I just installed an NTK 4 wire O2 sensor in my header collector. I'm wondering from those of you that use them, how do they perform in the collector of a long tube header? Mine reads around .95-1.05 volts at idle and I'm wondering if it's not getting hot enough for the sensor to read at idle. Do I need to drive the car around for a while to get it hot before it will give accurate readings? If it's not a temp issue then it must be a wiring or faulty sensor issue.

paulm
I've been doing a lot of research about O2 sensors, A/F and Lamda meters lately. Because I want to buy a true A/F meter. I'm not familiar with the NTK 4 wire sensor, but if the description says it's heated (a four wire should be) then you don't have to drive the vehicle to heat it up. It will heat to operating temp in about a minute. Also you will destroy it in a short time if you don't have 12 volts going to it for the heater while the engine is running. Some guys will run two O2 sensors and one gauge. This is ok but, you must supply both sensors with heater voltage while the engine is running, and toggle switch the signal wire to the gauge.
A little more info than what you were looking for but it all helps.
Jim

how many volts is a good mixture?

im using the same sensor in my shorty headers

Sounds like you are not getting the sensor hot enough. 1.00 VDC means very rich AF mixture (the car would not idle well when warn this way) or your O2 sensor not warmed up. Are you sure you have the right wires hooked up for the heater circuit?

Stoich (14.7 AF ratio) is from about .30 - .70 VDC with most narrow band O2 sensors. The O2 sensor is very responsive at stoich so the output voltage changes very rapidly when at or near stoichiometric.

It has four wires, two white wires, one black wire and one gray wire.

2 Whites - Heater One power, one ground
1 black - Sensor Output
1 Gray - Sensor Ground

I crimped and soldered all connections. I have one white going to the subframe as the heater ground, ignition power going to the other white, Gray wire connected to a valve cover bolt and the black wire going to the gauge. I wired as specified in the instructions.

The engine has always(since I got the carb setup right) idled and run very well. At idle the voltage is .95 - 1.05, so if it was really that rich it probably wouldn't be running very well.

I read somewhere that the O2 sensor has to be at least 600-800 degrees to give accurate readings. Do you guys have any trouble getting the O2 sensor heated when it's in the collector on the headers? How long does it have to run before it starts giving accurate readings?

I had the idle up kind of high(900 or so) to accomodate switching on the AC. I backed off the idle screw which caused the carb to get back into the idle circuit. The numbers starting changing very rapidly(like Eric mentioned) moving between .3 and .7. When I gave it some gas and got out of the idle circuit the voltage jumped to between .8 and .9. I think that I'm over jetted on the carb, since it reads rich like that? I have 43 rods and 73 jets in my Qjet, maybe I should drop down a jet size or two?

My heated 3 wire sensor is in my collector. Since it has a heater (its a 3 wire) it takes a few seconds after I fire the car to reach operating temp. Until it reaches operating temp it stays rich and reads correct once warm (like 30 seconds).

If you set your idle mix with a vac gauge and it still reads 1.0 VDC then you either have a bad O2 sensor or a wiring problem. It should read a low voltage (lean) when idling.

ps. I never ground anything to valve cover bolts . . . not sure if that's a problem or not.

I ran a ground wire directly to the negative side of the battery....no change. It's funny while idling or cruising it sits at .95, but when I let off the gas then it changes readings....whatever! Must be the sensor.

I tried a new sensor, this one is a three wire. It is much more responsive, but at cruise it reads .80-.85 which is still rich. Once I stop and idle it leans out though.

I'm wondering....with my QJet at cruise could the power piston spring not be depressed enough to pull the rods into the jets? I have about 15" of vacuum at idle in park. Maybe I need a weaker spring? It just seems funny that it runs so rich at cruise.


Actually after thinking about what I just typed....The primary jets control mixture at WOT and the primary rods control mixture at cruise. I think that since all QJet rods are "tapered" that the skinny end is the same diameter on all of them. The only thing that changes is the "fat" part of the rod which is pulled into the jet during high vacuum situations, like cruise. At WOT there is no vacuum, so the spring pushes the rod out of the jet and the diameter of the jet minus the diameter of the skinny part of the rod is what determines how much fuel dumps in.

Sorry, just thinking out loud here..... :D

[ 08-04-2003, 07:57 AM: Message edited by: paulm ]

I'm surprised that any 3 or 4 wire O2 sensor would recommend grounding to anything other than the guage itself. When you're dealing with signal values less than 1 volt, it won't take much of a ground current to skew the reading. I know the negative battery post sounds like a better arrangement, but actually it's worse. Instrumentation grounds should be isolated from the electrical system as much as possible. I'd ground at the guage, and then connect the guage to ground. This way, the only currents in your O2 sensor ground path are from the sensor itself.

-dnult

Have you guys seen this product/company?
http://www.techedge.com.au/vehicle/wbo2/default.htm