2002 Audi A6 3.0L Hard Start Issue- Can't Figure Out Help!
 

My car starts easily in the morning when it is cold. The issue is after I drive the car and park it for 5 minutes or more, it will be a hard start. It will takes about 5 seconds of cranking before the car turns over and starts. After the car starts, if I turn it off, and start it again, it will crank over and start immediately. I tried all the following with no avail. Any ideas or advice?

• Replaced fuel filter
• Replaced fuel pressure regulator
• Replaced crankshaft engine speed sensor
• Replaced coolant temperature sensor
• Cleaned MAF sensor
• Replaced PVC valve
• Mechanic tested fuel pressure and says it is OK
• Coolant reservoir does leak drip out of bottom after driving awhile
• Occasional check engine codes P0421 (Warm Up Catalyst Efficiency Below Threshold (Bank 1) and P0431(Warm Up Catalyst Efficiency Below Threshold (Bank 2)) but passed smog emission test recently