single or multiple problems?

[infinate_69]

my Auto 1990 240sx has several syptoms that im not sure the cause of. basically at completly random times there will be much less hp, max and accelerating. it almost feels like its in the wrong gear, but it is auto. sometimes when this happens if i turn the overdrive on or off it will change somehow, almost as if changing gears, and run better periodically. when it is running bad it will take high rpms to change gears and i have to let off on the gas for it to shift. when i stop and start to apply gas from a stop it will accelerate excellent for half a second and then hesitate for a second before resuming at a satisfactory rate. when any gas is applied the exhaust will be about 5 times as loud as normal and when gas is let off, much more backpressure and popping. the exhaust is custom but when running smooth it is not nearly as loud or intense with barly any backpressure noise. Another possibly unrelated issue, the valve cover gasket is always moist, as if there is a leak, but i have already had it replaced and the problem returned soon after. the only other thing that may be related is the fuel line or system because when these problems first started they were much worse but i found that the fuel filter was broken and getting clogged so i replaced it and now the symptoms mentioned above are all that remain. sometimes the car will run from good to horible twice or three times in a long drive but somtimes it will be perfect...i hope this isnt a stupid question and if anyone has any ideas and has read this whole feakin thing than your help would be greatly appreciated

[navysnail]

make sure you have a full tune up.it sounds like a sensor is out of whack and the ecu isnt telling the transmission when to shift at the right time. have you checked the ecu for codes?the valve cover gasket- did you make sure the mating surfaces were clean and free of gunk and debris and you used rtv on the little half moon thing righti will look into it a little more tomorow and get back to you with anything else.

btw- it is not a stupid question.

[infinate_69]

thnx 4 the advice, i will do the things u suggested and i think im gonna get another gasket just for the hell of it and make sure its done right. after i check her out ill get back to you on the condtion