Intake manifold is off, working on vacuum hoses

[sunny_j]

Originally Posted by TriX5

....where have they been all this time? Decided to take it iff the jack stands and give it a whirl. The improvement in performance is insane! I even have brakes again! So, I guess my vacuum system was seriously messed up. Cleaning up the intake and swirl flaps probably also made a significant difference.

I saw some posts of people with E90s who had a lot of improvement from changing the pressure converters. And this tallies with that experience. I am so pleased that I decided to tackle this at last.

Next stop, transmission and TCase service.

I changed the pressure converters and electronic valves when I did the VCG back in December and I noticed an improvement in throttle response.

[TriX5]

Mine feels transformed, but I am at higher mileage and I had been advised several times to replace the vacuum lines. But....the estimates were typically not far shy of 1k which is too much.
I feel that a trained mechanic could do this in three hours if only the hoses are replaced. Even including taking the manifold off. Replacing the converters and valves would take another hour at most.
Cleaning up the IM Is quite a bit more time consuming, possibly another three hours but it does need to be soaked for 48 or 72 hours at least.
This job is like most other jobs on the X5, once you have done it once it is a lot easier to repeat if need be.

[TriX5]

....all the error codes are gone and so....two codes refused to go away even after the big vac replacement job.

One is the pre-turbo exhaust manifold pressure, the other one a denox sensor. The former has been a constant but getting worse. There are two other codes but I think they result from these two.

Today decided to tackle the former and check that the back pressure pipe is not clogged. Removed the back pressure pipe and fiddled a bit poking a wire thru it. Then thought some compressed air would be good......stuck the air nozzle into the bit of rubber hose and, guess what? Air coming out everywhere from the rubber hose. Leaks like a sieve.

Though a bit of hose would suffice, decided to just replace the whole part as I need new seal rings for the banjo bolt and a few small parts to put the front pan on the bottom back. (Why do "the pros" always lose one or two of the quick release screws and then not bother replace them, aaaarghhh)

I have the sneaking feeling the denox sensor is bad but I prefer to replace one item at a time so as not to confuse myself.

Back to waiting for parts. (Maybe I should try wrestle the gear shifter out of the car as it has a bad switch and its replacement arrived last night. :-)

[TriX5]

Replaced the tube for the pre-turbo manifold pressure sensor and replaced the EGR cooler (for the third time!). That took care of two codes.

EDIT 1: Found one post on another forum about a case that said, the EGR bypass flap sticking was caused by a coolant leak inside the EGR cooler, which screws up the shaft on which the flap is mounted. I did note a slight coolant loss over the past year but it was very minor. Definitely seems like my case.

Now, once the engine warms and has been restarted a few times, I still get the downstream Denox sensor code, sensor out of range (post cat). It says the oxygen reading is too low on the over-run? It is not a constant error and the sensor doesn't seem to be totally gone. I am wondering if it is the sensor or something else, SCR maybe? Guess I will start by removing the downstream sensor and cleaning it.

EDIT 2: There seems to be an adaptation set for the functioning of the SCR that is reset by the tech when ever the shop fills the tank. So, I might try and fill the SCR tank and see about resetting the adaptation and if that offers no solution then remove and clean the sensor before replacing the NOX sensor (they are both original to the car....).

If that fails I will have to decide if I can get a used one, replace the probe part (solder it onto the existing electronics) which is about $70-80 or spring for a new one ($300). Anyone gone the route of replacing the probe?

[TriX5]

Managed to crack the rear NOx sensor free! In the next few days will make time to remove it and clean it up with injector cleaner. Also, managed to install ISTA/D on my laptop and now I can run the test program for the NOx sensors.

EDIT: Yesterday took out the rear NOx sensor and cleaned it then put it back on the car today. Then did the brake bleed using ISTA and my home made pressure bleeder. After completing that task, back to testing the NOx sensors.

After playing with software and driving the car for a bit I realized that the rear NOx sensor is completely dead. So, time to get a replacement.

[TriX5]

To close out this thread. Replaced the downstream NOx sensor with a used one, car still refused to reset properly. I had bought yet another NOx sensor since I wasn't sure about the first one being ok. Not sure why my gut told me to get a second replacement but it turned out to be the solution. Now I have an NOx sensor with 35k on the car and all is well. (The seller of the first/faulty NOx sensor refunded my money, happy with that.)

Note: ISTA is not very straightforward to use for this but once I understood it, it helped a lot. On replacing the NOx sensor, the SCR system needs to be reset/sensors initialized, which is a completely separate routine in ISTA. Once you reset the SCR, the pre-SCR temp needs to be brought up to >150C and only driving the car will get the temp up there. Up to that point the SCR system doesn't release readings on the NOx sensor. Have been using the car for a week now and no more faults. This has been one of the most convoluted fixes ever where fixing one problem simply led to finding the next one.

Since it came back from Europe early June, I replaced:
MAP sensor
CCV hose (AARod)
Vacuum lines (every inch of it)
2 Vacuum valves/3 pressure converters
Vacuum reservoir
vacuum pump seals (DUDMD)
IM seals
Hose parts of the main vac lines to the brake booster
Steel line/hose to exhaust manifold pressure sensor
EGR cooler
Nox sensor (rear)

Also, cleaned the intake manifold, performed trans and TC fluid change/reset.

The MAF sensor, EGR valves, differential pressure sensor and exhaust manifold pressure sensor were all replace 10k earlier. The DPF was removed and cleaned at the same time.

In a nutshell, since ~125k there have been a plethora of issues gradually getting worse. If I was in the same position again, I would pull the engine/transmission/sub-frame in one go and do all of this (and add the mech sleeve, engine/trans mounts and valve cover/oil pan gaskets) in one go. Yes, that is major surgery but from the accounts on here all these items will come up anyhow and working on the engine and trans once it out is so much easier and saves many hours that otherwise are spent wrestling with stuff that is incredibly hard to access.