I have a 1995 525i with the m50 6 cyl, after driving for 20 min I was sitting in traffic and my engine shuttered and had a slight hickup, the problem became gradually worse and then the Idle and acceleration just plain sucked, it now idles and accelerates like a 3 cylinder. I checked it again in the AM and it's still the same, She has performed flawlessly prior to that, what could make it come on slowly like that, vacum, fuel, air, It has me stumped..... any help would be great, the car has always been serviced at the dealer and onlt has 139,000.. Thanks in advance for any help....
Vince

Pull your plugs, what do they look like?
Test your spark
Test fuel pressure
Test vacuum

Also, run the car then take off the oil cap or the dipstick, does it run the same? If so then you probably hve a vacuum leak as there is supposed to be vacuum, when you take that off its opening up the vacuum lines therefor making it run like shit. If when you take off the oil cap it runs the same*shitty* then you may have a vacuum leak somewhere, then its just a matter of tracing it.

spark plugs

The plugs are 1 month old, I pulled the oil filler cap and it still runs shitty, I quess I will start looking for a vac leak, I noticed the intake boot between the mass sensor and throttle body is dry rotted and cracked. thanks for the input, I plan on checking the other items too.

The plugs are 1 month old, I pulled the oil filler cap and it still runs shitty, I quess I will start looking for a vac leak, I noticed the intake boot between the mass sensor and throttle body is dry rotted and cracked. thanks for the input, I plan on checking the other items too.

Replace/Use osmeone elses and see if that fixes it, if its cracked air is getting in and might be screwing stuff up!

I replaced the mass air boot, breather vacuum lines and o-ring, tested the mass air sensor(checked ok) then checked the throttle position sensor and it checked ok,then checked the idle speed valve and found that the ohms were off from what the manual lists, I started the car and It seem better untill I put on the A/C, then it goes to hell again, Would this be because of the Idle speed sensor valve? or oxygen sensor? or both.....

Update.. I have replaced the Idle control valve and most every vacuum line and plastic fitting I could locate and nothing has improved performance, still no codes and I have a sulfer smell from exhaust. I guess I will go after the fuel injection....

UREAKA...... Well I found the ILL culprit, seems when the spark plugs were changed come one was cleaning the plug galley with a wire brush, somehow a metal brisel found its way into the spark boot on the coil, after removal .....ALL WAS WELL....Thanks too all of you for your help on this, Keep em running.....