Okay before I had codes 1171, 1174 so I repalced both upstream O2's with brand new Bosch ones and spray cleaned the MAF, then cleared codes and now 2 days later 0174, 1171, 1174 popped back up, what the H E double hockey sticks is wrong. What else will cause these codes maybe a vacume leak. Yes I run 91 octane all the time incase anyone ask's. Please help I just finally glued my hair back on from the last issue I had.

 

from what I understand a smoke test is in order otherwise you will continue to throw parts at the problem....

 

Cleaning the MAF is a big debate topic around these parts, find someone with a working MAF and see if it fixes your problem or bite the bullet and buy a new one (cheapest I found was BP Utah $135+shipping).

 

See attached page from ECU manual. The 1170 series of codes refer to adaptive values being out of range. Imagine that the balance of air, temp, fuel temp, throttle position are all the edges of a piece of plywood, balanced on a bowling ball. One side dips, the other is adjusted, etc. Computer has limits, you are exceeding them. When you clear codes, it will come back in two driving cycles (cold engine start).

So it was not fixed by what you did two days ago. Never do the happy dance until a week or two has gone by.

One of the things the computer tries to compensate for is air that sneaks in beyond the MAF sensor, this is called un-metered air. Can be a vac leak, a crack in a air hose corrugated fold, etc. One pro LR tech talked about using a clean oil filter and stuffing it into the intake air hose to make the vac leak really whistle loud.

I have no problem cleaning an MAF with made for the job MAF spray, done when vehicle has sat overnight, and ignition switch has not been turned on even to listen to the radio. When the main relay fires up, it will apply power to the MAF, which heats an internal spot very hot as part of the air flow detection. On a D1, that is like 350F above ambient. A D2 is somewhat different, but the concept is the same; spray can propellant cools rapidly upon exit of the can, and what you are spraying is real hot, and can be big $$$ (D1 MAF $1400) or hard to get. I have sprayed my D1 and several Mercedes (Bosch) MAFs.

 

Are you using a stock airfilter or a KN? The oil used to prep those filters can foul up the MAFs if you use too much. What brand 02 sensors did you use?

 

Go buy some cheap cigars and do a smoke test or take it to a mechanic and have them smoke test it. I had these codes and it turned out the be a worn out intake tube that wasn't sealing right on the throttle body. Air was getting in past the MAF so it was give the lean codes you are getting.

Other people that had these codes also had vacuume leaks. One had a worn injector o-ring and another had a bad valve cover gasket that was sucking in air and so on.....

It seems that a lot of people put new O2 sensors or MAF trying to solve this, but were still getting the codes. In fact I have yet to find a thread where someone has fixed these codes and found the problem to be something other then a Vacuum leak.


To do the cigar smoke test:

1) remove the top piece that covers the air filter
2) use a latex glove and stretch it over the opening in the intake tube to create an air tight seal for the smoke test.
3) remove the hose next to the brake servo on the intake manifold and connect another hose (about 3ft long) to the intake that you will blow some smoke into.
4) plug the old hose you disconnected from the intake manifold with something.
5) Light up a cigar and blow it into the hose you connected to the intake and watch for smoke leaking out.
6) Plug the hose you are blowing smoke into with your finger or bend it on the every time you blow in smoke to keep the smoke from escaping.

Note: You will need to blow a few puffs of smoke into the engine and then bend the hose or plug it with your finger before you will start to see it come out. You will be able to tell if you have a good seal because the latex glove on the intake will inflate like a balloon. If you blow to much in there then the glove will fly off so watch it.

 

Have you done any work where the transmission or transfer case was taken out and put back in? The reason I ask is because if the rear O2 sensor connectors get swapped side to side, you will get those codes. What you end up with is the r/r sensor trying to monitor the l/f sensor (and the other way too) getting all confused so it generates a code. I've only seen this a couple of times over the years, pretty unusual because it normally only happens after the transfer has been taken out and the connectors get mixed up side to side.

 

Well I did notice on the bell housing one of the big rubber plugs that are on either side is missing not sure if that will cause anything. Well I decided to do the carb cleaner trick to find a vavuum leak before I spend the money on a smoke test. I found that on the passenger side when I sprayed down between the Plenum were there was an opening that it bogged down. Now since its hard to see anything there its, either a injector O'ring, Plenum gasket or a Intake gasket. judging by how low i sprayed probably a O'ring or intake gasket. So I thought it over and I came up with the reasoning eventually my head gasket is going to go as all discovery gaskets go so to jump ahead of the game I'm just go to order a compleete head gasket kit and install everything. It will be my second head gasket kit I have down on a land rover as this time will be a breese for me. I did a gasket kit on the other rover I owned then sold it and I have never heard of any problems from my work yet. So just finding time to do it now. If I leave this issue for a while will it cause any other harm besides to my wallet cause of the extra gas I will be burning.