2012 S80 3.0T 150k miles. Hard to start in the morning. Take 4-5 sec to crank, worse in cold morning. If taking long to crank, it will trigger random misfire. But once it starts, if turn off immediately, the engine starts again right away. No issue with driving and the car accelerates fast. I parks the car whole day in an open lot. It seems I don’t have the problem (not always) to start in the late afternoon. This pattern repeats everyday. So far, I have replaced its battery and fuel pressure sensor, and also cleaned MAF sensor. Nothing changes. I wonder anything else may cause this problem? Other things in my list: coolant temperature sensor or fuel pump?

 

could be the temp sensor, could be fuel pressure could be an air leak. You can measure the resistance of the ECT sensor (google for temp charts but as a general rule its 3K+ ohms cold, under 300 ohms warm). You can also measure fuel pressure at the rail prior to and during start up - check youtube for vids. Your car has a variable pressure pump so check some other threads for typical values - it may start at something like 25 PSI then push up to ~55. If its lower at start up, you may have a leaky injector etc. Finally you could have an intake air leak so check vacuum lines, air boots etc. Any other symptoms like a puff of smoke at start up, low on power that could suggest other issues like low compression or a fuel delivery issue?

 

Wow! Thank you so much for the suggestions. The car is strong when driving. Idle stably at 600rpm. I got ave 21mpg for mostly local driving. Do you know how to hook a fuel pressure gauge? The rail does not have a shrader-type fitting as P2. It has a pressure sensor on the right side and a possible fuel injection pressure regulator on the left. Didn’t find anything for this fitting on YouTube.