Help please: My 91 F150 runs rough / sometimes stalls when engine is cold
OK, my 1991 F150 had a rebuilt 5.0 about 4 years ago. Original otherwise. I drive it rarely (once every couple of weeks). Truck has been running OK except lately it started running rough and stalling before it warms up. The first time it happened I had lots of blue smoke from tailpipe. I thought I blew a gasket but smoke dicipated and comes back occasionally and only slighly. I can start back up usually, but need to floor the gas pedal and run on high RPMs for a minute or so and then it's fine. It's almost like it floods with gas and I need to burn it off. If I try to drive right away before the "pedal on floor" procedure, I am almost guaranteed to stalll once I start driving. Stall is most likely if I put into drive, if I let idle, it may be fine. I took it to a mechanic and he could not find the problem. Engine ran fine for him. Drove off and truck stalled on way home. Went back and he replaced coolant temp sensor and looked at distributor. Drove home but problem returned next time I drove it. By the way, the truck just passed an emmission inspection too at another shop (after it warmed up). I was actually hoping it would fail and they would find the problem, but it ran fine for them. Any advice? Neither mechanic doesn't seem interested in this job, too much of a headache I guess for not enough money.