P1171 and P1174
 

I am having trouble with the dreaded lean codes in my son's 2003 disco. I need to get the car to pass emissions but can't due to the codes. I searched this quite a bit and get many threads on it but have not found a sound answer but quite a bit of speculation. A brief history, my son bought the car a little over 2 years ago with a bad engine. We replaced the engine ourselves with one we ordered off the internet. The engine, I was told, was from a 2004 with top hatted cylinders with around 70,000 miles. We put the engine in, drove around for a few hundred miles and it became emissions ready and passed. This was May 2013. In sometime during early 2014 the check engine light came on with codes P1171 and P1174. When it came time for emission, I replaced MAF (with a cheap one from autozone) and passed emissions but the light came on within a week or 2 of passing. My son has been driving the car around with the check engine light on most of this last year. I took the car to a local mechanic. He recommended a new MAF sensor as he thought the readings were erratic. I replaced with a new BOSCH maf sensor. He thought the readings looked better but still no help on the lean codes. I have my own scan tool and during this whole time, I have been watching the fuel trims to see what was going on. The short term fuel trim looks good most of the time. I do notice that when decelerating from a higher speed many times my STFT will peg at +25% on both banks. Once in a while at idle especially when i have not reached full operating temp, the STFT will creep up to around +20% or so. The mechanic duplicated the STFT increase while coasting down a hill, turned around and went down the same hill with the same results (+25% STFT). This is driving me crazy. I had the car smoked tested last year to find a leak in the intake side of the brake booster vacuum hose and the tiny hose next to it. I fixed both of those. Should I do another smoke test? Any suggestions? I am leaning toward a vacuum leak. Am I looking in the right direction?

I have the same issue (minus the top hat liners, sadly) and I do think you have a vacuum leak (and that I do as well). I had the codes before and they variously went away when I replaced upper intake gasket, the front vacuum fitting on the intake (I can't recall the name... the one with red keeper on the intake side), and the MAF.

For what it is worth, the codes stayed away a long time UNTIL I had to remove the upper intake to fix a leaking injector. I did not have a spare upper intake gasket at the time so I Re used mine. Also, the fuel rail is tight on the injectors. I haven't fixed it because I have a new engine coming very soon and I need all of the gaskets and o rings that come in the HG kit, but I strongly suspect the upper intake gasket and, to a lesser extent, the injector o rings.

I know MAF's are a hotly contested issue here but my amazon cheapie one has been working great for about a year.... I think!

But I am not a knowledgeable member... more knowledgeable ones will surely chime in.

Thanks for the reply, I too think the cheapie MAF was working just fine. I did fail to mention that the professional mechanic said that what was going on with the car did not make sense to him. As decelerating would be the least amount of fuel the car needs. He said that he had no smoke machine. He said in his 25 years of being a mechanic he never felt they were worth the cost. This mechanic was recommended to me by others and he did seem like he knew what he was doing, but did not want to "take on" the disco as he was not a "rover guy". He basically said "I don't want to waste your money or my time" at least he was honest.

At least you got a mechanic to talk to you! That problem is precisely why I am the dumb mechanic for my truck.

You can try a cigar smoke test. I found one major leak that way but it hasn't helped on the current one.

Have you checked the torque on your upper intake bolts (there are six)? I have found mine loose after a year of driving when I failed to loctite them. I tried to mash my gasket down a little... if that is the issue you might have better luck than I did.

I had the some problem for a while as well.
Checked all the usual suspects and could not find a vacuum leak anywhere.

I bit the bullet and bought a fuel injector o-ring and filter kit off eBay.
Took it all apart and did the fuel injector service and my lean code went away.
Unfortunately I got a bank 1 sensor 2 fault and found the O2 wire must have snagged the drive shaft. Luck would have it I had new after cat sensors I had never put on.
Let me tell you that sensor connector about the drive shaft it a bitch to get at!

Anyway all the codes have stayed away but I could smell fuel.
Took the plenum off today to find 3 of my new injector o-rings leaking at the fuel rail.
Pulled them back off and wiped them down, could see no damage so I put them back on.
Jumped the fuel pump relay this time to pressurize the fuel system and one was still leaking. Repeated the process again and it stopped leaking.
Must have had some crud in the fuel rail cups?
Still no codes and I don't smell and see fuel leaking all down the back of my motor!
Took about 4 hours to tear it all down, fix and reassemble not a bad day.

Steve

Well, I left out some of my problems... ALOT OF THEM... but I think part of it is that the fuel rail screws up the orings when you press it down.

You have a vac leak somewhere after the MAF. You are getting extra air in and it's causing lean codes. I've had these codes twice before. First time was the intake tube loose at the throttle body, the 2nd time was a bad fuel injector o-ring. I found both leaks using a home smoke test with a cigar.
You can also try and spray starting fluid around a few spots and see if the engine changes any, but I've never had much luck with that method unless you have a large leak.

The red clip Charlie is talking about is called the Brake servo hose and it's connected to the pass side of the intake. It's very common for that hose to brake if it's not taken off correctly.
Here is the Brake servo hose and red clip if you need them:
a)Hose - Brake Servo To Intake Manifold - Without Secondary Air Injection (Genuine Part # SQB103300 ) - Land Rover hoses from Atlantic British
b)Land Rover Intake Manifold Brake Servo Vacuum - Discovery II

And right under the brake servo connection mine has a plug that I have replaced a few time as they rot and start leaking.

These lean codes can drive you nuts sometimes. I've seen a lot of vehicles, not Rovers specifically, but many vehicles do this when the MAP sensor gives bad readings. (high fuel trim readings, especially during deceleration)
What does the O2 sensor data look like when the fuel trims go way positive like that? Are they dropping out completely? Or do they look like they are still working?
Just a thought... I just got these same two codes in my wife's car due to a bad fuel pump. You can get a cheap $20 fuel pressure gauge from Harbor Freight, if you don't have one already. I'm not sure that's your problem, but fuel delivery is probably the second thing I check after vacuum leaks when I get lean codes.
Also, have you tried replacing the fuel filter?

Sounds like you need the intake/o-rings refresh. Here is where I posted my process in this thread. No more CEL and passed smog without issues.

https://landroverforums.com/forum/di...e-73976/page3/

Generally a lean mix would indicate a leak in the intake side of the engine, or in some instances the exhaust side. You need to check all joints and gaskets on the intake side, including the injector seals, to ensure there's no unmetered air getting in. in the same way ensure there are no leaks in the exhaust side as once again this would dilute the exhaust gases before they reach the O2 sensors which would read the extra air as lean burn and signal the ECU to adapt the fuelling.

If you are sure there are no leaks, but the problem persists check all the injector electrical connections. Finally you may have to check the injectors are all working properly, as if any of them is not injecting the correct amount of fuel it would be read as a lean burn.

A friend of mine fought exactly those same codes for two years before he sold his truck. We tried smoke tests and everything else we could think of at the time. In the time since he sold his truck there have been several threads here about leaky injector O-rings being the source of this problem. My theory is that problems with injector O-rings are not revealed by typical smoke tests because smoke tests do not create as much pressure in the intake system as the vacuum generated by a running engine. If you've eliminated all other vac leak risks go ahead and replace the injector O-rings. I understand it's a more invasive task than some of the other fixes but it's not all that difficult. Just order the parts, including the upper intake manifold gasket, and spend a Saturday making your Rover all better.

I had my D2 for 7 years and fought a constant battle trying to sort out a lean mix problem. No matter what I did it simply seamed to evade me, until it dawned on me that while I had made doubly sure all the obvious seals and gaskets were sound I hadn't, nor had any mechanic, thought to look at the injector seals. So I set to and changed them. With the new ones in and everything back together, took it for a run and miracle of miracles it ran better than it ever had and a check with Nanocom Evo showed no more lean P codes.

It is important, when doing the injector seal, to clean the sockets in the manifold and the corresponding ones in the fuel rail and use an little engine oil to lubricate them so them slide in without being distorted. It only takes a small bit of dirt to undo all your hard work.

I'm following this thread too and that is real useful information. Thanks! When I have pressed my fuel rail down I've always been pretty sure I was screwing up the brand new seals because it was so difficult. Now I know why... no lubricant.

I want to ad that I just found this 11 page thread on fuel injectors. Really informative on cleaning and fixing them. Fuel Injector Thread

update: Just got home from my safety and emissions and it passed!! After the advice from the forum, I went and got an "official" smoke test from a mechanic. There was smoke coming out all over! There was quite a bit of smoke coming from under the upper and lower intake manifold (not sure what the upper one is called). With everything still attached to the car, it was very hard to tell exactly where it was coming from so I decided to replace all of them. Took the car apart all the way down to removing the valley gasket. Cleaned the surfaces up real good and started re-assembly. I noticed a few small scratches (not from me) on some of the sealing surfaces so I actually put permatex 1 minute gasket maker on both sides of all my gaskets (except the valve cover gaskets) to make sure the voids were filled in. Yes, I know the rave manual said to put the gaskets on dry, but I am so tired of these codes, I wanted to make sure it was sealed up. As I was putting it back together I did replace the injector o-rings. We have been driving the car around for maybe 75-100 miles to get it ready for the emissions test. Well I am happy to say that there are no pending or no codes and that I am at 7 ready and 1 not ready for the emissions test (you can pass emissions with 1 not ready). I know that is not much driving but I can tell you that before the work it would put p1171 and p1174 to pending within about 20 miles and the full blown codes would turn up not too long after that. The only thing that worries me, is that it still goes to +25 on the short term fuel trim on deceleration. But the difference is that is just bounces to +25 the immediately goes down to a normal range just around 0. The mechanic that looked at it the first time said that when it hits +25 two times it will turn on the lean code. It does not go to +25 every time but it has done it many times but no codes. Is it because it does not stay at +25 that is it not turning on the lean codes? Are my lean codes going to come back? Is it normal for a disco to hit +25 on deceleration? Am I safe (at least I passed emissions)? I did not re-do the smoke test to see how it was after the work. Should I do another smoke test?

Good to hear you fixed your problem. If I had to guess you had some bad injector o-rings.

What gaskets did the RAVE tell you to fit dry that you used RTV on? Please don't say the Upper intake gasket. I guess if there was a deep cut then you may of had no other choice. Although you will probably be okay if you used very little RTV, the upper intake gasket is a metal crush gasket and is designed to be sandwiched/crushed down into place between the two surfaces. I would imagine that if you had a lot of RTV on there it could get squeezed out into the air intake and possible work it's way to an intake valve. You are probably okay though if you used a small thin layer and left some room around the edge for it to expand.

Also, I used RTV on my valve cover gaskets and many others do also. It won't hurt anything if you use a nice thin layer and don't get gunk in your valves or anything. My valve covers haven't leaked a drop in over 50k miles :)