ok so i just got done with my engine rebuild and now i have some problems. its running rich and i think it may because of the mass air flow sensor. that and when i was driving it to brake it in it got a oil leak. not that bad of one. but i was driving and my oil pressure droped a little like to the 1/4 mark. the other thing is that i will be driving and it will die but i think that it might be the mass air flow sensor. its a 3.0 v6 oh and when i go to start it it will turn over slow then when i try it once more it will turn over fast

 

I think if it was MAF sensor, It would start idle and die! Not sure I had that problem before, I could not keep the engine running no more than 4seconds! MAF sensor are $$

 

Sounds like fuel delivery. the reason it is likely starting better the second time is because you have pressurized the fuel system. My 88 does the same thing. I jumpered the diagnostics plugs so that the fuel pump comes on at "run" so I roll the key to run for a couple seconds and then "start" and it fires perfectly everytime on the first turn. I dont know where it is bleeding pressure and dont really care.

As for running rich dont over look the 02 sensor.

Rich-90 yota, it sounds more like you had a intake leak. Perhaps the simple act of replcing the MAF forced you to unknowlingly fix the leak.