Okay guys, apex 240sx here again.

Well it's been almost 2 months now, and my '90 240sx still won't even start!!!!Here's description of what happened:For about 2 weeks prior to engine breakdown i noticed that i was burning oil, and occasionally, during higher revs, i noticed clouds of blue smoke from the tail pipe. Those only occured sometimes during high revs. And then about a week after i started noticing them, while driving on the highway at 60mph, my revs instantly shot from 3500rpm down to 1000rpm and wouldn't go back up. I had to put pressure on the accellerator to keep it from stalling. I let it stall eventually cuz i knew that the car wasn't going anywhere, and when i went to restart it, it wouldn't go, and ever since that day, about 2 months ago, it hasn't been running. Here's a list of all the parts replaced in the engine, and all the things that i've checked.-new fuel filter-new spark plugs-new distributor cap/rotor-new plug wires-new ignition coil-new air filter--the fuel system is opperating properly (engine is getting sufficient fuel)--the ignition system is opperating properly (everything is sparking fine)--the intake system isn't clogged anywhere (engine is getting sufficient airflow--timing is perfect--diagnostic showed nothing wrong--ECU diagnostic showed nothing wrong--compression test reported each cylinder at 135psiNow someone told me that 135 psi is low. If this is the case, then what would cause low compression in the engine, and cause me to burn oil. It can't be the head gasket though because the coolant system is of normal compression and there's no coolant in the oil, so that eliminates the possibility of it being the head gasket. I'm thinking exhaust manifold gasket, but would having that blown be enough to not even let the car start?? Any help on this topic would be GREATLY appreciated, because 2 months without my beloved 240sx is KILLING me, especially during the summer. Thanks to whomever can help me out..

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Sounds as if it is fuel related or timing related. Fuel pressure should be at least 36 to 45 psi. The ignition can be firing but if the timing can still be out. Fuel pressure and timing are not diagnosed by the ECM. Hard to tell but on rare occasions the dist shaft screw under the rotor comes loose and the trigger wheel or disc in the dist turns and causes the timing to advance or retard.

Ok, could be fuel related.

KA motors arent the best with head gaskets or MAFS.

Replacing the Mass Air Flow Sensor might solve your problem. Start with the easy first. While the engine was running (if you can get it running agian) unplug the MAFS and see if it will idle at least poorly. If it does run only with it unplugged then the MAFS is bad. Replace it and it should run good.

Next, TPS (Throttle Position Sensor). When these go bad, the car will refuse to idle and seem to choke the car while driving. The TPS is located on the side of the throttle body with 1 or 2 plugs going to it. Sometimes you can unplug the TPS with the car turned to on, then cut the car off and plug the TPS back in. Try to start the car and see if it did any different. Check your accerlation wires that go to your throttle body and make sure that when the gas pedal is 3/4 pressed the throttle body is completely open. After time the acceleration lines weaken and need tightening. It could have caused your motor to not get enough air and dumped more fuel causing it to faul out and even burn oil and gas.

Worst case: Head Gasket. Not all of the time can a gasket show signs of cracks by looking in the oil and coolant. Between the 2 and 3rd cylinders there are no water jackets so there would be no indication of a bad headgasket by just looking at the coolant and oil. however, you will burn oil and have rough idle still. A good way to tell without a compression check is if you could still get it to run. While the car running, pull the 2nd plug wire from the spark plug. Does the idle change and start idling rough? Then the same from the 3rd. If it does idle rough then it should be a good headgasket. If the idle doesnt change, then there is a good chance of a bad headgasket. There is more, but you need to start with the easiest.

If you unplug the mass airflow sensor and the car runs this doesn't mean the sensor is defective . The ecm goes into a fail safe mode when it sees the sensor open or disconnected in this case. It could be a improper connection or broken wire. The tps can cause some problems but in most cases it causes a flat spot on acceleration or a irratic idle. The mixture is controlled by the amount of air through the airflowmeter and the position of the throttle opening and other various inputs the cable controls play in pedal and full open throttle. With 135 compression it's very unlikely the headgasket is blown. With it blown between 2 cylinders you can get it started but it pings or rattles badly because it's firing 2 cylinders at once.

I have a 90 hatch with the SOHC and when I unplug the MAFS then the engine just dies. And I think my connector for the sensor has gone bad. And my car is smoking bad too (blue smoke) so it is burning oil. I have put new plugs, fuel filter, just had an oil change and the cat had collapsed or something so I bored it out. I just changed the PCV valve but the hose was dry rotted and came apart. I have to get a new hose but I cant even get to where the other end goes. Someone had told me that the pcv valve can cause the lifters not to function properly and it causes the engine to burn oil. So you might want to try changing the PCV valve. I know that my car idles alot better since the old one came off. Right now I am thinking I might just sell this one and get a 91-93 Coupe. I think I want a coupe more than a hatchback. Or maybe if I sell my Supra then I can just have both. Anyway, I know I am just babbling about stuff so I am done talking.

apex, your problem definitely sounds fuel related. I know when my pump went out, the revs would drop and even flooring the gas wouldn't raise them. Are you getting fuel out when you turn the key to on? If so, might be fuel pressure regulator.