Recently I picked up a 1991 190E 2.3 4 cylinder automatic with 139K miles for a spare vehicle. At times the car does not want to shift up to second gear unless I step on the accelerator to force it upward. Is this possibly vacuum line related? Any help would be greatly appreciated!

You are most likely waiting for the upshift delay for the catalyst to heat up, emissions. Should be normal once it heats up.

Thanks for the advice...I'll keep my eye on this.