Bad News : Engine Knock

[m3f_buckley]

Hey guys,



I hope everyone is having a great New Year! I am hoping that the community can help me diagnose (or help me start) a problem with my 98 M.



It is a pretty cold winter here in CO and I drive my M daily. A few recent mornings I have turned the engine on to hear a constant knocking from what sounds like the block (rod knock would suck). I noticed that this is not an rpm dependent knock (although it only seems to happen when idling) and I believe that it 'may' be temperature dependent but I couldn't be quite sure because of how cold it has been.



This morning, I went out to check the CELs and do some basic diagnosing. I turned the engine on the first time (~28deg) and a constant knocking sound appeared with what seemed like a misfire until I revved above ~1000 rpm. I turned the engine off, went inside for an hour or so (engine did not warm up - only had it on for 2 minutes) and came back out. I started it and the engine ran (and idled) normally with zero noticeable problems. This seems to be an intermittent issue..



FYI, it didn't seem to have any problems after the car warmed up until last night when it knocked and misfired constantly on the way home from a movie.



Here are my CELs and readings from the Peake R5 FCX3



CELS:



P0301

P1250

P1189

P0430



Peake Codes:



EE - Misfire - Cylinder #1

F1 - Misfire - Cylinder #4

F2 - Misfire - Cylinder #5

EA - Catalytic efficiency below threshold (cyl #4-6)

E3 - O2 Sensor adaptation limit (Cyl #1-3)

E4 - O2 Sensor adaptation limit (cyl #4-6)

E6 - Pre-cat O2 Sensor switching time (cyl #4-6)

dE - Time to closed loop temp too long





If anybody has any suggestions regarding where to start, please let me know.



Thank you,

Adrian

[m3f_englishtom1596q]

rod knock would be rpm dependent so i think your issues lay elsewhere. i would get it up in the air and have someone start it while you listen.

[m3f_m3onrails]

You would know if it were rod knock, its crazy loud and RPM dependent. I know from experience, its NOT something you want to ever hear.


Have you checked your spark plugs? sometimes they can knock if they're not tightened all the way.

[m3f_hencini]

Originally Posted by m3onrails:

Have you checked your spark plugs? sometimes they can knock if they're not tightened all the way.



That was my initial thought, but I can't imagine a loose plug throwing all those codes. :-)


Plus the spark plug noise is RPM dependent.

[m3f_buckley]

I am aware that rod knock is rpm dependent (I've heard it on many occasions with my race car). I am not saying that this particular sound IS rod knock, although, until it disappears, it sounds very similar. I will check compression, look at the spark plugs, and try to track down the noise. Hopefully it isn't a busted valve spring like last time this car went down. I have a feeling it may be something in the head. I will report back.



Thanks,

Adrian

[m3f_buckley]

I have yet to do a compression test but I drove the vehicle to work today (upon startup there was no knocking). I arrived at work, went to lunch, and it happened again. Threw the following CELs.



P0301

P1250



I do not have my Peake tool currently but will report when I get home. Please advise (and subscribe if you have already provided advise).

[m3f_buckley]

Well, I figured it out. This may be good news and it may be bad news but here is the news...



The crank pulley came loose. The crank bolt is less than hand tight.



This brings up a few questions...



1. Does this engine have a woodruff key?

2. Can I torque this bad boy down and be happy?

3. Any further suggestions?



Thanks,

Adrian

[m3f_m3onrails]

Yes the S52 has a woodruff key. What you'll have to do next is confirm whether or not the woodruff key stripped or if the bolt is really just lose. The problem is that the bolt should be torqued down to ~300ft/lbs IIRC, so you'll have to find a torque wrench that goes that high. I've also heard (not confirmed) that the 'jesus' bolt is TTY, and I just bought a new one when I was building my engine just in case. You might want to confirm that the bolt is TTY, and confirm the actual torque numbers (listed in the TIS), but I hope this helps a little.

[m3f_///Momentun]

Originally Posted by buckley:

Well, I figured it out. This may be good news and it may be bad news but here is the news...



The crank pulley came loose. The crank bolt is less than hand tight.



This brings up a few questions...



1. Does this engine have a woodruff key?

2. Can I torque this bad boy down and be happy?

3. Any further suggestions?



Thanks,

Adrian

Is the bolt broken or stripped? Just make sure the threads in the crank are not ruined.

[m3f_buckley]

Well, I torqued it down. The crank pulley has about 10 degrees of movement. I hope that the woodruff key in the crank is okay. I got lucky this time.. Now there is a severe misfire that I need to track down. Thanks to everyone for the help.