1993 240sx driveability help

[jman211111]

1993 nissan 240sx.engine is ka24de engine was 2.4L, but bored .50 over,engine has 1,300 miles, and car has 132,375 miles. ok the car lacked power and would sometimes whant to die before the rebuild and had oil in the cylinders so i checked the head gasket it looked ok and i noticed the pistons wabbled in the cylinder alot in all directions so i decided to rebuild it and the cylinder head. wile i was putting the engine back together i compaird the pistions and noticed the pin to piston deck hight was difrent and also it looks like the engine has been rebuilt before so i figerd this must be my problem. well it has more power then befor but not as much as it should stock from factory it runs around 16.00 1/4 mile mine is now at .50 faster then before at 18.053 witch is comarible to a gio metro lol. I waighted to take the car to the track at 1,200 miles to let it brake in. now ever since i finished the rebuild before the drag strip it has had a rough idle and semes to have a poof that can be heard in the exhaust but is not a misfire poof and as engine rpm incresis so does the poof so i checked distributer timing and made shure the timing chins where corect and they are . also it seemes to have a flat spot at @ 1500 at slow to meadium throttle increase and smothes out at wot. so i checked the throttle position sensor and it tested out of range so i replaced and retuned the car and reset the sensor like the repair manual sead to so the problem was lessend (engine runs smother) but is still there.i also try replacing the maf with a used part but it made no differance. the car also backfires in the intake at times so i checked the egr but the repair book only sead if it moves up when you rev the engine it is good but i noticed it can move up more then it actualy does but this repair book dont give me a diffrent way to test it with a vac gauge or anything so i dont know what to do about that part. and today i noticed when i apply a electrical load llike the power windows or even turn on the head lights it seams to whant to die so i took it to autozone and the charging sys checked ok at the battery (alternator was not bench tested) and the battery had a dead cell so i replaced the battery but it did not make a diffrence. I also checked the cat and it was realy clean with no debris in it at all.i also have a cold air intake so i replaced it with the stock unit to see if it makes a diffrence but it dont.I put a fuel presure regulator from the junk yard and still no diffrence. I replaced the fuel pump about 2 mounths before the rebulid because the orriginal whent out. i got some used injectors and a injector reseal kit and no diffrence. i replaced the ignision coil because the secondary ohms were out of range and it made it run smother but still the same. i replaced the pcv valve it runs smother but still no diffrence. I would check the ecm but ether the repair manual or me know how and it is pre obd11 so i cant find anyone who can plug into it and there are no DTC's. and ecm conections look good and clean. I also noticed when the car is runing and i check voltage at the battery it is at 14.3 and when i turn the head lights and blower motor on full blast the voltage at the battery drops to 14.0 is this normal or is the voltage reg bad, also it has .50 ohms on the cable from the alt to the battery. and i could not find a addjustmint for the idle air control valve.engine vacume is within spec at idle and when i rev it it loses vac(or goes more positive) and then go's back to more vac but more then at idle and the neddle movment is a smothe movement. One thing i noticed was the cam has some where marks on the lobes so i asked the machine shop that machined the block and heads (they also installed and clearenced the valve spacers) if that was ok and he sead its normal but i seen a small grove in one of the exhaust lobes on the #2 cyl, but all look like they have scuff like marks on them, and i checked the clearence and it is perfect on all valves. Also before i replaced the pcvi replaced the spark plugs and the old ones had a white grainy buildup on them. and the o2 sensor has also been replaced and reads steadaly a bit above 14.7 to 1 air/fuel ratio. so i think thats all that is going on i hope you can help me because my brain really hearts lol.

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Modified by jman211111 at 9:32 PM 11/15/2007