please help diagnose my ka24de dillema!!! HELP!

[Tastyratz]

ok here goes,i have a 93 240sx se with a blown motor,my friend gram and i just got a 92 240sx to part out, and the plan was i keep the suspension and the motor, but he keeps i/h/e/ j30 lsd.

so i started the car when we checked it out, fine. started it after it was towed to the house, fine. (got towed because the radiator cracked so it doesnt keep coolant pressure and overheats on long distances)after trying to go down the street a little the car bucks HARD and stalls a few times, i wondered if id get it back to the house. the next day when i checked it out it was very very hard to start, would start sporatically, and die almost instantly. at first it was diagnosed as a possible fuel or ignition problem. i cleaned all the plugs (new iridiums) and changed out rotor since it was weak. i swapped the fuel pump with my other 240's walbro, and i swapped injectors and fuel rail today. i ran a compression test and got 155-160-162-165 which is within the acceptable range of 151-171 in the FSM. it starts now pretty consistantly, but still dies pretty consistantly. i cant get it to run for more than 20 seconds or so. it sputters and jumps and shakes, then dies. the last 2 starts worried me. the brake booster vacuum line is cracked, and when it died thoes times blueish white smoke came out the line. the last time a big puff of that same smoke came right out the intake filter. the exhaust always smokes similar to that. when the car runs it seems to be running rich, with the occasional backfire. ive had a few suggestions, that it might be headgasket, or valve seals. anyone else might have a few ideas on this?????

[NISTECH]

well all signs point to the possibility it is a blown head gasket [ especially if the radiator is craked] But there is a couple other things you need to handle one is the brake booster line, if it is blowing smoke from it that means it either has a hole in it which could cause the car to run poorly or you have not connected it. the engine will draw air from that point when running, this air is unmetered by the airflow meter so it will not add enough fuel to kep the car running properly. fix this and retry. If you still have a problem with it then you may have a problem with the coolant temp sensor connection being corroded. check your conection for a green crust if it is clean it out and try again. I assume you have put the good radiator out of your car into this one to prevent it from over heating again. swap your distributor cap off your car too. and check your timing.

[Tastyratz]

i checked the guys records of the car it was just in on 10/03 for guess what... rough running and stalling at idle! it was diagnosed to a bad MAF

"traced condition to an intermittent high voltage from air flow meter to ecm at idle (1.3v) cleaned and tightened air flow meter connections, problem has not occurred since"

if thats the case, which i REALLY hope it is, that means i have an extremely simple problem.

[NISTECH]

yep. try wiggling the harness to the MAF while its running and see if it effects the idle quality. You may also need to add an additional grnd to the airflow as its ground might be poor. By the way 1.3 volts is not high if anything that is very slightly low.

[Tastyratz]

ok, update. since then i have installed my 300zx fuel filter to try it, tried advancing an retarding the timing by turning the distributer, checked for spark by checking if the plugwire will "arc" from the ignition coil to the distributer cap, changed out the ignition coil, changed out the maf and cleaned/checked all the wiring, and changed out the throttle body w/ tps. the throttle body seems to have made a good difference, i think the tps was actually bad on it. before the car barely started, and didnt run long or didnt do anything. if i started the car with the gas pedal down it would start and skyrocket, i.e. go to 5k rpm if i didnt let off. as soon as i let off the pedal it was like the pedal wasnt there anymore, the car wouldnt respond to throttle again, and just wind down from high rpm and die. it actually threw a code 11 the other day too, so im gonna swap out the distributor today to see if that makes a difference. by the time im done its going to be a whole new motor and have no choice but to start....

[Tastyratz]

tried swapping out the distrubutor, no matter where we time the thing we cant get it running again, im thinking its not because of the lack of timing since i think we did it right. pulled the plugs again and they were fully carbonized all over, but they were also soaked. there was oil all over them and oil going up the threads on them. oil in the cylinders = big no no. i would wonder if its the rings but they should be sealing because theres perfect compression right? would that point towards head gasket still?

[NISTECH]

was the spark plug wells ull of oil before you pulled the plugs by chance??

If it was clean the plugs ,replace the valve cover gasket put the engine at top dead center while the v/c is off [to be sure top and bottom are at top dead] get your old distributor put it back in and set it so the rotor points right at #1 on the cap. when the car is fully assembled try to start it.

The oil being in the spark plug wells will make it miss fire and run like crap.

[Tastyratz]

nah, oil wasnt on the top it wasnt coming from the valve cover gasket, it came from the cylinder

[Altiman94]

headgasket?

[jspecnitemare]

I had the same problem as you, plus my car would't rev past 2400 rpm without bogging. I finally fixed the idle problem though. Unplug different vaccum lines from your throttle body and see if that helps. I had cleaned and checked every single sensor and valve or so I thought, and I found this little valve under the throttle body with 3 vaccum lines attached. One of them went to the throttle body and I unplugged it, sure enough it purrs like a kitten now. I still can't rev past 2400 for some reason, but I think it's my MAF.