My 97 318i (192,000 miles) is losing power and mileage is very low, it started gradually but is getting worse and is now almost to the point of it not driveable. It seems to have decent power at low RPMs but has less and less power as the RPMs increase. I've replaced the fuel filter, spark plugs and air filter but that made no difference. The car starts normally and idles fine. I'm beginning to think it may be the catalytic converter.
Loss of power and fuel mileage. on 1997 BMW 318i
by Mississippian in Moss Point, MS on September 14, 2010
3 answers 1 comment
ANSWER by dandd , September 14, 2010
Yes, it could very well be a defective Catalytic Converter. If you have a Check Engine Light or Service Engine Soon Light on, then you may have a code P0420 -> which indicates a defective Catalytic Converter. I would also do a fuel pressure test, just to make sure that the fuel pressure is adequate. Also, if you have other codes, then by all means trace those down as well.
COMMENT by Mississippian , September 30, 2010
Catalytic converter was the problem, ordered bolt on OEM replacement and power is fully restored.
ANSWER by Visitor , January 22, 2011
it is definitley the cat converter had to replace mine and now it runs like the day Ibought it. P.S. hope you didn't sell it.
ANSWER by mensa man , September 27, 2010
idle control valve and pcv valve replace.