. It's really been helpful.

Ryan
 

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Fuel pressure looks good, as long as it didn't drop off when you turned off the key. You can then rule out the pump & filter and move on to vacuum.

Give a good check for a vacuum leak. Depending on what year your D1 is there should be a vacuum line diagram just in front of the radiator. Look for collapsed lines as well, and go ahead and clean your oil separator in the top of your right valve cover where the vacuum line attaches. There isn't one on the left side.

Oil separator? you ask. Pull the line from the top on the right valve cover (passenger's side) and you'll see the top of the piece in the picture below. Most of them are encrusted at this stage and can impede or block the correct flow through the vacuum lines.

Also check that you don't have a bad valve cover gasket. Oh, and don't forget to check the vacuum line to the fuel pressure regulator. The regulator can go bad and leak fuel back through the vacuum line into the plenum.

-B
 

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Oh yea, remove the oil separator to clean it......I've herd some suggesting spraying carb cleaner with the separator in place - this just sends the gunk down into the valve cover.
 

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Discussion Starter · #19 ·
Well, the check engine light came back on today. Unfortunately I painted the garage floor today, and have to wait at least 24 hours to be able to pull the rover in and test it. My lap top is down, so have an old PC in the garage to test it with. I'll update if it's the same code again.

Thanks,
Ryan
 

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Ryan- Any luck on p1179? Just wondering because I'm having the same problem. Sounds like you have done everything right so far.

acornhoek- What if you get a 38 psi reading on ignition turn on for 10 sec and then drops to 36. Pressure maintains at 30 while idling. If turned off and left for 30 min rail pressure drops to 25. Is that right?
 
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