very annoying surge problem. '86 325es

[elzo]

Ok people, here's a tough one. My brother bought this car(1986 325es) back in 1994 with about 50Kmi. Several weeks later we noticed that it had some kind of weird surge; at idle or on the go. We are mechanically inclined and have solved some tough driveability problems before, but this one is not budging. Well the problem is still there now, after all these years. We replaced every sensor we thought could be causing the trouble, including the air-flow-meter, ECU, carefully checked all grounds everywhere, vacuum leaks; all to no avail. The engine just underwent an overhaul and the problem is still there! I surely thought the rebuild was going to fix it for good but it did not, darn!! The car was diagnosed by ALL the BMW experts in our area but none could not figure it out. One Tech told us that maybe some internal engine part got swapped in, which did not go to this engine, by the previous owner, who knows...any ideas anyone???

[beemer5]

there is a little black vacuum canitser on the top of the motor that controlls the fuel pushed into the injectors.. you could try changing that..

[elzo]

You mean the pressure regulator?? Did you have this problem before??

[beemer5]

on my car it had to much presure and was sucking down the gas, pushing the fuel into the motor I was getting about 13 mpg.. but if it just surges it may race the motor like you are getting..

[elzo]

well, I guess I'll try replacing the regulator and see what happens...