My 92 325i has started stalling and losing RPMs after it is started cold. It appears to be losing RPMs about every 3 seconds sometime stalling sometimes not. It has started hapening since the weather got below 20 degrees. After the temp gage gets 1/3 the way up, it runs fine. I ran diagnostics and it said to replace the Throttle Position Sensor. I did that and I still have the same problem. I have also replaced the air mass meter and that has not helped. Any suggestions?