I need help. I just had the rack and pinion replaced,it is rebuilt, on my 2001 325i BMW. Now it has a very rough idle and is stalling. Stalls at slow speed or when moving off. I returned to the mechanic for a few days and they said something about a sensor? and that it was running well and ready to go. I retrieved it only to stall multiple times again, last night and this morning. So now I am once again returning it to the mechanic. They are talking about my o2 sensors but why did I not have this problem before replacement?? I feel its correlated to the rack and pinion. Your opinions will be greatly appreciated, very frustrated so not mechanical. Thanks so much!
The rack and pinion should not affect the engine's ability to operate as expected.
If the car ran and drove without issues, other than what the rack and pinion were replaced for, then the mechanic did something to cause the problem. They most likely damaged a sensor or wires when removing and installing the rack.
Check the laws are where you live to see what protection you have. Where I live, if the mechanic is unable to fix an issue they cause, the owner can take it to a different mechanic for repair and the bill the first mechanic.
Sounds to me like the line from the oil separator to the dipstick got damaged, it passes near the rack and pinion and can be seen by looking down into the motor from the driver's side, between the motor and power brake booster unit. It's not easy to see at first but if it got damaged, it will cause a vacuum leak which will have the symptoms you described.