hey everyone- new to this forum. I have a stock '93 Del Sol with a D16Z6 SOHC V-tec. It sat for 5 years after I git my daughter a different ride. Starts / runs / drives fine, no electrical problems evident ( everything works as it should).

When it gets fully up to temp, it still runs fine, tachs up to 6K+ no problem, pulls strong- no stumble or power loss. Sometimes when you come to a stop, and go to take- off it stumbles / cuts out / wont rev. Sometimes cycling key off/on will prime system and let me get through intersection.
Sometimes when driving steady state it surges , 2-4 sec of full power, 2-3 secs of power loss/ rpm drop. It will do this until I can slowly milk it up to say + 40 mph / 4K rpm it will start running fine and then do itagain after next stop.

I have replaced the fuel pump, main relay, filter, purged lines before and after filter. Also removed FPR and Fuel Return Vacum operated solenoid, cleaned and flushed them and the fuel rail. when cold it maintains pressure in fuel rail for several minutes, haven't checked it hot.

What signals the pump to shut off after the 5 sec prime on start up? Can the pump be shutting off / cycling due to an intermittant signal from ECU or a pressure switch I don't know about?

Help!!! gotta have it reliable so my son can use it for college daily drive.

 

Consider doing and full ignition system tune up - replace plugs, wires, cap, and rotor and adjust the ignition timing.

 

New wires/cap/rotor 5k miles ago.pulled plugs / all nice tan even burning.