92 240sx problems

[JagKnight]

Hi guys hows it going? well i recently registered to this forum but ive been using for a long time for help with my 240. anyway here is my problem.

the first thing that was happening was that my car would lag badly in every gear it would bogg out whenever i gave it gas.also the CEL would go on and my car would idle horribly, it would start atlike 1300rpms and then begin to shuder all the way down to like 500 rpms and then spike back all the way to like 1100. i ran the codes and it threw codes 12(MAF), 32(EGR system), 33(front O2 sensor). i changed the o2 sensor. found that my bpt valve was bad changed that, and when i tested like 7 MAF sensors on my car they would all make my car die with the quickness, also if my car was running and i unplugged the MAF the car would die so i figured my MAF wasnt bad, ?. i reset the ecu and my car ran good for a while and then the CEL came on again it ran fine with minimal bogging in 1st gear. i ran the codes again today and the only one it throws now is code 32(o2sensor) ijust replaced my o2 sensor so my question is does anyone know what could be wrong with my car that could make my O2 sensor die or something like that? anyway im stumped but this is my first 240. so any help would be greatly appreciated thanks.

By theway my motor is completely stock except for a k&n cone filter at the end of my intake to replace the stock air box.

[s13sr20chris]

oem o2 sensor?

[JagKnight]

yeah its the universal o2 sensor i unplugged it and it ran better for a while i drove it hard today redlining differential locking and all that good stuff and on the drive home my CEL came on and stayed on so im gonna wait to hopefully do another diagn. tomorrowby the way thanks for any info

[NISTECH]

Chris meant is it a factory O2 which obviously its not. I have come across a single 240 about your year that had a problem with the wire where it comes off the back of the valve cover harness loom, about mid way down to the sensor where the tie wrap is it was shorting to the braided shielding in the wire insulation. This was the only 240 I had the problem on but it kept throwing the code even after the O2 replacement. Thats what lead me to checking the wiring. What I did was cut the wire at the back of the valve cover ran a single wire down to the O2 soldered it at the top and down at the connector for the O2 insulated the **** out of each end with a special type of self adhering elctrical wrap(to keep out moisture. while I had the connector end off I slid a braided wire tube over the single wire and slighty over the original braiding in the harness , this braid ran from there down to the connector for the O2. I then sealed the whole stretch of wire with the electrical sealer tape. That is what fixed that car.Since your not using the factory O2 though this may be why your getting a code as well. Those universal O2's are not that great.

[JagKnight]

cool dude thanks ill have to check that out.

the weird thing is that i disconnected my o2 sensor today just to see what it would do and while the engine was kinda cold it ran like a champ, mad torque and really quick on the rpms with no lag. when it got warmer it didnt have as much power but still ran a helluvah lot better. so my new question would be why?

thanks a lot bro

[NISTECH]

The ECM doesnt look at O2 values till the car reaches operating temp, I believe that magic number is 158 degrees. then it starts using the o2 to fine tune the mixture for optimum performance and fuel economy, if your o2 is out of the loop it reverts to the cold start up sensors and uses a predetermined map to guess the best mixture. But when the car is cold it uses a richer mixture to help heat it up faster. The effect of the o2 is minimal on your cars performance as it only really works when the car is at cruise speeds and idle. when you are accelerating from a stop[assuming you dont drive like grandma] it goes into what is called open loop[o2 is taken out of the equasion and a fatter mixture results. basically anytime the throttle is in the neighborhood of 60% and above the ecm quits looking at the o2 for mixture control.

[s13sr20chris]

you know whats funny? the newer cars use the o2 even less. now they dont watch it at idle either. its getting be a steady state cruise only thing. wierd huh? i heard that from an instructor at tech school and verified it by watching consult. newer nissans idle in the super lean zone. alpha in the 110% and up range.

[JagKnight]

well thanks for the tech data.

i guess i really havent ben able to get my problem across i ll try again.

when i drive my car sometimes (more often than not) it lags really bad. ill have the accelerator in all the way and i wont be going anywhere untill i hit about 3000rpms then my car will lunge forward and pick up a little better but still not nearly as well as it should. i thought that maybe my plugs and wires were bad so i did the tune up (plugs, wires, cap, and rotor) when i took out the first plug though there was mad (i mean really bad) oil in the hole where the spark plug goes (sorry i dont know the tech term) not on the electrode or the theads or anything not like in the cylinder but just the outside of the plug (it was like a puddle or something) so i went ahead and replaced my valve cover gasket while i had the plugs out. the car ran real well for a couple of days and then the CEL came on again on and off. it would come on and if i stepped on the clutch and tapped the accel. it would come off. it was like that for like a week untill the day i drove it and it ran like crap, lagging and then lunging in every gear, thats when i ran the codes and it gave me the o2. like i said on the previous post i disconnected the o2 and now its running decent, not great but not bad either. the CEL didnt come on for like maybe 4 hrs and then it did and stayed on. and thats where im at now. if it wasnt cuz im trying to pass smog i wouldnt stress it so much but im at the end of my ideas and i dont know where else to look i tried searching for a while but couldnt get any info. anyway sorry for the lengthy post but if anyone has any ideas i would really appreciate the help and thanks again for all the prior info.

[NISTECH]

its possible that when the throttle is in the range it needs to moniter the O2 the signal is extreamly low or extreamly high(off the scale) and the ecm is trying to counter what its seeing by either leaning it way out or richining it up to the point its flooding. the fact you can unplug the thing and it runs better suggets the o2 is garbage. get a factory O2 installed and see if that makes a difference for ya.

[JagKnight]

sounds like a plan ill do that and let you guys know whats up.