1990 525i few problems

the car has a real rough idle.
also its only getting like 15.9 mpg is that normal?
and then also when its idling the check engine light is on but once you hit the gas it goes off.

ohh and im getting an error brake light circuit. what does htat mean?

thanks
jay

cant help you with the lights but with rough idle it could be from spark plugs, dirty air filter, the mpg is usuallu low on BMW's because they consume alot of fuel, but you also get alot of power, so thats one thing you have to get used to, if you buy a K&N air filter it helps the mpg

I found with my 1992 (M50) that if you inspect/trim all of your vacume lines... and use electric contact cleaner on all the sensors... and spray carburator cleaner in the throttle body and the MAF sensor screan -- you should get a noticable increase in MPG.... Don't forget to use fuel injector cleaner and put a bottle of octane increaser in one of your tank (after you use the fuel injector cleaner) and that too will clean the inside of your engine.

Here's another tip, if your car is an automatic, I found that cleaning the gear selector lever has a positive affect on performance and MPG, but the most noticable improvement in MPG may also come from servicing your auto transmission -- and making sure you have the proper fluid level.

My 1992 BMW 525 wagon gets 14 city (which is characteristically poor) and 24-26 MPG on the highway. Also I use regular fuel and have noticed no improvement in performance or MPG using premium.