Hi Guys, I'm hoping someone has had the same issue I'm having with my Rover and has solved the puzzle. 2006 LR3 4.4L with 120,000 miles

My check engine light came on last year with codes p0171 & p0174 (lean bank 1 & lean bank 2). I noticed the PCV valve was making a loud vacuum noise and if you remove the oil fill cap the engine is sucking air like crazy. To the point it wants to stall if the cap is removed. I replaced the PCV, it still had a slight vacuum noise but the light went off. A couple months later it comes back on and the PCV is bad again (it is sucking oil through the valve). I've replaced the PCV again but I'm sure it wont last long cause there seems to be excessive vacuum from the intake and the light is not going away this time.

I took it to my local Land Rover guys and they cant solve the riddle. So far we have replaced the MAF sensor, smoke tested for vacuum leaks and found none, tested this newest PCV, ran a 3 stage clean through the intake and fuel system. Im still getting the lean codes and excessive vacuum.

Another thing that may be worth mentioning. The oil dipstick was missing for a while before the light came on and I replaced it afterwards. I understand that unmetered air was likely entering the PCV system when this was off. Maybe something was permanently damaged?

Does anybody have an idea what could be causing this? The shop says that the fuel trims are normal.

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When the light comes back on, do the same fuel trim codes come back? I ask, because you said the fuel trims are normal. Also, what does the shop consider normal? Can you post the STFT & LTFT for both banks?

What brand MAF sensor did you use? Only one brand has been proven to work. I have had "off" brands not work, right out of the box.

Do you reset the fuel adaptations each time you do a repair? Even if you "fix" the problem, you will continue to set codes until the computer relearns the changes unless you reset them yourself.

Lastly, you may have one of the few trucks that have not had the software update for P0171 & P0174 yet. Might be worth looking into.

P.S. the PCV valves has always been loud on these and removing the oil cap will change the pitch, since it is a "closed" system. If you are using a factory vent valve, I'd say you are fine. If in doubt, get a vacuum gauge that reads in inches/H20 or millibar and we can compare specs.

 

My truck will stall if the oil fill cap is removed while it is idling. I thought that was normal?

 

LR Techniker, Thanks for the reply!

The shop told me the fuel trims were staying around 0 when they were monitoring them. I just checked the "freeze frame data" with my cheap code reader. This freeze frame data is suppose to show conditions at the time that the light came on. Here is where the fuel trims were when the light tripped.

Loan 59%
RPM 1475
STFT -1.6
LTFT 9.4
STFT -2.3
LTFT 7.8

We used a MAF sensor from the Dealer (Delphi I think). It didn't solve the problem so they took it off and put the original back on. The original is definitely a Delphi sensor.

How do I reset the fuel adaptations? This sounds like a logical solution since the car was sucking air through the dipstick tube for a while it may need to be reset.

Software Update: I've read about this on the forum. I do not have a scan tool that can do this. Is there any way to do find out if I need the update? The closest dealer is a bit of a drive so I would likely need to take a day off work in order to have them look at it. Is there any other way to tell?

I hope you're right about the PCV system. Hopefully this newest PCV valve will hold up and not allow the system to pull oil from the crankcase like the last. Thanks for all the help!!!

 

The fuel trims that you posted are borderline. Ideally, you want your trims +/- 5%. 10% is allowable, but usually indicates there is an issue on the horizon. Faults don't usually set until you get over 10%.

I question the MAF, because they have a high failure rate and I keep them in stock as a result. My fear is that you may have "fixed" the issue with the MAF, but because you didn't reset the fuel trims, they light may have erroneously reset.

To reset the fuel trims, you need a bi-directional scantool that has a feature to reset them. Unfortunately, a code reader won't do it.

To know if you have the latest software, requires hooking it up to the computer. We don't know if a car is current or not, until we hook up to program it, and right before we program, the computer will tell us if we are current or not. Not a very good method, but its how Land Rover does it.

 

LR Techniker

Ok, I'm going to order a new Delphi MAF Sensor from Rock Auto and install it myself. If I disconnect both battery cables and connect them with a jumper wire for about 30 minutes will that reset the adaptation codes? I've read about this hard reset on the forums but cannot tell for sure if it will reset the adaptations in this case. Thanks Again!

 

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Here is an example of checking software. I just looked at a 2012 RRS to see if it had current Transmission Software before I started digging deeper. As you can see, it is current as of today, so no programming needed. Had there been an update, I would have clicked on one button and it would have started. What a waste of time.

Anyway, I can't guarantee that your MAF is faulty, but we do see lots of them fail and cause those lean codes. I noticed you said "DELPHI", that isn't the OE supplier, DENSO is. There IS a difference! Get a DENSO.

As for adaptations, in theory, the battery reset might do it, but it is hard to say for sure.

Of course, if you really don't have the newest software, hanging parts on the car won't solve the issue. Its rare though, most have been done by now.

 

I did the hard reset (removed cables and used a jump wire) and it must have reset the adaptations cause the Rover was driving like a new car! The light came back on after about 25 miles and I think it is starting to feel sluggish off the line again.

I will replace the MAF (Denso) and reset adaptations again and then update this post so everyone can see the result. Thanks!

 

I tried for weeks to solve this issue and paid the local LR specialist about $500 to track it down with no luck! I replaced the MAF sensor like I mentioned above, did a " hard reset" and the light was back on after 25 miles. The car was running like crap as well. I was ready to take it to the Dealer convinced that I either was not getting the adaptations reset or I needed the PCM update. I decided to disconnect the battery overnight and let the system drain hoping thatbwould reset adaptations. I'm happy to report that it worked. Finally! I've got 100 miles on it since with no CEL and its running great! Thanks LRTechniker!

 

After spending about $500 with my local LR shop and not getting anywhere I've finally gotten rid of the CEL and got the Rover running great again. Thanks LRTechniker!

It must have been the fuel trim adaptations and my "Hard Rest" was not resetting them. As a last effort before taking it to the Dealer I disconnected the negative battery cable overnight and let the system drain completely. I'm now over 200 miles with no CEL and no more sluggish issues!