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/