BMW X3 xDrive28i N20,146k, 7.5k M1 Euro OW40 , high wear

I idled the car for a awhile to get it warm before taking the sample. It wasnt full oil temp. wasnt a complete cold start since the car had been driven 3 hours or so earlier. I understand this isnt ideal but with kids the time i have to do this stuff is at night after they are in bed, in the dark, with a flashlight...

Here are some reports that look ok for this engine but have lower flashpoints as well. Not sure what to make of it. This car gets driven for 30-40min in city traffic twice a day then has fairly frequent highway trips. Oil temps on these cars can be in the 240F range on the freeway.

I have no idea how one diagnoses a DI injector for this type of behavior.

385F flashpoint. Trace fuel finding

370F, 0.8% fuel

380F, trace.
 
Perhaps dirt ingestion through the air intake would just cause wear in the bore (iron and al) and not make it to the bearings since those are post oil filter? Then again the piston rings do have a chrome coating and we do not see it...perhaps that coating is long gone.
Chromium does seem to be elevated. It's 1 ppm vs the universal average of 0 ppm. Of course, there isn't enough precision in these numbers to know exactly how much higher than normal it is, but for all we know there could be 10 times the normal amount of chromium in the oil.

When dust gets into the intake, it does wear the rings, liners, and pistons more than anything else, since they're exposed to it before it can be filtered by the oil filter. Elevated silicon, iron, aluminum, and chromium is exactly what you'd expect if air filtration was the issue.

I'd expect to see signs of dust in the intake piping downstream of the turbo if the PCV connection had a significant leak. If you have a scan tool, check your fuel trims. They'll be reading high if there's still a vacuum leak somewhere.
 
Also the plastic guides rubbing on aluminum can cause findings of same. It doesn’t have to be the chain. Interested to see the measurement result.

Understand flashlight car work. A guy started a business based on it. UUC. Used to have a guy with a flashlight as a logo. :)
 
I logged data on a few drives and found that under constant loads the engine is targetting the same amount of fuel per injector. It strays apart a bit during load changes which might be the engine trying to close the loop per cylinder or probably more likely when the sample is taken since its pretty low data rate. I have no idea if thing ECU tries to do per cylinder fueling. Seems like that would be hard to do with the O2 sensor being post turbo. I'd call this inconclusive.

Long term fuel trim on the freeway warmed up is near 0. Around town ive seen as high as 10% when cold and but that settles down when in the low single digits. It is always positive though. The long term fuel trim update period isnt all that long. It probably has a 5-10second period. I didnt see any sort of longer term trim that was global in the data available to me. Just idling the engine the long term fuel trim lands in the 4-5% range often. Since i do not have a reference point this has me thinking. a small air leak would show as a greater % at low loads like idle. Though i cannot find one with a smoke machine... or well this could just be the 10 year old MAF and O2 sensor...

This engine is nearly always under some sort of positive intake pressure. Being a valvetronic engine, the only place vaccum should occur is pre turbo.

Next step i am going to do is put a new PCV hose on it. I broke a clip on it and the turbo inlet tube too has some issues with the features the PCV clips snap into. So I'm just going to replace both. I have a set of charge pipe seals on the shelf that i never installed from when i did the turbo. I'll take a look in the pipes for debris when i do that. I think i need to look at the air box one more time too. with the headlamp shinning right at it, it had some really small dust on it and when i wiped the clean side of the box with a paper towel it came back grey. I think that is from combustion products in the intake over time but this all it making me rethink that. I studied it visually for defects and found nothing wrong with the filter or box or how it went together.
 
I logged data on a few drives and found that under constant loads the engine is targetting the same amount of fuel per injector. It strays apart a bit during load changes which might be the engine trying to close the loop per cylinder or probably more likely when the sample is taken since its pretty low data rate. I have no idea if thing ECU tries to do per cylinder fueling. Seems like that would be hard to do with the O2 sensor being post turbo. I'd call this inconclusive.

Long term fuel trim on the freeway warmed up is near 0. Around town ive seen as high as 10% when cold and but that settles down when in the low single digits. It is always positive though. The long term fuel trim update period isnt all that long. It probably has a 5-10second period. I didnt see any sort of longer term trim that was global in the data available to me. Just idling the engine the long term fuel trim lands in the 4-5% range often. Since i do not have a reference point this has me thinking. a small air leak would show as a greater % at low loads like idle. Though i cannot find one with a smoke machine... or well this could just be the 10 year old MAF and O2 sensor...

This engine is nearly always under some sort of positive intake pressure. Being a valvetronic engine, the only place vaccum should occur is pre turbo.

Next step i am going to do is put a new PCV hose on it. I broke a clip on it and the turbo inlet tube too has some issues with the features the PCV clips snap into. So I'm just going to replace both. I have a set of charge pipe seals on the shelf that i never installed from when i did the turbo. I'll take a look in the pipes for debris when i do that. I think i need to look at the air box one more time too. with the headlamp shinning right at it, it had some really small dust on it and when i wiped the clean side of the box with a paper towel it came back grey. I think that is from combustion products in the intake over time but this all it making me rethink that. I studied it visually for defects and found nothing wrong with the filter or box or how it went together.
BMW always programs software in such a way as to not tolerate high discrepancies between O2 sensors. So, you will get CEL for O2's or MAF if they're slightly out of sync.
 
I idled the car for a awhile to get it warm before taking the sample. It wasnt full oil temp. wasnt a complete cold start since the car had been driven 3 hours or so earlier. I understand this isnt ideal but with kids the time i have to do this stuff is at night after they are in bed, in the dark, with a flashlight...

Here are some reports that look ok for this engine but have lower flashpoints as well. Not sure what to make of it. This car gets driven for 30-40min in city traffic twice a day then has fairly frequent highway trips. Oil temps on these cars can be in the 240F range on the freeway.

I have no idea how one diagnoses a DI injector for this type of behavior.

385F flashpoint. Trace fuel finding

370F, 0.8% fuel

380F, trace.
No Blackstone analysis is reliable in terms of fuel dilution. Not even close. That makes any viscosity deviation indeterminate between fuel or mechanical shear of the VM.
 
No timing chain noise or changes in inside of engine noises in the time weve owned the car (112k - 147k).

Im still marching down the dirt in the intake path. I pulled the turbo discharge to the intercooler off the other night to take a look. I did find a few specs of granules of something that could be dirt. Everything inside is covered in a film of oil since the PCV dumps upstream of the turbo. If the engine was ingesting fine dust its going to be hard to spot. I did notice the OD of the inlet pipe near the turbo has oily film on the outside that doesnt have a clear source. perhaps theres a crack there.

Ive got the PCV hose and a new inlet in the mail. Plan is to replace those, pull the charge pipes and take a look inside those and replace the seals on the charge pipes as well. All those mating joints have signs of oil around them which of course indicates some level of leakage. Probably do another smoke check on everything since i have the machine.

Since then the wifes been driving the car. i got the results back at around 1200miles on this oil change. Thats when i corrected the seating of the PCV interface. By the time i get this parts on the car itll have around 2000miles on this oil change. So i am thinking of doing a oil change now, send it out so i can reset things to see if this work corrects anything. Perhaps send another sample from this fresh change in 1500-2000miles? One issue with all this is that it takes way too long to get results back from blackstone. has anyone had anyluck asking them to do it faster or have a reccomendation for a faster lab?
 
Took apart and inspected the entire intake track. Found some specs of what i think is dirt in the pipes. If there was fine dirt in small quantities it wouldnt be noticeable because of the oil film from the PCV system. I found no cracks or anything that would be letting in large amounts of dirt. That unseated PCV hose i talked about earlier would have been it, if anything.

Replaced
-PCV hose
-Turbo inlet
-All seals on pressure side VDA fittings

Timing chain passed the elongation tool test. Found images of new vs old parts and can visually confirm the tensioner and chain are the revised parts. So that can be completely ruled out now. I am pretty sure the timing jumped on the exhaust cam while doing the test though. I followed the bmw procedure but somehow while i was rotating the engine by hand with the measurement tool installed it suddenly popped and the tool transitioned to reading a lower but very passing value. My guess that is that was the chain making its way the rest of the way over the teeth. Anyway it runs like complete garbage now and has codes for the cam phasers. I have some more research to do, but i'm pretty sure i need to pull the valve cover and retime the engine now.

Turbo shaft play was fine.

Then came borescoping the cylinders. The pistons have erosion from detonation on the exhast side. They are increasingly bad as you can toward the back of the engine which is probably because the rear of the engine runs hotter.

My guess is this dammage is old and from running low octane gas. I remember the couple we bought the car from saying that it was fine to run 89 in it and you didnt have to pay for premium. Which i verified to be true per the manual. Its 89min and 91 reccomended. Figured it wasnt a big deal since its a modern engine with knock sensors and so on. Perhaps someone before that ran 87. I recall from records they werent having the oil changes done at the dealer so there could have been non LL01 oil in there for awhile. LSPI?

pics attached. I am not sure i have 2 and 3 in the right order in these.

For next steps, I need to get it running again. Really frustrating that i have to open the engine up over a test i didnt even need to do.

Long term, I'm not sure. I have no apitite to rebuild this engine. Before this whole ordeal it ran perfect. Had i never sent the sample in, i'd be living in blissful ignorance. My big question is will this lead to a suddent catastrophic failure or will this thing just eventually start consuming large amounts of oil. Which funny enough it consumes nearly none now. Just how much of a problem is this... Perhaps this isnt a 300k motor anymore, but id sure be happy to limp it along for another 50.

piston 1.jpg.webp


piston 2.jpg.webp


piston 3.jpg.webp


piston 4.jpg.webp
 
I think yours may be the first internet documentation of N20 detonation on a stock engine. It might have had a bad tune somewhere in its past. I am sorry you had to find this. I don’t think anyone can realistically tell you how long it will last without intervention. Was there bore scoring as well? Going to beat a dead horse: but you said the timing chain passed the test, were guides and slack all ok also?
 
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other question i suppose is if this detonation is still happening. Could be a knock sensor issue or something.

If this detonation damage is old, its approaching being over 34k miles old... which I think bodes well for it having life left.

guides looked ok on the borescope. Slack is checked with the elongation test tool and that passed. I'll have the valve cover off soon here to get everything functional again so ill get better look then.

I wasnt able to look at the bores for scratches with my depstech camera. anyone have recommendations? something articulating seems critical.
 
I’m no expert on anything, but that erosion looks like detonation from a lean condition, not necessarily LSPI. I think if you research LSPI telltales you will find that that’s not what it looks like. It looks like that engine went lean under boost at some point. It doesn’t take long for it to look like that. And it might’ve happened many tens of thousands of miles ago as you stated.
 
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I’m no expert on anything, but that erosion looks like detonation from a lean condition, not necessarily LSPI. I think if you research LSPI telltales you will find that that’s not what it looks like. It looks like that engine went lean under boost at some point. It doesn’t take long for it to look like that. And it might’ve happened many tens of thousands of miles ago as you stated.
Definitely not LSPI. N20 stock engine does not have those issues.
Who knows what it could be.
 
I’m no expert on anything, but that erosion looks like detonation from a lean condition, not necessarily LSPI. I think if you research LSPI telltales you will find that that’s not what it looks like. It looks like that engine went lean under boost at some point.
That's what I'm thinking as well. A vacuum leak would tend to cause a lean condition. Even if the fuel trims are properly adjusting for it, ignition timing would be more advanced due to the low MAF sensor reading, which can cause detonation.

@levesqu6
Maybe monitor for knock with your scanner if it has that capability, to see if the detonation is still an issue. If the engine has a wideband O2, monitor the AFR at high engine loads to see if it's normal. If you've got knock, and fuel trims are still a bit positive, consider cleaning or replacing the MAF sensor.

Other than that, I would just motor on and then do another UOA. You may have fixed the problem already if it was a vaccum leak.

 
This isn't LSPI. Looks like standard detonation (after spark issue) from running fuel without the proper octane rating for a long period. Pre-ignition issues (before spark) are typically much more damaging due to higher cylinder pressure vs. detonation (ping/knock) which occurs after spark.
 
When i was looking at fuel trims the lambda seemed to make sense. Around 1 for light loads and then richening up with higher loads. Seemed similar to when i played with scanner with the n63. Good thought on checking higher loads and doing some logs, should see short term fuel trim be close to zero if MAF and wide band agree. They probably arent both bad. I know from earlier experiments that fuel trims are zero on the freeway but that obviously isnt heavy loads. I did find that if i plug into the car with ISTA on a laptop there are by cylinder knock channels. Another easyish thing to do. Unfortunately ISTA has no logging capability, just read outs.


I'm still mentally getting over needing to re-time the friggin engine.
 
Not sure what to make of the wear metals but from looking around the forum this is not normal for this engine. At 12.8 iron per 1kmile this is just under the 14.1 i saw for someone breaking in a n20 after a engine replacement.

I spent sometime tonight looking at the intake path and filter. Filter is a Hingst (OEM) and the box filter, and intake path all look to be in good shape except the pipe that brings the PCV to the turbo inlet pipe. It was only clipped on one of two sides and is all oily in the area. It didnt look dirty inside the tubes and it doesnt seem like it would have been leaking much air but it certainly was leaking some. No codes for MAF air flow being unbalanced or anything like that. The inlet pipe to the turbo has some oil residue on it but i think that is coming from elsewhere.

I havent been in this engine since 127k to do the vacuum pump and I did the turbo at 119k because of the wastegate.

This engine is one of the vintages with the infamous timing chain issue. It does not appear to have ever been replaced on this vehicle. There is no evidence that it is a current problem either. Since the chain is essentially wrapped in plastic guides, something related to it wouldnt show up as high aluminum too.

Oil filter looked great when i looked in the pleats. Mann filter used. Oil change before this would have been castrol 5w40

View attachment 249788
Dunno, but I always use Oem oil and air filters. Silicon does not look bad.
 
I feel your pain. I have mis-timed a few MC engines when adjusting shim under buckets. Turns a profitable job into a loser instantly.

All this new knowledge of your situation and I wonder even more where the present iron came from, especially since the detonation events were likely in the distant past.
 
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