Well, as I said, over 2 years with nothing, now perhaps something in the right direction. Interestingly enough there's a TSB issued in 2019 for the SC V6 regarding a PCM software issue and the P0089 DTC it now has.

EDIT: other notes indicate a possible fuel pump problem or sensor issue.

https://static.nhtsa.gov/odi/tsbs/20...54041-9999.pdf

 

I had this code pop-up one time when it was under warranty, and the dealer did the PCM update. Never showed up again, and I never had any symptoms from it. With your issues, could be the pressure regulator or one of the fuel pumps failing. The HP fuel pumps can also leak fuel down the shaft and into the crankcase as I understand it, which might explain the fuel in the oil.

 

I've to decide what's next. I've recently spent nearly as much as the truck's trade value in repairs. There are several other recent mechanical issues which have popped up (suspension compressor works but has become very noisy and I think, runs more often that it should - air springs are fine as it can sit for days with no change in height; the park brake occasionally triggers 2 MILs and a couple of DTCs; possibly other pulleys needing replacement, etc) and I fear more failures could come along at any time. I've spent the last 2 years with the main dealers for the idle issue with no resolution and still don't know what the cause could be (perhaps closer now) or how much more it will cost. Despite the miles, other than some stone chip on the front bumper and mirror caps, it's in perfect condition cosmetically as I'm rather meticulous and OCD. Most vehicles I keep no more than 2 years, but the 4th generation Discovery's has been a favourite and I loathe to let it go but it's also just a vehicle and I've to make the right fiscal decision as to whether to carry on or move on.

 

Ran a few routines in SDD today. Engine idling VERY rough consistently now, MIL still lit. Tried the purge valve test routine, evaporative emissions test routine, high and low pressure fuel pumps routine, commanded vs actual idle routine, and some others. All passed without faults but what is very bizarre is SDD can not find any DTCs, stored or historical, related to P0089 and while running the routines, the MIL indicator went off...

Interesting note on the idle test routine, if I command an idle of say 900, 1400, 700 RPM, the actual RPM stays at 700 or any other set RPM +/- 5 even with piling on the accessories and with no shudder of course, HOWEVER if I command an RPM of 600 RPM, the actual RPM is all over the place from 500 to over 600 and of course the engine runs rough.

 

So, the MIL went off during testing. Did it come back on after testing? Or is it still off? No idea why it wound’t store the code.

The idle test still seems to be consistent with a fuel mixture control issue. It shows up at low RPMs more than higher RPMs. Car might even be in open loop at those higher RPMs. The test is just commanding a throttle position, it’s not controlling the fuel mixture.

Not sure what all the routines do, and what they look for.

 

It never returned and P0089 went from being to a stored to to no code whatsoever, not even historical. You're correct regarding the RPM routine, I was simply reinforcing my observations that rpm below 600 induces rough idle, whether commanded or on its own.

Meant to also say the hard acceleration rattle (which sounded like knocking in retrospect) has yet to occur again since the day I noticed it.

 

Perhaps I may have missed it in the past, but sometimes I do listen for it and have never noticed it but today for the first time I know of, I heard the pump run for several minutes after shutting the car off. Is this normal or is this an indication of a failure? I tried to get it to do it again but was not able to get the pump to run again.

 

Oldman846 and I were debating this behavior a while back. I started noticing my pump running more often over the last year, as did he. I never came to any conclusion as to whether it’s normal or not, but I expect that it is normal.

There is a section in the manual that is dedicated to the EVAP system - Section 303-13A - a section that I do not have. I know the DMTL pump is supposed to run at some point after the ignition is turned off, and there are other conditions that need to be met (car was driven X miles, so many drive cycles since last test, fuel level in some range, etc.) but I don’t know the specifics. I also believe the DMTL will re-run more often if it is unable to complete its test for some reason, and if it can’t complete its test too many times in a row, a DTC will be triggered. At least that’s my understanding.

I’ve been meaning to go into TOPIX and find that section of the manual, but just haven’t done it yet. I just figured the DMTL is running more now (in my case) because my driving conditions are so different with the pandemic than they used to be. Lots of short trips - more driving cycles - etc.

Had one other thought based on postings in the other forum - have you checked/replaced both your coolant temp sensors? How long does the car take to reach temp based on the dashboard temp gauge? It should reach temp within about 5 mins based on other reports and my own experience.

 

Had another MIL with P0089 DTC today.

Monitored ECT. When driving it's at around 214F, sitting stopped at a light it drops to 199F. Sometimes it bounces up and down. Also checked catalysts' temps. Both stayed around the same although one of them at one point had a 200 degree difference. They kept bouncing up and down between 400F and 900F. Engine idle also fluctuated greatly today. Stopped for a while and sat at 630, then jumped up to 1150 and stayed there for a while, then dropped to 800 for a while then jumped back up to over 1100 then dropped to 610, continued this bouncing up and down all day.

 

All searching for that code, across multiple forums, points to LR015356--fuel pressure sensor. For some, the PCM update worked. Others state that it worked for a short period and replacing the fuel pressure sensor ultimately fixed it.

I find it odd that your ECT temp would decrease when stopped and increase when moving. However, a lean condition may cause this, and the cat with the higher temperature would indicate the affected bank. A defunct fuel pressure sensor may inform the PCM to not add enough fuel. It is surprising that it would affect only one bank.

Affecting fuel to one bank would lead me towards a MAF or High pressure fuel pump. The other sensors are variables to the fuel table in totality.

Update to my post on the other forum, my DMTL pump still runs for long periods occasionally after shutdown. I'm in the "ignor it" phase. If all of us are experiencing the symptom, it may be normal.