Hunting of the 1990 BMW 525i engine?

I have a 1990,BMW 525 i.When car is idling the the rpm meter shows around 720 rpm.Once is two or three mins the rpm drops to 500 rpm for a second and comes back to 720 rpm.Is it normal?or i need to check with injectors and sparkplug.I used STPp fuel injector cleaning additive to my fuel now.Please advice me.

Expecting your valuable replies

Hunting of the 1990 BMW 525i engine?adware

u will probably find that your are drawing air from somwhere check all breather on the inlet manifold .another way to check is to start enigine and spray light oil like wd40 arund inlet manifold and listen for changes in the engine iff it is sucking frome there the light oil will be drawn to the point where the leak might be.

Hunting of the 1990 BMW 525i engine?antivirus scan

try ebay
It could be anything. At this age, I would not be concerned. BMW's tend to have an uneven idle anyway. It's part of their personality and as long as it doesn't stall, save your money and enjoy the ride.
Have you got air con if so this is normal ?
thats not a bad thing the car is getting old a simple tune up will fix that kinda thing !