Randomly will not idle.

[JustinS40UT]

All,
I'm having a very weird issue with my 2003 S40 and hope you guys can help shine a light on the problem. Symptoms - Randomly will not idle, starter is works but will only fire up if I apply the gas. I can achieve an idle after 10-15 minutes of running the car at 1k-2k rpms and slowly back off to test if the car is idling after getting it going it fires up fine unless left for periods of time of 8+ hours. What I mean by random is that one day it will have these symptoms and another day it will work fine. I've left it with my mechanic for over 2 weeks and it fires up fine for him when I get it back doesn't work. I haven't identified any environmental conditions that are contributing to the problem. The mechanic did get one code and it pointed to the MAF we replaced it but no change put the old one back in and no difference there either. Let me know what I should check I'm going to purchase a OBD to get codes when they come up.