My 91 v6 runner starts fine, revs up to normal start speed.. then and this varies.. but always struggles out..If I rev it, sometimes it prolongs it and then others is dies all the same.... regardless of what I do it never runs more than at most 20 seconds.. and this is with it gunned.

What could cause this?

 

could be the timing or a list of other things

 

I doubt its timing.. it dosent start rough... it starts right up.... Ive replaced the fuel filter and pump.. still same. Could it be something electrical or an sir flow adjustment? Pressure regulater?

 

Air flow meter or TPS. Also check compression to rule that out.