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2006-2009 Range Rover MkIII / L322
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Discussion Starter #1
I've been having ongoing problems for the last 2 years that I still haven't solved. Currently I'm trying to figure out why I'm getting lean codes on 1 and 2 banks. At idle the LTFT is 18 and STFT is 0. At 2500 RPM LT drops to 10.2 on the 7.6 while STFT stays at 0. Last week when I checked the STFT was jumping all over the place but it didn't when I looked today. Based on the fact that LTFT drops at raised RPMs it leads me to believe there is a vacuum leak. Would any of you agree or disagree with that? I tried using carb cleaner to find a leak with no success. I also made a homemade smoke tester but no smoke was detected. I swear I can hear a hiss on the drivers side of the engine but can't pin point it. Any ideas? Thank you, Rob 2006 RR HSE 145k
 

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2002-2005 Range Rover MkIII / L322
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Has the intake manifold ever been off? If not, then the intake seals may be leaking after 145k miles.
 

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Discussion Starter #3
Any idea why cold weather would make my problem go away? Anytime it's dipped to a fairly cold temp my codes have gone away. I'm not getting a vacuum leak until it heats back up outside.
 

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Discussion Starter #5
Yes, I actually just had it off last month but didn't replace the gasket(or seals). I ordered them from my dealership, should already be there but haven't had time to go get them.
 

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Well when you do an incomplete repair without installing gaskets, what would you expect? Revisit this thread when you have properly completed what ever you were doing with the intake and have gaskets installed and torqued.
 

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Discussion Starter #7
Will do. I actually hadn't planned on taking the intake off while I was doing my plugs and valve gaskets. When I did I just wanted to get it back together because I had a coolant leak and wanted to make sure it was fixed. I knew I could go back and take care of the intake because it's an easy fix.
 

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These intake seals get hard and brittle as they age. If you haven't had to replace them by 100k miles, then any work you do around them tends to break their seal.

My guess as to why cold weather doesn't trigger it is that the engine remains open loop mixture until it fully warms up. You may not be driving it long enough to get to closed loop and trigger the code.
 

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Discussion Starter #9
CJD, I just realized you and I may be talking about two different things. I ordered the metal gaskets for the intake. Since it's metal and you're saying brittle are we talking about the same thing? Excuse me for not knowing all of the parts but I did replace the seal in front of the intake because the part in front of it was leaking coolant. It had a gasket or seal that I did replace.
 

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I think you're talking about the throttle body. If you replaced that with an old gasket, then that is a prime suspect. But above I was referring to the actual manifold that covers the center top of the engine valley. The throttle body also connects to the front of it.
 

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Discussion Starter #11
I replaced the gasket in between the manifold and throttle body. The only gaskets on the manifold outside of that oring are the two metal ones. Are those the ones you're talking about? Or am I missing some others?
 

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Discussion Starter #13

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Discussion Starter #14
Also, if I went and had a smoke test run on it I should be able to see if those seals are leaking?
 

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Yes...the Jag engine has more than one intake seal. Numbers 9,10,12,and 14 are all possible sources of intake leaks. I am assuming you have already checked all the hoses connected to the manifold...as I think you said you did in the initial post. Because you are getting lean code on both banks, that tells you it is something in the general vicinity of the main intake manifold...in other words, a leak in gasket 10 would likely only affect a single cylinder. Gaskets 9,12 and 14 will affect both banks.

A smoke test could show the leak, but if it is up under the intake manifold it may be difficult to tell. It's still a good idea to try it, to prevent having to take the manifold off.

Air leaks are a pain. It is a game of ruling out each possible source until you find the one causing the problem.
 

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Discussion Starter #16
I guess I'll be going to get the smoke test this week. Every gasket connected to the intake has been changed but I'm still getting the lean codes on both banks.
 

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i had lean codes and via smoke test discovered the o ring in the vac tube to the power brake booster was leaking at the back of the intake manifold.
took less than 5 min for the smoke to start escaping

im a believer now
 

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Bummer. Still, at your car's mileage it was worth the time to change those gaskets. They should now be good for the life of the car. At this point a smoke test is your best bet.

Just a thought...another "low tech" way to look for leaks is to use a 1/4-3/8" hose and put one end to your ear. Use the other end to search for possible leaks around the engine compartment. Like a stethoscope...you are looking for hissing noises.

One other item we have not discussed is the Mass flow sensor (MAF). If it is dirty or bad and reading low, it can generate lean codes.
 

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Discussion Starter #19
CJD, what should the MAF be reading? You said if it's reading low so I'm guessing it has a normal range.

I actually have a car stethoscope but I can't pinpoint any hissing noises. I wanted to take it to get smoke tested this weekend but ended up being busy the whole time and couldn't. I'm going to try one day this week.
 

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I'm not really sure of the actual reading for the MAF. It's a simple little mechanism...a heated coil that gets cooled by the incoming air. By measuring the rate it cools the computer deduces the airflow through the throttle body. If it gets dirty over time, then the dirt acts like an insulator and makes the computer think the airflow is less than the actual air flow.

I didn't think about the MAF earlier, as normally when it starts to go bad the engine has some running problems to go along with it.

Just groping for possibilities...cracks or loose connections in the exhaust between the engine and O2 sensors can also let air in that causes the sensors to read lean when the mixture is actually normal or even rich from the computer compensating for the reading. My RR is an '04, and it got lean codes on first the left, caused by a crack in the pipe to the 1st catalytic converter. It was covered under an extended warranty from LR. The next year I got a lean code right...for the same reason. Still under warranty, but I got on the dealer for not covering both sides at the first incidence.

The exhaust cracks would normally only affect one side, unless both sides are actually cracked or leaking at the manifold seal. You can most easily detect exhaust leaks by starting the engine cold and immediately feeling for exhaust blowing an inch or so away from the pipes and joints...in the minute is takes for the pipes to get really hot!

The final cause I can think of is a crack in the intake manifold. This is not common at all, but possible if it was over-torqued.

Anyway...sorry you haven't found the issue yet. We are down to the less common possibilities.
 
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