89 320 Oil Leak and Missing

[Ciaran Moynihan <ciaran.moynihan@xxxxxxxxxxxxxxxx>]

Hi All

I have an 89 320i (M20 engine v similar to the 325s etc I think)

Anyway I had a problem recently where the idle was erratic (Hunting) and the
engine sounded like it was misfireing at higher revs ( most noticeable at
about 2500 rpm ).

As the car needed a service anyway. I changed plugs, oil, oilfilter, and air
filter. Problem got slightly worse !

I checked out the ignition - and replaced the distriutor cap and rotor as
the contacts were badly pitted. The resistance values for the plug leads
check out OK also according to the specs in Bentley. No real difference to
drivabliity though. 

I then suspected an intake air leak or clogged injectors. I ran a couple of
doses of Redex fuel injection cleaner through it and removed the injectors
for visual inspection. The nozels of the injectors were pretty badly fouled
with crud so I cleaned these up a bit and refitted. The Injector O-rings
looked perfect no sign of any damage at all.

I replaced the inlet manifold gasket and in the process I found a crack in
the breather pipe that runs between the throttle body and the rocker (valve)
cover. This guy cought me out before as it tends to perish on the underside
and is very difficuly to spot until it is removed!.  I repaired this and
engine idles better now (not perfect yet though). There is also still a
slight miss at higher revs.

In the process of replacing the inlet manifold gasket I had alot of
difficulty in reseating the oil breather pipe that runs from the oil pan to
the inlet manifold. This is a spring loaded rigid tube approx 10 inches in
length and 3/4 inches diameter. This developed a serious oil leak at the
oilpan end. I have had this pipe out a number of times before and never had
a problem like this. I dont recall there being any specific seal at this
joint except for a small O-ring set into the opening in the oil pan. I have
checked Bentley but it doesnt seem to give much info on this joint (
probably because it doesn't cause any problems in general ;-)  

Can anyone tell me what kind of a seal is supposed to be here ? I have fixed
it temporarily using instant gasket sealant however I am still losing a
small amount of oil. Should I just get an O-ring of the correct size and
stick it on  the end of the tube ? Has anyone else had problems with this
pipe ?

One thing that worries me is I have noticed with other cars that if the
piston rings are worn then oil can get blown out through every oriface
possible although as there is only 120K (miles) on mine then this is
unlikely - or is it?

As for the Original problem with the misfiring - I now suspect that its down
to one or two things

a) either the valve clearances are too tight or I have a bent valve - Are
bent valves a common problem on the M20 engine ?

b) The Air flow meter is faulty. I have checked this using a multimeter and
the values I got seemed to be prety inconsistant and non linear however
Bently does not actually give start and end expected resistance values for
the airflow meter. Does any one have these values for motronic 1.1 in a 2L
M20 ? I am reluctant to suspect the airflow meter however as if it was as
faulty as the non linear readings would suggest then I dont know how the car
is running at all?

Any thoughts out there ?

rgds

Ciaran Moynihan

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