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Discussion Starter · #1 ·
I've got a head scratcher..

Two years ago, I had an issue with my thermostat housing cracking internally. About 4-5 months after I replaced that, I would get random "Reduced Engine Performance" messages on the screen, usually when going down a big hill on the highway, and it would clear before I got off the highway. Code reader (IIDTool) would see nothing. It would come and go, and eventually, I moved and stopped driving so many highway miles and it didn't really come back.


Fast forward to this January, I was driving home from work when the check engine light came on. Using my tool, I saw that it was a P0171-00 "System too lean (bank 1)". I opened the hood and looked around, but didn't see anything amiss, reset the code and went in and researched (I sometimes get random suspension codes too, so didn't know if this was real or not, as I have been fighting water infiltration on the passenger side for a while).

The next morning, a Friday, as I was dropping my kids off at school, the truck stalled in the drop off line. I turned the key back to start, without turning it to off, and it restarted right away, but idle was rough, and stalled two more times. The last time was as I was dropping the kids off. I put the truck in park, turned the key all the way off, removed it, waited 10 seconds, and then started it back up. Idle was a little rough, but lined out, and I drove to work with no problems (10 miles). Saw I had the same code again, reset it, and went to work. Drove home ok. Disconnected some hoses and found oil coming out of the PCV valve. I had never changed it, so ordered one from RockAuto. Checked all the vacuum connections, checked the air box connections, reseated everything, and let it sit all weekend. Didn't have any issues Monday, or Tuesday besides a slightly rough idle. PCV valve came on Tuesday, replaced that, cleared code. Wednesday morning rough idle was gone, but the code came back on my drive home from work. When I changed the thermostat housing, I had taken apart the throttle body, but didn't change the gaskets. So I ordered a few gaskets from roverparts, thinking one of them was bad, and it had let go. Truck continued to drive ok, with code popping back up on the 2nd drive every time I cleared it. I could also tell I was missing some power in the 1-2000 rpm range.

Few days go by, gaskets came, took the intake apart, everything was full of oil from the throttle body back... Cleaned out the throttle body, and the intake cast piece. Put everything back together. Truck is running really smooth, but is definitely still running lean, as you can smell it after you park in the garage at the end of the day. Still seems to be missing power in the midband.

I've captured some data a few times with the IIDTool, but only exported it as CSV, and couldn't get times to line up in excel, so deleted it.....

Two nights ago, I decided to make sure the exhaust manifolds were tight, as that could cause a lean code too. The heat shields are... fun... to take off. Everything looked good there. The connections between the manifolds and the cats look good too.
Someone on Instagram mentioned that he would change the ERG valve when they got a lean code (he is a LR mechanic, supposely)... The ERG comes off of Bank 2 and goes into the intake, so wouldn't that show Bank 2 lean? So I also took the ERG valve loose from the intake and exhaust lines, but not the coolant lines and flipped it over and moved the plunger around to make sure it wasn't stuck open or closed, or had any large amount of build up that would mess up its travel. It sprung back to the closed position every time, wiped some carbon off. After taking an hour to get the dumb bolt back into the ERG valve (front bolt in the front of the exhaust connection, need to be a contortionist or something), and dropping the exhaust gasket down into the armor on the bottom, I got it all back together, cleared the code, and started the truck up. Seemed to run fine, so shut it down and went to bed.

Yesterday morning, drove like a dream, the truck seemed to have power everywhere again, and I was thinking that I might order a new ERG valve, but held off to see when the code came back. Code came back on the way home from work. Same symptoms are all back, smooth idle, less power between 1000-2000 rpms, very sweet "lean" smell when parking..

When I got to work, I captured some data, and finally figured out how to export the graphs as a PDF. I converted to a JPG to post here, but the truck is at temp, and I was just reving the idle up slowly. Bottom two are short term fuel trim, next up are long term fuel trims, then EGR stepper position (It didn't open at all?) and 2nd down graph is RPMs. The top graph is everything overlaid on top of each other.

Also attached some pictures of when I had the throttle body and intake casting out...


So that's where I am at the moment. Anyone have any ideas? Should I replace the ERG? I hate to just throw money and parts at it, but I am at my end when it comes to diagnosing what is going on...
 

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Sometimes the tech will distract you from the basics. Most commonly you'll see single-bank lean codes from vacuum leaks, low fuel pressure and dirty injectors. I've owned a long stream of BMW's and I can tell you, each vehicle has its own oddities. BMW is notorious for cracks in their rubber intake tract components. Can't hear them and very difficult at times to see them, but they're there and will drive you crazy. Lean Bank codes are typically the first sign of impending fuel pump failure on these cars.

if I recall from previous discussions on this forum, the LR3 has a replaceable fuel filter tucked in the back under a plastic flap. That would also be a good thing to look at.

Year and mileage info will prove helpful to those more familiar with the LR3 than I.
 

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2001 & 2004 Discovery Series II SE7, with AND without SAI
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146k miles, 2006.

I've checked every vacuum hose I can find. Didn't find anything...
May want to recheck and use a can of Carb Cleaner or WD40 as sometimes cracks can go un-noticed until you hit them with that and get a rev. - unless that's how you checked them.

:laugh
 

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Discussion Starter · #5 ·
Smoke checking an engine with a Viscous coupled fan is...difficult. Didn't find any leaks in 20 minutes of idling, and the light didn't come on for that, or for the 15 miles I drove afterward (separate start of engine too). If I sped the engine up, the fan would blow all the smoke away before it could do anything..

Came on again this morning after dropping the kids off at school.
 

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Discussion Starter · #7 ·
Fuel mixture is controlled via the oxygen sensors and the ECU so I would check if the oxygen sensors on bank one are ok. They have a heater circuit that can fail.
I'm pretty sure that would be a different code.
 
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so in the end did you find out what was the issue?
I am interested as well.
I’m actually doing what you did to your rover. Which is new thermostat housing and cleaning of the throttle body down to the intake manifold since I’ll be removing the parts to install the thermostat housing. I have gasket and new MAF on the way. I replaced the PCV yesterday. Runs better and doesn’t stall since the replacement but the code came back for lean. Before the replacement I have misfires and Reduced Power message.

I have 4 new oxygen sensors but I haven’t installed as I’m having a hard time removing them. They are seized in and pb blaster isn’t helping. I’m afraid to strip them.

I’d love to hear your results on this as it’s driving me nuts too. IIDTool helps remove the code but doesn’t help diagnose.
Have you reset the adaptive values? I did this after replacing PCV and cleaning the existing MAF and it helped the idle and drop in rpm when at a stop sign. Doesn’t stall but the code comes back for lean. Haven’t had reduced power warning.

So for me I’m either going to find out if it’s O2 sensors, thermostat housing and or dirty throttle body maybe even bad MAF. EGR is my last resort as that part is pricy.

only reason I paid for thermostat housing is because it is needed as it’s Leaking slowly at the gasket.

also if you all are looking for parts I go from rover parts to FCP euro and price compare. I like both companies but FCP has lifetime warranty on their parts. Andyou can find genuine but sometimes Atlantic British is cheaper.

last thing is I’m wondering what you all think of removing the entire intake manifold and cleaning? I think it would be a lot of work but Good for the performance after I’ve figure out the code issue.

btw my Rover is 2008 Sport with about 197K it’s been good to me.
 

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Discussion Starter · #12 · (Edited)
With this problem the issue was a crack on the bottom of the intake pipe between the resonator and the throttle body. I fixed it with super glue at the time. I eventually found the problem by buying a smoke tester on eBay that used an air compressor and 12v to blow baby oil smoke out of a nozzle. I pulled a hose off ahead of the throttle body with the engine off and injected the smoke there and found wisps of smoke coming out of the throttle body to pipe connection. After taking that pipe off I found a tiny crack and filled it with super glue and filed it back down to smooth and got a good seal.

In early 2020, I started getting lean codes on both banks, and after replacing that pipe, and again searching for weeks to find anything wrong with a smoker and other diagnostic ways, I sold the vehicle with 162k miles. I was fixing something on the vehicle every weekend and it just wasn’t fun to own anymore.
 

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With this problem the issue was a crack on the bottom of the intake pipe between the resonator and the throttle body. I fixed it with super glue at the time. I eventually found the problem by buying a smoke tester on eBay that used an air compressor and 12v to blow baby oil smoke out of a nozzle. I pulled a hose off ahead of the throttle body with the engine off and injected the smoke there and found wisps of smoke coming out of the throttle body to pipe connection. After taking that pipe off I found a tiny crack and filled it with super glue and filed it back down to smooth and got a good seal.

In early 2020, I started getting lean codes on both banks, and after replacing that pipe, and again searching for weeks to find anything wrong with a smoker and other diagnostic ways, I sold the vehicle with 162k miles. I was fixing something on the vehicle every weekend and it just wasn’t fun to own anymore.
This is the way…

I’m in the same boat. I do get frustrated every time the check engine light comes on. However I somewhat enjoy the search for the problem and the solution, hand in hand. These vehicles are so damn sensitive it’s incredibly discouraging at times.

I’ve got the same issue currently. I replaced the PCV the MAF sensors… now I’m going to look into a bad hoses and connections. This issue has only come up when it’s below 32f outside. So I’d say that some plastic or rubber component has shrunk in the cold and is causing air pressure loss.
The search begins…… continues.
 

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With this problem the issue was a crack on the bottom of the intake pipe between the resonator and the throttle body. I fixed it with super glue at the time. I eventually found the problem by buying a smoke tester on eBay that used an air compressor and 12v to blow baby oil smoke out of a nozzle. I pulled a hose off ahead of the throttle body with the engine off and injected the smoke there and found wisps of smoke coming out of the throttle body to pipe connection. After taking that pipe off I found a tiny crack and filled it with super glue and filed it back down to smooth and got a good seal. In early 2020, I started getting lean codes on both banks, and after replacing that pipe, and again searching for weeks to find anything wrong with a smoker and other diagnostic ways, I sold the vehicle with 162k miles. I was fixing something on the vehicle every weekend and it just wasn’t fun to own anymore.
I had the bank 1 lean code and it was my upstream driver’s side O2 sensor.
 
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