Engine failure

[MartinS]

Sorry to have to post again so soon, was test driving to day collecting a log file to fine tune AFR with new VVT cam angle table and engine suddenly failed.  

I was travelling in 4th gear at approx 2600 RPM and went to downshift to 3rd to collect date at higher RPM.  The engine stalled when clutch pedal depressed but restarted immediately on letting clutch out.  At this time, the Trig1 error counter reports 1 error.  The engine continued to run well subjectively.

The engine runs for around another minute at about 3600 RPM at which point the recorded RPM jumps to 14,000 RPM (engine did not surge, just died, no identifiable engine sounds or surging etc), Trig1 error counter jumps to 4, LH inlet pos error counter jumps to 4, and RH inlet trigger counter records 1 error at which point the engine is not running (but no apparent mechanical issue, just the sound of an engine on overrun with no combustion occurring).

The only other thing I can see unusual on the log is that about 30 sec prior to the engine failure (about 30 sec after the stall between 4th and 3rd downshift), the LH cam position sensor starts showing the LH cam running about 10 deg less advance than the RH until failure (they are essentially the same previous to this).

Here is the Log file.

https://drive.google.com/file/d/1S03bEa8IqB5e0Zy4Qet-zJrnul35z7BZ/view?usp=sharing

Any insight greatly appreciated.

Sorry, should read downshifted to collect data at higher RPM

[MartinS]

ok, just went out to see if engine would re-start cool.  Cranked with starter, crankshaft turned maybe a turn or two, clunk, stopped turning.  

I've heard this before when a friends interference engine snapped a timing belt.  I replaced the chain tensioners and inspected everything but, unless someone has a better explanation, working diagnosis is slipped or broken timing chain.  Or maybe an individual valve problem. 

Is that consistent with the log file?  

I'll have a closer look tomorrow or the next day and see if I can confirm.  Whatever it is, I was thinking it was electrical until it locked up this evening.  Strange presentation given it spun freely on the over-run after it quit and I actually tried to re-start it (seemed to spin freely on starter motor), then used the starter motor in first gear to roll a little further of the highway.

Meant to say: replaced the chain tensioners and inspected everything about 4,000 km ago

 

[Adamw]

I assume it was stock camshafts right?  With aftermarket cams you can potentially have valves clash when moving VVT but that generally is impossible with stock cam that are timed correctly.  Otherwise yes it sounds like a cambelt is damaged or slipped.  

The log file share isnt accessible, try right clicking on it and chose sharing then check it is set to "anyone with link" or similar.  

 

 

[MartinS]

Sorry, thought I'd clicked on 'anyone with link' but it still said 'restricted'

This should work: https://drive.google.com/file/d/1S03bEa8IqB5e0Zy4Qet-zJrnul35z7BZ/view?usp=sharing

[MartinS]

Took timing cover off, timing chains all in good condition, tensioners in place and working, valve timing marks all pointing in same direction suggesting there's nothing wrong with the timing.  Can't turn the engine to go to #1 at TDC but 95% sure the timing is ok.

Which leaves me with the question: why did the engine turn over freely then jam when I cranked it last night when the engine was cool then jam suddenly?  Oil at lower end of marks but enough, VVT was working just before failure so there was oil pressure.  Cannot turn engine with a socket on the crank bolt (either direction which suggests not piston against valve). 

At a loss, will keep investigating tomorrow.

[dx4picco]

Valve drop?

[Adamw]

The RH inlet VVT that is above target looks like possibly a faulty AVCS actuator.  You can see the solenoid duty cycle is down at 30% sitting on the minimum clamp but the cam is only returning very slowly, it should move almost instantly with only 30%DC - you can see the other side rarely drops blow about 45%.  

I notice at the end just after the RPM spike the RH cam position falls to zero whereas the LH is still sitting on target until the RPM drops below the lockout.  The status still shows active and the error counter is not increasing so that seems like something to do with the RH cam has failed.

[MartinS]

2 hours ago, dx4picco said:

Valve drop?

I would say yes but the engine is locked in both directions.  Anything where the valve is dropped or the timing is off or timing chain broken, I would expect the engine still to be able to turn backwards.  i.e. the engine is jammed against the valve but you should be able to turn backwards a little and pull the piston away from the valve.

Ok, I noticed this morning there is a significant oil leak somewhere around the RH intake valve sensor or could be the actuator.  There's oil on the top of the RH head where the injectors are but I can't tell if it's from the actuator at the front of the engine or the sensor at the back.  The whole deck is damp with oil which is dripping down at the front of the engine.  Although it could be the RH exh pos sensor but I think it's from above that.  Strikes me not a coincidence.

Not sure I'm on the same page but the RH cam actuator is actually new.  Could a failed pos sensor cause the engine to fail?  

I'm not sure why the engine is jammed.  Almost like it's a separate problem but it's just too coincidental.  Might have to pull the trans and see if something's jammed in the flywheel.  I just can't think this is two separate issues but I can't think of one issue which will cause these problems...

To clarify, I'm calling the front of the engine the front as it would be in a Tribeca ie where the timing chain cover is.  The engine is reversed of course because it's in a Vanagon so the RH of the engine is actually on the driver's side of the van.  I'm orienting the issues so the LH engine is pass side van and RH engine is driver's side.  This is how the ECU is oriented in terms of timing.

Another thing I don't understand: I just put about 4-5,000 km on the van with no VVT.  Intake and exhaust actuators at baseline.  If the RH cam actuator failed, the cam would return to baseline where the engine should run just fine.  I'm not understanding something here...

[Adamw]

48 minutes ago, MartinS said:

If the RH cam actuator failed, the cam would return to baseline where the engine should run just fine.

Correct the actuators have mechanical stops in a "safe position" so even if fully advanced or fully retarded the valves shouldnt hit anything.  

My thoughts were more along the lines of possibly something like a drive pin or keyway between the cam and actuator sheared, so the cam is no longer doing exactly what the actuator is.  But really it is all speculation at this point, you wont know until you start pulling some bits off - and sometimes even then there is not always a clear answer to the root cause.  

[MartinS]

Any clue in the fact the crank pos sensor spikes to 14,000 RPM?  What explains that?

Presumably, that's when the event happens which causes the engine failure.  What stumps me is why the engine keeps spinning freely (including attempts to re-start) until it jams much later.  What has caused an apparent crank jam and what is the common event which could cause all of this?  I'm not sure whether to start pulling things apart (and if so where to start) or buy another used engine...

 

[MartinS]

Contents of sump, oil pump seized, crank seized.  Something failed catastrophically.

https://drive.google.com/file/d/1ud_8OUhbArc3gVnq6RUmLS0dRZDFCANs/view?usp=sharing

[MartinS]

First pic is left bank cam actuator cylinder (ie cam actuator removed), note metal disc at base:

https://drive.google.com/file/d/1vtveQA7leN-xTleP0mTAtcTt4JkbQQ49/view?usp=sharing

This is the right bank actuator cylinder.  Actuator looks fine, note that part of the metal disc at the base of the cylinder is missing with a clear break in the metal. 

https://drive.google.com/file/d/19W3XrsGUb4kgUObtAzZYFiL5Iiwes88p/view?usp=sharing

Have looked more closely at engine, #1 Cylinder connecting rod broken, one of the #1 exhaust valve stems broken, the other bent, spark plug tip smashed.

Looks like that disc broke at the bottom of the RH actuator cylinder and the piece of metal somehow jammed the #1 con rod which broke throwing the piston into the open exhaust valves.  The oil leak I noted previously was a minor unrelated issue (o-ring on cam angle sensor Rt intake).  On visual inspection, RH intake cam appears healthy, broken piece not having affected it. 

Online search and I can't find any other descriptions of a similar issue.  I'm going to assume it's a one in a million piece of bad luck.  80,000 Km JDM EZ36 on it's way.  Should be back up and running next weekend!