well my 1990 240sx ka24(E) is miss-firing, has about 10lbs of crank case pressure and vacuum, it seems to work ok above 4.5k rpms, iv tested the ijectors. we tested the vacume lines for presure they seem fine, and did a cylinder compretion test they are all close (within 8lbs), im burning oil and losing water a little at a time. my gas milage is like 18mpg hiway, and well i'm at a loss sence this is uncharted taritory for me, i suspect for many of you aswell. oh yea it was runing ok when i first got it and even then it had pressure and vacume in the crank case. oh and my valve cover gasket is leaking oil on the header cover, and on the intake manifold because of the crank case pressure. so yea i need some real advice here.

 

the numbers being close for the compression test is not enough. generally 140 -160lbs within 10% is good.

sound to me like your timing is off or any of your ignition components are faulty. you should inspect and if needed replace your dist. cap, spinner, wires, plugs, pcv valve, air filter, and o2 sensor.

all these are possibly responsible for you misfiring and poor gas millage.

 

well what about the constant pressure and vacume on the crank case it feels like its one cylinder ,like i may have bad valve seats, or a blown head gasket. most likely the valve seats. i cant tell if its exhaust (in the crank case) or not cuz i do have a header bolt missing and can hear it leaking by a high pitch repetitve hiss the same repatition as the rpms. so it always smells like exhaust in the engine bay. im not shure if its normall on this engine, for that pressure and vac, i can feel it when i open the oil fill cap i dont know why but the engine doesnt bog when i open it.
????? im very confussed whats going on with it?????

 

well any one there?

 

i dont understand what you're trying to say.
how are you having pressure and vacuum in the crankcase?
how are you measuring pressure from the vacuum lines?
excessive crankcase pressure is probably a bad PCV valve

 

Have you measured vacuum at the dipstick hole & PCV valve?

 

yes ive tested the pcv. you mesure vacume line pressure with an inline gadge on the line from the intake manifold.

iv not messured at the dipstick. i have at the pcv.

well i talked to a machinic about it, aparently i have busted piston rings or busted piston alowing the air in the cylinder to excape, ergo the pressure and vacume in the cranck case. oh and i am figuring that im loosing water because i have a busted head gasket between the water jets and the cylinder. the oil coming out the valve cover gasket is from the air pressure from the busted piston rings. i think im going to take advatage of this situation and get some high performance pistons, cam, crank, star cut the valve's, and a basic overhaul with perfomance parts. mabey spend about 1500 on the engine and take her to 0 miles on the engine. nothing to extream for now performace wise. hopfully ill finaly get the engine i've been looking for. so ill update on here the status of the motor. i got to do a complete tear down next weekend to find all the problemes. yay! fun

 

if you had bad rings then the compression test should show it. especially by the reading of the gauge on the first crank rotation.

you cannot have pressure and vacuum in the same place at the same time. it's one or the other.

you're going to need more than 1500 for pistons, cam, crank....... and wtf is star cutting the valves?

 

yea i now. star cutting is were you put grooves in the valves to direct the spread of fuel in the cylinder. yea you can buy stuff alot cheaper than mainstream prices all you got to do is look around. pressure, vac, pressure, vac, pressure, vac alternating.

 

star cutting sounds interesting.
you have any material you can link me to?

 

That is a BIG misconception. Not true at all.

 

care to explain?

 

what were the numbers you got when you checked compression? also, when you try to start it will it stat right away?

 

sorry college home work got piled up. umm i'm not really sure what the numbers were i think it was 20 psi steady when i first got it, right now i'm not shur what they are, thats what i was trying to say, its goten worse and that i hadent tested it sense 3-4 months ago when it sounded alot better. yea it starts nearly perfect sometimes is slow to start.

well i've herd of groving the valves from a guy i know in austin with a nice celica. anyways i'm not realy sure whats envolved, or why it is done other than directing the fuel. i know the performance of an engine is really dependent on how atomized the fuel is. for better explosions its better to have the fuel particals seperated and furthure away. sense its not the fuel its the fumes that are extreamly explosive. well i understand it but im having a hard time putting it in to words. anyway its farly easy to misconstrue intint of a individual that is trying to impress you so it may be totally false, i'm looking in to it myself i'll get back to you on it though.

 

20psi9 on the vacuume line