Please help!! code 33 wont go away!!

[peptobrian]

I have a 1995 240sx se and have replace the front 02 sensor twice now and still have code 33......the first time it went off for about 4 months the second time about 1 month. The car is running good, no back fires or anything. Anything would be helpful. Thanks

[Wc240]

just becouse it says o2 sensor, doesnt mean REPLACE THE SENSOR. especially on obd 1. it means that the 02 is out of its perameters. this could either be that A: the harness between said sensor and ecu is mangled/compromised/jacked, orB: your motor is running bad enough that the level of oxygen that its reading(or not reading) is keeping it far out of the voltage specs it needs to be(wich is only about .1 to .9 volts, orC:you have an exhoust leak above(see, before) the sensor.none of wich would couse a backfire, but may couse a hesitation, running rich, lean, slightly to heavy drop in MPG, all depends on what exactly its doin

[peptobrian]

Thank you......any suggestions on how to diagnose it. Besides the obvious?

[peptobrian]

I put a voltmeter to the 02 sensor and got .53 does that mean that its runing rich or lean and what are some stuff that I can do to find the problem at that point.

I also check vacuume lines all is well, checked plugs they aren't black just normal wear. No power loss.....

Any suggestions?
Modified by peptobrian at 1:28 PM 10/23/2009

[Wc240]

all meters(that i know of, including my $375 one) are just not capable of caching the trace. best way is a DSO, those are expensive. .53 would be slightly rich, but remember, that things supposed toi be switching 10 times a second, from rich to lean. instead, unplug the sensor and try to ohm out/check the resistance from the plug to the terminal at the ecu. also, the resistance from the sensor to ground(with it unplugged.)

[-RJ-]

I had that too on my car. I knew my injector o-rings were bad so I replaced them. The light went away a day later

[Wc240]

^^^thats what i was saying. if it goes too rich or too lean, the idiot obd1 computer is gonna say its the sensor

[peptobrian]

O nice to know thanks.....BTW i went to pull off the fuel rail to see if any of the injectors was leaking and as i tried to tighten the bolts that hold the fuel rail on the intake manifold, the threads in the intake manifold broke loose and now there is nothing for the bolt to screw into. Should I look into getting an aftermarket intake or is there a way to fix it?Thanks again you guys are a lot of help.

[-RJ-]

could try taping it