O2 Sensors vary greatly in price, I need one.

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'90 Volvo 740 2.3L 4cyl NA 180k. Indie shop informed me that fuel ratio is going too rich at times and the O2 sensor is likely the culprit. After scouring the entirety of the interwebs, I've discovered that prices range from $20 to $150 for this simple piece of kit. This Volvo is my beloved beater and I try to spend as little as possible on here, but don't want to regret going cheap in the long run. Thoughts?
 
I'd suggest going with a name brand like NTK, Delphi, Denso, or ACDelco.

Sometimes it's the little details that'll help with the decision making; like for instance in my application, one of the brands includes the mounting clip on the pigtail connector for mounting the connector to the connector support bracket; other brands don't include that.

PS. Make sure you check RockAuto.
 
I assume your Volvo has a heated sensor. My BMWs use a 4 wire sensor. 1 for the sensor, 2 for the heating element, the 4th is a drain wire to prevent interference. I used a 3 wire for a Ford 5.0. I hose clamped the drain wire cut from the original to th body of the sensor. and butt spliced the Ford sensor to the BMW plug. The 4 wire listed for 120$ the Ford was 45$ at Auto Zone. Both were Bosch sensors.
 
Before you order the new O2 sensor, do you have the data to prove that it is not working correctly? Remember, 90% of the professional mechanics are nothing but part changers. If you paid for the diagnostics, insists on the tests results which prove that the O2 sensor is not working correctly.

For an owner working on his car, part swapping is an acceptable strategy but if you are paying a professional, then it should be last resort rather than the first solution.
 
Originally Posted By: gr8gatzby
Indie shop informed me that fuel ratio is going too rich at times

Something doesn't sound right with that. O2 sensors generally don't fail that way when they die its a done deal.

When is going rich? Anything specific like every time it goes over this RPM or under certain conditions or just random?
Cracks in welds, joints or mounting points before the front O2 that open slightly when the car hits a bump can cause nightmares with fuel trim going rich.
Sometimes these are so small you don't even hear it but the O2 is effected by it and will call for a rich mixture.

Many things can cause what you describe but the one i suspect the least is the O2, it could be an intermittent connection in the O2 but i would want some sort of confirmation data before throwing parts at it.

Before buying the O2 make sure you order for the correct ECM, the Siemens Regina uses a different part. It will have Siemens or Regina REX on the ECM. The other ECM is Bosch.
 
I always recommend using the same brand sensor as the OEM. I have read complaints from people using a Bosch in place of an NTK or Denso sensor.

How do you the sensor is causing the engine to run too rich? One way to prove it is to disconnect the sensor, start the engine, and see if it runs better.

I recommend Rockauto for finding your sensor. Sometimes they will say what brand of part your car was originally equipped with.
 
The sensor can be checked with a meter, They dither between .2 and .9 volts if they are working correctly. If they don't make the meter dance, they aren't any good. The heater wires are usually white. The other color is what you want. Stick a small sewing needle through the sensor wire .Clip a jumper cable, alligator clips on 16 AWG wire, to the needle Put the other end on the meter's hot lead. Ground the other lead. Start the engine.
 
Originally Posted By: andyd
Stick a small sewing needle through the sensor wire.
Using a meter to test a sensor is usually done as a non-destructive test. If possible, backprobe at the connector rather than piercing the wire.
 
If the heater is bad it will set a separate code. I agree though watch the voltage when it's running in closed loop. The faster it switches the better.

Ultra-gauge is a good one for this, or Torque App for mobile phones, it's dirt cheap.
 
Originally Posted By: gr8gatzby
I ordered the Walker unit via Rock Auto.

Good sensors. Some time ago when i was investigating these it turns out they are Denso (it may have said NTK i don't remember) modules with the wiring and connector made and installed in the USA.
The connectors, wiring, color code, length match OEM. I have used plenty of them and like them, no problems whatsoever.
 
Fellas, I'm not sure how the indie shop determined that a new O2 sensor was needed. Instead of troubleshooting the old one, the new one will be here in a few days.
 
I recently ordered a bunch of clearance O2 sensors from RA for various cars; from 13 bucks to 18 bucks.

What I received were sensors in matching packages, but made by different manufacturers.

2 95 Honda accord sensors, came in matching Beck Arnley boxes, and were matching Densos (with diff length wires)

4 Hyundai Sonata sensors, two came sealed in Genuine Hyundai Parts bags, and both were NTK equivalent- one was actually an NTK (4ohm heater) and the other was anNTK knockoff by some Korean company called "golden". They were phyiscally identical. The NTK unit worked perfectly, the Golden unit was damaged from the package, two of 4 wires were broken inside the sheaths RIGHT at the sensor base, leaving no wire to strip and repair. I used pins stuck into the stumps with wires soldered onto them for testing. The heater on the GOLDEN sensor worked, but no output from the sensor. Given the dents on the GOLDEN housing, I assume it was sabotaged or damaged as a recovery part, which was subsequently sold to RA.

Two more sensors came, in Beck Arnley boxes. They did not match albeit being for the same application. One was a BOSCH knockoff made by GOLDEN, and the other was some other style of sensor, again made by GOLDEN. The Bosch Golden had outputs that looked good on a meter, but did not jive with the ECU. The other sensor, again great heater, correct resistance, but no sensor output at all.

In conclusion, I got the shaft. Out of 6 sensors, 3 were brand name (Denso and NTK) and were the only ones that worked. I have no desire to return them or grapple with RA over it.

Installed the pair of working Densos in a Pontaic G6, they work GREAT except for OBD2's horrible whineyness- OBD2 is unhappy that the heater circuits on the Densos are 14ohm, instead of 5ohm. So despite perfect sensor output and improved fuel economy, it throws a CEL. Eventually I'll purchase a match for that NTK (with correct resistnce) and install that pair.

So be careful with closeouts @ Rock Auto!
 
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