Well, recap time. First, these engines are STUPID sensitive to vacuum leaks. As you probably know too well by now..

How old are the O2 sensors?
How old is the MAF?
How old is EGR valve?

Places to look for leaks:
Intake plastic tubing downstream of MAF - these cracks can be hard to spot. Also critical to never crank down on the worm clamps.
Throttle body gasket to intake plenum (plenum is the metal piece between the intake and throttle body). New gaskets should be used, if not apply THIN coating of sealant.
EGR gaskets - there are two - again, coat with sealant. There is one at the plenum and one on the underside where the EGR tube attaches.
ERG ***-end - way behind the intake there are two 8mm (maybe 10mm?) bolts that connect the EGR tube to exhaust. These can loosen up. Check em.
Oil dip stick o-ring. Its at the top fo the stick, easy to replace with something that fits.
Oil filler neck o-rings - there is one at the base of the neck and one on the filler cap itself.
Various o-rings at the crank case ventilation tubes - there are two tubes, one coming from the PCV valve and one bridging over from the other side. There are o-rings on each end.
PCV valve itself I *think* has an o-ring at its base?

The above is all I can think of for the common basic leaks. Below are less likely to leak, but ya never know...
MAP sensor (not MAF) is on the back of the intake. A pain to get too. Make sure its bolts are tight. Careful with connector, I broke mine.
Behind the intake plenum and on the front of the intake manifold is a large green gasket. If the plenum was removed, this could have been damaged.
There is a similar gasket above on the rear of the intake behind a cover and above the MAP sensor.
Valve cover gaskets - I guess just make sure valve covers are tight.
The intake itself is comprised of three sections, large plastic body and each side has metal "runners" or such. There are gaskets between all. These are not oily to leak if the intake has never been pulled.

Above was all off the top of my head, there may be more stuff.

Oh yeah, there is more. Have to ran it with the brake booster disconnected/plugged? The brake booster is the only external vacuum system on the engine. Its equip with check valves I believe. But if the brake booster has a leak, that would basically mean an engine leak. The black plastic tube comes off the rear of the engine.

 

Thanks Dakota.

I’m not clear on the brake booster disconnect thing but I’ll research and work on the rest.

Out all weekend in the mountains and snow and it’s been doing good. Light on and same codes but nothing I can do other than clear them until I get home.

 

The brake booster is an aid to help with braking. Without it, its very difficult to stop the truck. Typically brake boosters are vacuum operated and the best source for vacuum is the engine itself. So if the brake booster has a leak or if there is leak in the line, well then you have an overall intake leak. The brake booster vacuum hose it shiny black and comes from the back of the engine to the booster itself which is located near the ABS module. The booster is large, round and black on end, just behind the brake fluid reservoir and master cylinder.

 

Awesome description, thanks.

Can that leak be found with a smoke test too? I’m going to go ahead a buy a real smoke machine instead of my crappy homemade one to start again, then go through all the steps you listed.

 

This is an excellent question and point. I’ve subconsciously thought my brake booster or hoses too and from the booster are leaking. I frequently have had poor stopping power… but then again my brakes are in poor condition.

I haven’t had a chance to put the top of the engine together yet. My injectors are refurbished now and are like new. The injector cleaning specialists was surprised at how well these original injectors were for the 160k miles. I have photos of the spray patterns I’ll try and upload soon. Injectors are NOT my problem. I’ve got a vacuum leak… somewhere.

I got to talking with the injector specialists for a while about this code, 171/174. He said that 90% of the time it is a vacuum leak. 5% off the time it’s the fuel injectors and 2% it’s the break booster and 1% is the fuel pump. Very rarely it’s the MAF or PCV, which is the remaining percentage in this guesstimating. Oddly enough the MAF and PCV are the first things we’re always told to look at.

My next steps include. Cleaning the intake manifold, cleaning the intake cylinder’s, replacing all gaskets on the intake manifold and EGR, replacing the PCV hose, replacing the PVC hose Left Valve Cover To Intake. I’ll reinstall the original fuel injectors… which are fully refurbished, filters and O-rings.

If none of this mentioned above will fix the 171/174 codes. Only thing left to look at would be the fuel pump and or the brake boosters and hoses.

i know in theory how to test for a bad fuel pump. However I have no idea of how to test for a brake booster or hoses.

A good bit of advice. My injectors specialist highly recommended using WD-40 to find vacuum leaks on the hoses. In his personal opinion it works 100 times better than any starter fluid or carb cleaner. Which I tried carb cleaner on hoses and did not find any devotion of the RPM’s.

 

Some modern carb cleaners are not flammable.

Brake booster is easy to check, pull a vacuum on it with a gauge and see if it holds.

 

I’m still struggling to find the issue with my LR3. I’ve started calling mechanics to make an appointment. Most are out by the or five weeks. I fully cleaned and put together the intake manifold and replaced a couple vacuum hoses. The CEL light was only off for 1 day. She’s back! I figure now I need to use the propane method and look for the vacuum leak. My two long term trims are about constantly 4-6 points different.

Anyone a semi expert on the fuel trims?

 

'aight - I finally got a good smoke test and noticed the following:

• immediately, the top of the EGR, where the silver meets the metal leaked smoke. The oil filler cap was off cap was off.
• eventually, a short time later I noticed smoke from both the left and right lower portions of the intake manifold (? I think ?) - photos below. The oil filler cap was off cap was off.
• when I left the oil filler cap on and let it build a bit of pressure I got a lot heavier leakage from both of the above.
• when the pressure build a bit more I got some leakage from the air intake resonator. I then released the oil filler cap, dropped the pressure and stopped.

So I guess (with your help) I can confirm that the entire thing is leaking all over the place and needs an entire intake manifold reseal using the British Atlantic kit here: https://www.roverparts.com/engine/kits/9218D/.

Should I try doing the EGR first before ripping the top of the intake off? Or, should I go ahead and reseal it all with the kit and then find a new resonator or just go the RRS route with the straight pipe? Finally, do I need to do a final smoke test after a full reseal?

Now for photos...



EGR: leaking from the top area that the two parts bolt together.

Driver's side smoke leak.

Passenger side smoke leak (rear'ish).

EGR: more specifically where the leak is on all sides of the two parts.

Passenger side smoke leak (forward'ish)

Smoke leak from resonator.

 

That’s a pretty successful smoke test. What smoke tester did you end up using? Where did you pump the smoke into?

I bought a new resonator from Brutish Parts of Utah for about $160. The Atlantic British intake manifold kit is great. They’ll take back any parts you don’t end up using too. The EGR comes with two new gaskets in this kit. Word of advice, remove the entire intake manifold and injectors as a single unit. After you remove all that as one unit it’s so much easier to pull injectors from the manifold on a work bench. Always clean your injectors too. Send them out or find a local shop. Very, very seldomly will you need to replace an injector. When you take your intake manifold off… take a straight edge like a framing square and make sure it doesn’t have any warps.

Removal of the intake manifold took me about 1.5 hrs. Cleaning the manifold took about 4 hrs, dry times included. Reassembly of everything took about 45 min. Not bad really. This was however, spread across two weekends. The hard part was removing everything without breaking any plugs or weak plastic. The scary part was putting all the nuts, bolts and screws back into this old plastic without stripping anything. I only used hand tools and followed the specs with a torque wrench. I know I still over tightened some screws and bolts. This is what makes me worried.

 

My 2008 LR3 with 216K miles had the following codes:

P0308 Cylinder 8 Misfire
P0316 - Misfire Detected on Start-up
P0171 - System too Lean (Bank 1)


Occasionally I would get misfires on other cylinders as well.
Car would have a slight puff of gray smoke while running.
Previous owner told me that all the parts are original.

On initial start the idle would be really rough as the engine misfired which would then smooth out later.

I first replaced the PCV valve, MAF sensor, put in new NGK spark plugs and Delphi ignition coils. I cleared the codes and reset the adaptations. It seemed to run fine for a few days but the CEL came back on. I then cleaned the throttle body, without removing it and cleaned the fuel injectors with BG44K through the fuel rail.

The CEL returned so I did a smoke test. I noticed that there was a bit of smoke coming from the EGR. I did another treatment of BB44K, this time in the gas tank. The CEL remained.

This time I removed the throttle body completely and noticed the passage in the throttle body to EGR was very clogged up with carbon. I cleaned it out, and cleaned the EGR valve as well though it didn't appear to be sticking. I looked inside the intake manifold and noticed a lot of oil, like a full quart. I cleaned it all out. I installed new gaskets for the EGR. Did the thermostat housing too while I was at it.

This didn't fix the CEL, I was still getting misfires on Cylinder 8 though the lean code was gone. In fact, I think it was misfiring more often than before. Next, I changed both upstream O2 sensors with Densos. I cleared the codes and ran it. On each start, the CEL would return. Using my scanner, I could see that cylinder 8 was misfiring quite a bit on start, with about 50 - 100 misfires, but then the misfires would stop as it ran. Previously the car would run a while before the CEL returned. This time, it returned immediately upon the 2nd start after clearing the code.

I pulled the coil and spark plug for cylinder 8 and noticed that the electrode was covered in oil, even though the plugs are new. I cleaned it off with a wire brush and MAF sensor cleaner and reinstalled. I cleared the codes and this time reset the adaptations again. The CEL hasn't returned in the last 300 miles. I'm hoping it's fixed!

One interesting thing I noticed is that the LT fuel trim for Bank 1 was originally around 3% at the start and by the time I replaced everything it's been around 7%, with a negative 3% SFT. The LTFT went up but at least there's no CEL. The engine doesn't misfire when I start it anymore too. I just noticed this morning that there's no smoke coming out the tailpipe.

So I'm thinking that whatever was wrong with it caused the Cylinder 8 spark plug to get coated in oil. Perhaps I had fixed the issue earlier but since I didn't clean the spark plug the CEL would return even though the problem was fixed? I figure with 216K miles, it was worthwhile to replace all those components I did anyways so I don't feel bad about replacing something that wasn't causing the actual problem.

Now I just need to figure out the TPMS light. I replaced the module but the TPMS light is still on!