Hey friends I am completely at a loss been messing with my 1991 240sx ka24de since the first day it was salt free and warm.... ok here we go ...... I started it up any time the snow would melt over the winter started like a champ every time... i take it out on her spring maiden voyage and it was good for about 5 miles then suddenly it starts idling really rough like so hard if i said ahhhhhhhhh loud in the car it would sound like i was bouncing up and down. so i say well its got to to be it needs a tune up or just to be driven a bit b/c it wasn't run hard over the winter just idled and reved for a bit . so i drove it ten miles to my buddy's place and it surly didn't feel like it had the power it once did. he thought it might be the injectors so we took them out cleaned them off popped them back in and the idle got violently rough and it wouldn't want to stay running unless i kept on it. so i had no choice but to drive it home pedal all the way to the floor and i was barely getting 80 out of her. it used 1/4 of a tank of gas for 10 miles back home WTF... next i think its the injectors so i go get 2 complete sets from the junk yard doesn't change anything, then i do plugs wires o2 censor cap and rotor still nothing changes. i was told by a 240 guy to check the oil it might have gas in it if i used that much gas. sure enough i changed my oil i kid you not 3 gallons of fluid gas/oil came out. yadda yadda i pull ecu read the code its reading knock sensor so i go get one from the junkyard, nothing changes, try another ecu nothing.. i tried to look over the vacuum lines the best i could didn't appear to be any issue with them/ also did the carb cleaner test with them. im about to give in to a raping at my local garage to get this thing fixed so as a last plea for help before my wallet takes a beatin' i decided to see what you guys have to say.
I would really appreciate any educated input you can give me !

If you managed to drain 3 gallons of fluid out of the oil pan then you have real issues. Did the oil look milky and brown like chocolate milk? You could have coolant in it which could be a cracked head or block, or a blown headgasket. How much coolant is in it now? If that motor was holding 3 gallons of fluid in your oil passages/pan your valve seals are probably shot from the leakdown from above. They seal out a certain amount of oil, but won't take a flood like you are describing. Thats why its important to not overfill with oil.

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Are you leaking fuel out of the rail at all? Bad o rings on the injectors? Hole in the gas tank? Split fuel line? Run it and check for leaks.

I am also at a loss to explain how that much gas is getting into the oil.

The olny time I have seen gas milage go that bad that fast was when the Cat was plugged. But that does not explain the gas in the oil.

If your injectors wer putting that much fuel in the engine then you shoud have large amounts of black smoke out the tailpipe.

Sounds like you may have to tear it down to find the problem.

Dirt is for Racing, Asphalt is for getting there. Have fun, Play in the Mud.

Do a cylinder compression check on all cylinders. Pull the fuel pump fuse and and check each cylinder at one time. Dont pull all the plugs out and try and get readings. Doing so will affect the test (causes the engine to turn over too fast cause of no compression) Get some readings, I bet you are low on at least 2 cylinders. I think avg compression should be around 160/175 psi I believe. I might be wrong on this please check before going with these numbers. This will help with figuring out whats going on. It will tell you want cylinders are having issues.

Modified by fenderfatstrat6 at 9:58 AM 5/16/2008