Crossthreaded plug

[kastigeer]

I got a second hand 3 litre e34 (1994) that when it came around to servicing I found that plug 8 (I think it's 8 anyway - right side at the back) has had a collar hammered down over it to keep the plug in - the only reason I can think of doing this is if the plug was crossthreaded at some point. The car has now started misfiring, so I've got to do something about it - I've got no comeback to anyone, so I gotta sort this one out myself...

Despite the obvious problem of getting the plug out (there no bloody room to maneouver on that cylinder), and what to do once I get it out, my question doesn't related to this.

I've had a friend who's a senior tech with Audi have a look and he says that it's misfiring to badly for it to just be one cylinder on a V8 in his opinion, so:

a) Either there's something else wrong and although the plug is still wedged in tight it may not be the cause of the misfiring problem.

b) The plug is at fault and the engine management is firing the plugs in pairs and has shut down two because of a problem on cylinder 8 (or something like that)

I'm going to try and get it onto genuine BMW diagnostic kit to see if that sheds any light, but until I can my question is whether option b) above is a possibility?

Can anyone help our on this one - I don't have much hair left, and it's going to vanish rapidly when the costs of fixing this one mount up (especially if I take the head off to sort the plug out only to find it's not the plug at fault ...)

thanks
Barry

[Derek A.]

You could be up against a Nikasil engine problem. From my understanding when these engines start to run rough it could be as a result of the engine clock degradation problem. You might want to try a helicoil, but it could be very difficult to do with the cylinder head on the car. I would reccomend that you do a leakdown test on the cylinders you can get to, this might help rule out an engine block problem.