Engine running rough and shaking badly at idle and at higher rpm too, hot /cold

[Dave M]

Just in case, make sure cyl #6 is not 'fuel washed'. Either pull the plug and wait a long while and/or pull the fuel pump relay and turn it over a bunch.

If you get compression back, take a very good look at your plug ceramics as I had similar symptoms and it was a cracked ceramic. I concentrated too much on the business end of the plug and not enough on the boring end. If you want to find a bad cylinder/plug on the M50, try pulling the wire harness from each coil pack listenng for no change in idle. Bentley/forum members probably don't recommend this method, but its worked for me on more than one occasion (just like pulling the plug boot on a single coil ignition system).

Good luck with it, hope it not a serious problem,

Dave

[alex 1993 525i auto]

Thanks all for the infos, here is an update, but the job is not finished yet...

So 1.5 months ago, I had a problem with my car and now I'm in the process of removing the cyl. head to get the valve job done in a machine shop. It is in storage for the winter so I do it myself during weekend when I have time to work on it.

I tried this to test if it is the exhaust valves that are stuck open or broken: I have an issue on the cyl. 6. with no compression at all. After removing the cyl. head cover and fan clutch, I turned the engine to see the cams and hydraulic cam followers and they looked fine. Then I set piston #6 at the highest position with cam lobes pointing up, which close the valves. I added injector cleaner liquid in the spark plug hole with a funnel and I saw the liquid free flowing down. I did the same test with cyl. no. 2 and the liquid was staying inside for a few minutes. I heard the liquid going down the exhaust when pourring it in the cyl. 6. When I remove the intake manifold there was no injector cleaner in there, only a little bit of oil.

Next step will be to remove the exhaust manifold, set the engine at tdc, remove the vanos then cyl. head. and bring it to a shop for the valve job and get the head cleaned. I know I have to buy the gasket set, head bolt set, exhaust manifold bolts and nuts etc. I heard/read that exhaust manifold nuts are very tough to remove, I'll see how hard it is soon. If anyone has tricks and infos please let me know! Thanks

[rockin1978TA]

My 535 was running like that, tracked down a small leak at the intake to head. Used some permatex copper to plug the leak, runs great now.

[alex 1993 525i auto]

Hey! I realized I hadn't followed-up on this one. When removing the exhaust manifold it was an easy find, cyl. 6 exhaust valve had a small hole on the outer side of the valve... for sure this cylinder couldn't have compression... I removed the head, brought it to a machine shop ($500 to get the head refurbished, not bad I tought). Another $400 of gasket set and various other parts and that was it. It took me kind of 40h job alltogether (+ reading time and shoping time) for a first timer, and the car started fine right after reassembly. Thanks to all who post in forums good tricks of all kind (and to the Bentley manual and also I found the Pelican tech info center very useful). The car has been running fine since that repair 2 years ago but just started a little something I'm into checking:

http://www.bimmernut.com/forum/5-ser...00-rpm-so.html