136. A four-stroke eight cylinder in-line medium speed diesel engine has a firing order of 1-5-2-6-8-4-7-3. If #2 piston is at TDC and in the firing position, #4 piston is on ______.

Cylinder #4 is in the intake stroke when cylinder #2 is at TDC and firing. This is determined by calculating the crank angle difference based on the firing order and the four-stroke cycle length.