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-   -   93 525i M-50 vanos misfire (http://www.bimmerfest.com/forums/showthread.php?t=647823)

Xerxes 09-24-2012 10:18 AM

93 525i M-50 vanos misfire
 
I took the car to a track day and drove it pretty hard for about 15 minutes straight. When I pulled off the track the car has a misfire. I'm going to switch the coil packs (as I have a spare set) and see if I just cooked one, but if that's not it I thought I'd see if anyone else has had a continuos misfire and what the cause was.
I also missed a shift (3rd to 2nd instead of 3rd to 4th) and did briefly over-rev the engine.
Any insight would help.

BMR_LVR 09-24-2012 10:39 AM

I think you are on the right track (pun intended :D)

Xerxes 09-24-2012 02:20 PM

Not a bad coil, I'm thinking maybe a fuel injector or plug.

BMR_LVR 09-24-2012 03:05 PM

I agree that those are good to look at next. If that doesn't point you to the problem, consider a compression check to see if you burnt a valve, broke a ring or something like that.

Good luck and keep us posted.

Xerxes 09-25-2012 07:20 PM

Well I floated the valves when I missed the shift, not badly (a relative term), so I'm taking the head off and then I'll know if I need new pistons or not. Depending on what how bad it is I'll either rebuild the head and polish the piston crowns or pull the whole thing and put my spare motor in.
I'm hopeing just the head and light polish since I don't have a garage at the moment and I'm running out of nice weather, since the spare engine is still in the donor car (a rear ended 95 325i) for my e21 323i m-50 conversion.

BMR_LVR 09-25-2012 07:24 PM

Well, you're way above my ability there. Congrats on having the cajones to do it. I kinda thought you may have floated a valve or three with the over-rev, but I wasn't sure about it. Good luck and let us know how it goes and what you find.

Oh yeah, pics are MANDATORY :D

robertobaggio20 09-27-2012 02:06 AM

Quote:

Originally Posted by Xerxes (Post 7096466)
Well I floated the valves when I missed the shift, not badly (a relative term), so I'm taking the head off and then I'll know if I need new pistons or not. Depending on what how bad it is I'll either rebuild the head and polish the piston crowns or pull the whole thing and put my spare motor in.
I'm hopeing just the head and light polish since I don't have a garage at the moment and I'm running out of nice weather, since the spare engine is still in the donor car (a rear ended 95 325i) for my e21 323i m-50 conversion.

Have you ever grooved a cylinder head?

_Ethrty-Andy_ 09-27-2012 03:01 AM

STOP

diagnose the problem first. This car has built in diagnosics, so scan it. It will tell you if its a dead coil, or dodgy injector. it will also throw the coil error code if the spark plug is dead.

if no error codes come up first, then start looking at mechanical possibilities as opposed to electrical ones.

Xerxes 09-27-2012 04:00 PM

I have not grooved the cylinder wall before, I had a 67 VW fastback with an AP race case, Berg counterbalanced crank, oversize jugs, etc, etc, and sucked a valve while drag racing (20 years ago), I heard it before I felt it and shut it down, it left 3 crescent shaped indentations in the piston crown but no pieces broke off and scored the cylinder wall.
I have checked for codes and didn't get any, I haven't done a compression test as someone made off with one of my tool chests and I don't have that equipment at the moment. I know the pressure gauge to do this isn't that expensive but I find it hard to buy the same tool twice when I rarely used the first one, but before I tear it apart I'll scope the combustion chamber and see if I can see any damage, that will also let me know if I should just swap it with the other m-50 engine I have or if a top end re-build is all that's required.

robertobaggio20 09-27-2012 08:38 PM

I meant grooving the cylinder head, around the valves. Have you heard of the somender groove? Please check this out on google and youtube, some really interesting writeups about it out there.

Xerxes 09-27-2012 10:35 PM

I hadn't heard of it, the last few years I've been working on 4x4's and nobody had mentioned this particular modification. It seems similar to "rifling" your intake ports or the intake valves that have spiral ridges on the back. This may have the advantage of not slowing intake velocity to achieve better mixing in the combustion chamber.

Xerxes 09-29-2012 09:42 PM

I don't know if I can put the Somender groove on a BMW head, the groove requires a "squish" pad and BMW's (to the best of my knowledge) don't have that. I might put McFarland dimples in the head but let's see what I have when I take it apart. I haven't disassembled an m50 before so I'm reading up on it first, there are some good tech journals at Pelican auto parts, though I'm considering making my own tool to remove the cams instead of the somewhat dodgy "no special tool required" procedure. I'll have to get a better picture of the tool first and then figure out it's dimensions once the head is out of the car.

robertobaggio20 09-29-2012 11:37 PM

This is an interesting article on Mcfarlane dimples :

http://www.popularhotrodding.com/tec...ontiac_engine/

This is an interesting forum thread on Somendar grooving :

http://forums.turbobricks.com/showth...=66779&page=37

I don't think that m50s have much of a squish plate, but there is a little space on around the valves for grooving. It looks too small though but I've not studied it up close and personal.

Check this out :

http://www.youtube.com/watch?v=5YbcO...layer_embedded

Xerxes 11-04-2012 02:21 PM

Well, I'm finally able to move both cars to their new home, a friends garage, where I will do the engine swap so the 525i will be back on the road. This way I'll have the car back and I can take my time rebuilding the engine that will eventually end up in my 81 323i. I of course will have to see what other performance mods are out there since I'll have it torn down anyway. I have been looking into the "grooves" as we'll as the McFarland dimples, I think I will use one or both to some degree on the head, but I need to look at the head first and see what there is room for.

robertobaggio20 11-04-2012 04:46 PM

Quote:

Originally Posted by Xerxes (Post 7175297)
Well, I'm finally able to move both cars to their new home, a friends garage, where I will do the engine swap so the 525i will be back on the road. This way I'll have the car back and I can take my time rebuilding the engine that will eventually end up in my 81 323i. I of course will have to see what other performance mods are out there since I'll have it torn down anyway. I have been looking into the "grooves" as we'll as the McFarland dimples, I think I will use one or both to some degree on the head, but I need to look at the head first and see what there is room for.

Pictures sir pictures ! This is critical. Your experience will pave the way. If you can oblige us :)


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