92 toro running problems

My buddy has a 92 toro with 3800 and is having some trouble with his motor running/idling. One time he starts it, it runs fine. next start it wont stay running and seems to be overfuelling (bad blue smoke). Kinda wierd i thought. I went over and changed his pressure valve in the rail and it ran better for like 5 minutes and then went back to missing and smoking. Shut it off and then it runs fine again for a few minutes. Any ideas what to start with next? thanks

Run a scan look for MAF issues, coolant temp sensor stuck on cold temp input, check fuel pressure also, a leaking injector is also possible. Blue smoke is usually not a fuel issue though, make sure the oil is not overfilled.

ok. i will try them. thanks

Appears MAF was to blame. thanks