1997 E39 rough cold starts and loud air pump - BMW Forum

Sugarmel · 07-16-2008, 01:44 PM

My car runs rough (like it is missing) on cold starts, and the secondary air pump sounds loud. After about two cold starts, the check engine light comes on. The fault code is "F0" which is "Misfire detected on cyclinder 3". I have swapped out coils, and plugs with other cylinders, but I keep getting the problem with cylinder 3. After a few minutes of the cold start, the idling smooths out, and the pump gets quieter before the pump eventually shuts off. I have changed the valve for the air pump also. Any ideas as to what I shouls check next? Thanks.

darkhorse737 · 07-16-2008, 04:25 PM

have u changed your air pump filter lately? :-?

Sugarmel · 07-16-2008, 10:23 PM

No, I haven't. Will try that and get back my findings.

prmoorman1 · 07-16-2008, 10:24 PM

Darkhorse, where is the air pump filter located, and what does it look like?
My 97 528i seem to make a similar noise, like an exhaust leak upon start up.

darkhorse737 · 07-16-2008, 10:56 PM

Right hand side, front of wheel well, sir... ;-)

prmoorman1 · 07-17-2008, 08:18 AM

Can ya actually just replace the filter,or do one have to replace the pump.
Again,what is the sign that sez,to change the filter,or replace the pump?
Thanx Darkhorse!!! It is good to know these things,I have only been a
beamer owner since Dec.

LOS · 07-17-2008, 08:42 AM

Sugarmel, it could also be your MAF sensor...

LOS

darkhorse737 · 07-17-2008, 09:03 AM

Quote:

Originally Posted by prmoorman1

Can ya actually just replace the filter,or do one have to replace the pump.
Again,what is the sign that sez,to change the filter,or replace the pump?
Thanx Darkhorse!!! It is good to know these things,I have only been a
beamer owner since Dec.

look carefully at the top of the air pump. You might see a cover that you can pry or twist to expose the filter.

If in doubt, call your local dealer and request for them to fax you an exploded view of the air pump assembly. and it will show ;-) they do not charge for that service.

darkhorse737 · 07-17-2008, 09:06 AM

SugarMel, i forgot to ask... did u ever get a compression reading on your #3 cylinder? If yes, what was the pressure please?

Sugarmel · 07-19-2008, 12:50 PM

I have not had a compression reading. I will look into getting one done. Also, I do not get any error code for the MAF meter.