E70 50i engine off when driving, perplexed and needing suggestions
 

Hello,
The site has been helpful before so hopefully someone has an idea. I do my own maintenance so I'm familiar with the X5 and troubleshooting things.

The wife had said her 2012 X5 50i seemed to be missing so I put the scanner on it, and I found no cylinder faults or anything else. I decided to take it down the road myself to see if I could feel what she described.

The drive was fine and I felt no issues. On the way back home at a stop sign I hit it and run it up through first to 6500 and second until around 4500. I felt no miss the entire time.

Then the engine just shut off. No warning lights, no message on the display noting a malfunction, or anything else.

I coasted to a safe shoulder, and tried to restart. It acted like the battery was almost dead slow cranking until it finally started. It ran for about 2-3 seconds and shut off again.

I pulled the scanner back out, hooked it up, and run through all the modules. No fault codes for the engine other than an O2 system error, no specific bank or anything. There was still no CEL on the dash. In addition, I now had a fault on the transfer case for oil wear.

I then tried to start it again, and another slow cranking followed by 2-3 seconds of running before shutting off. I popped the hood and looked under it as well as under the car. No obvious issues so I went back in the car to check all the codes again. Just the O2 system fault as well as the transfer case oil fault again.

I cleared them a second time, and then tried to start again. This time it cranked normally and idled normally. While it set idling I went through the scanner again, and nothing new popped up over the next 5 minutes.

I pulled back out on the road, and it was not accelerating smoothly like normal the first quarter or so. After that, it ran fine the rest of the way home. I accelerated again up the hill moderately with no issues and it was as smooth as always.

Once home I looked at everything again while it was idling. No new faults, just the O2 system and transfer case wear, and I was able to start/stop it normally a few times while trying to reproduce the previous slow crank condition.

I'm at a loss as to what happened. I'm going to investigate the O2 sensor fault a little more to see if it's a specific sensor acting up and change the transfer case fluid so those are done. Beyond that, I have no idea what caused the engine to shut off.

I guess it's possible the transfer case may have been causing a stutter or slight slipping due to the old fluid which she thought was a miss. It was just changed 30k miles or so, but I'll change it again if it says so.

Any other ideas on the cause of the engine off situation? Thanks!

Engine sub-harness issue.


Years ago I recall this a few times with a few cars.



Hard cornering/acceleration would cause torquing of the drive train, connector or wire loose or chaffed.


My guess. Do some google searched for 'engine sub harness' ... see if it matches your experience.

Thank you, I hadn't thought of a potential wiring issue

I'll do some searching on it. Appreciate it!!

Any progress? I think the slow cranking is the big clue here.

Well, I think so

I dived in yesterday. No issues at the battery, just to confirm, but I pulled the lower plate and all the air boxes up top to look over everything well

I haven't found any wiring concerns so far. With searching, it does appear the transfer case oil wear is due to me not able to reset it myself. When I changed it last, I reset apaptations, but it appears only BMW can reset the light.

I did pull all the plugs, and I pulled the pre-cat O2 on back 1 that was throwing the code. I added new plugs and a sensor, and I kept looking for any other possible issues.

I've not found any other problems so I'm putting everything back on this morning so I can do a test drive. I'll drop the oil afterwards when warm, but so far only the plugs looked rough with 70k on them and the O2 definitely looked like it was seeing a rich condition.

Otherwise, my investigation continues

Well, this is not the update I wanted to write.

I got it all back together, cleared the codes, and then started it up. It cranked fine, and I let it idle for 15min or so to see if anything came up. No codes so I decided to take it down the road.

For the first couple of miles all was ok, and then with the cruise on it started to accelerate as I went up a hill. It made a single "thunk" sound, and I turned the cruise off real quick. As I was slowing down, I heard a high pitched tapping sound. As I slowed down and pulled over, it sound more like something flopping around as the rpms settled. Maybe similar to a rock in a can, high pitched and not a consistent rhythm.

I got the wife to come get me and the X5 so it's back home now. Using my stethoscope, it's definitely on the bank 1 side and when it made the sound on the road it did trigger the pre-cat O2 bank 1 too rich fault again.

I'm going to pull the air boxes off again on that side, and I wonder if I lost the bank 1 pre-cat. I've had a cat break up before and it did sound like rocks in a can. Or it could be the turbo I guess as well.

The only fault is the bank 1 pre-cat is too rich, and otherwise the X idles seems ok other than the rattle. Nothing else seems to be affected or seeing an issue. Figures.....lol

With the slow cranking it almost sounds like an engine timing/chain issue.

If nothing is really obvious maybe pull the plugs on that side to see if there is mechanical damage.

Ok, I'm back at it. I got all the intake and such removed on the bank 1 side. At this point I'm trying to figure out how best to attack.

I'll pull and check the plugs first just to confirm nothing obvious in the cylinders, but the noise does appear to be coming from the primary cat/turbo area. It seems to ve echoing pretty good on the scope when I listen.

I may start it after checking the plugs just to see if I can get a closer listen to it with the air box out of the way.

Is it possible to pull the bank 1 primary cat without pulling the turbo? I did some Google searches, but I didn't see a walkthrough that shows if the pipes may be replaced without pulling everything around it off or not.

I'll update later.

Looking at this thing, it may be worth pulled the bank 1 turbo since that may need to be removed anyway if the primary cat has to be pulled. With the turbo out id the way, I will be able to stick a camera up the cat to see if chunks are broke off.

All plugs removed, and they look fine. A little rich on cyl2, but the rest looks ok for day old plugs. No damage to the tips or anything else.

Ok, I got the O2 sensors out and pulled the heat shield off the primary catstl.

The bank 1 post cat O2 sensor was covered in white powder, that's not normal. I checked the bank 2 post cat 02 and it had some white powder on it as well, but it wasn't as thick as bank 1.

The new pre-cat sensor in bank1 still looked pretty new since it only had around 5 miles on it. Tank w pre-cat sensor had a little white residue but nothing weird like the post cat sensors.

I'm still thinking I may have a bad cat or 2? I pulled the front coupling off the bank 1 turbo and it's clean. Nothing seems to be getting up there. It did appear the rattle was coming from the upper back of the engine.

Any concerns trying to start the engine with the O2s to see if any residue flies out of the post cat sensor openings? I'll listen again for the racket, but I'm thinking if the cat is breaking apart it will be going toward the post cat sensor and not toward the turbos.

Thoughts?

Ok, I moved around it as quick as I could listening and I have to say it doesn't appear to be coming from the cats.

Again, only code is bank 1 pre-cat is saying too rich. Otherwise nothing else is showing.

Here's a quick video as I was looking and listening. With all the stuff out of the way, I have to say it seems to be coming from the valve cover area around cyl 1 or 2. So I guess that cover is now coming off.

Again, it's not a deep motor sound like a rod. It's high pitched and inconsistent. I would say it's a bent pushrod if this was my LS car

Hmm, thinking out loud again. Does the Vanos tap without a rhythm when bad?

Here's the link to the video. I was looking around trying to isolate it so sorry for all the movement. It appears to be from the front area, not heard from underneath at the oil pan, and the back of the engine by the cats not much there either.

https://youtu.be/55gdrGGZMZk?si=NOFPIMGI1Ij6xG6K

OMG. I would not be running that motor. Not even for a little bit.


Your issue is not a air filter; not an O2 sensor; not a CAT.


Open up the timing chain cover. Look for bits. if you are lucky (and you dont keep running it and break a chain, crash the valvetrain) maybe you are lucky and new chains and guides will fix it.


It also doesnt sound like a vanos issue

Timing chain and guides? Never heard one tapping like that before when bad, and this isn't my first BMW. Would I not be seeing cam position sensor faults if so? Not debating, just trying to learn since I never thought of chains/guides as a potential root cause.

I didn't realize the chains and guides were a concern on these N63, but I know my M62 can have issues.

If the guides are trashed, will they show bits in the oil pan like on an M62? I can drop that tomorrow easily. Thanks!

I don't know if it applies to these engines but on some the crankshaft timing gear is held in place by the front damper/pulley with only a small pin or key holding it in position till the pulley gets torqued, if the pulley comes loose the tiny pin/key partially shears and the engine goes out of time randomly until it swallows valves. So something else to check( pulley loose) and that is consistent with the sometimes hard cranking.

When I hear odd sounds - like metal bits- from inside an engine, my first instinct is to open up a path to the oil and have a look see.


I think your idea is a good one.


I have ZERO personal experience with your motor.



Years ago I had a Q45 V8 which I bought new. about 10 yeas and 150k in, I started hearing an odd ticking up front. Parked it. 6 monhts later, when I got around to it, found two broken valve guides- still enough there to prevent wild chain slap (and catastrophic failure). I was so so lucky. $2k in parts and I drove it another 150k miles.


GL!

Well, I'm flying out today for work so this one will have to sit until I get time to jump back on it.

I didn't see any guide parts in the oil pan, and there is no metallic glitter in the oil. So at this point nothing is telling me anything truly negative. I reinstalled loosely in case I need another look before I'm done.

I got all the heat shields back on and covers so I don't leave it mess. Mainly I'll worry about forgetting where everything goes before I come back. I did pull the oil fill and peek in with a light and camera. The top bank 1 chain guide is still there in one piece so that doesn't appear to be it. Where I could reach there is still good tension on the chain so that's a plus that maybe the bank 1 tensioner is also still there.

I'll pull the valve cover when I return, and while I'm gone I'll do some goggle searches on removing the upper timing cover for a better look.

Thanks for all the help and suggestions so far. I'll update this thread when I get back on it in a few weeks. That will also give me time to order some gaskets to put it back together.

Well, I heard from a fellow BMW owner that I should look at my HPFP just to verify it's ok as he said his made a similar tapping sound when it was going out. He first thought the engine went bad, but he had no video to share with me.

If it was a bad HPFP tapping, would it not be throwing codes? Just trying to rule this out for sure. I'm going to order some parts when I head back home, but I can't order everything. Lol

Anyone heard an N63 HPFP tapping when going out? If so, does it sound similar to mine or different?

Ok, I also found this video and this does sound like my tapping sound. It's diagnosed as a rod knock in this video, and it doesn't start/stop like mine. I didn't see anything in the oil and pan, but it may be because she didn't drive it once it was heard.

https://youtu.be/FW42V5au7Vs?si=BuTN55tMDpiG8z9a

I'm just not seeing any knock sensor faults or anything else which is weird if this is it

Your noise seems to be connected to the engine revolutions it just comes in and out. What does it sound like when you increase the throttle a bit? I think that rules out HPFP, unless that's mechanical ? and rules out turbo and cats. Are you sure your scanner is reading all the codes and not just OBD ones? I find videos/recordings are often not as good as being there so you are in the best position with your stethoscope (and maybe try a piece of hose) to try to pinpoint things. The hard/slow cranking is still a consideration as well.

Im not sure why a 'knock sensor code' would enter into this conversation at all. Rod knock is not something a pre-detonation sensor would pick up. IMO

Thanks, I know internet investigations are tough.

When I touched the throttle, the tapping didn't seem to increase in frequency with rpms. The engine revved up fine even with the noise.

I'm using the NT510 to read the codes. It seems to pull everything quite well, plus there being no CEL on the dash with only the O2 code being found gives me some confidence.

It's not hard/slow starting now. It only did that when it shut off unexpectedly. Once I let it set 5-6min or so it started back up and drove fine afterwards. No codes were thrown then either other than the rich bank 1 O2 which seems odd

I can only hear the tap at the top near the head. Underneath at the block or pan, I don't hear it with the stethoscope so that's 3hy I didn't think a bearing, but who knows.

Thanks for your thoughts, all suggestions are appreciated!

Try the hose trick, sometimes that is better at giving a feel for where the sound is coming from because it's not picking up as much of the sound being transmitted through the metal or plastic.

It was shown on the video I linked; a knock fault along with a misfire fault, and a few other codes I'm not seeing.

It wasn't just about the knock fault, but I guess I could have worded it better.

Got it. :thumbup: