Mark Hubley

I have an erratic idle, and I'm considering replacing my oxygen sensor. With 175K miles and the original sensor, I'm thinking this might be a good place to start. Two questions before I tackle the job:

1. Where does the wiring harness attach? I have the Haynes manual, and it has a section on removing and replacing the O2 sensor. However, it doesn't give me a good idea of where the wiring harness attaches. Perhaps someone could give me some advice before I get under the car.

2. How much should I spend on a new O2 sensor? Vertex advertises them for $74. Performance Products, Pelican Parts, and Tweeks are all upwards of $150. Are PP, PP, and Tweeks selling a better O2 sensor? Or are they just marking up the part way high?

Yes, I'm aware that many other things could cause my rough idle. However, over the past few years I have for various reasons replaced the distributer cap, rotor, spark plugs, spark plug wires, and air filter. None of these changes made any noticeable difference in the idle. At this point I'm figuring it's either the O2 sensor or a vacuum leak.

Speaking of a vacuum leak, can I test for this by spraying starter spray (what's the proper term for that explosive stuff you can spray into the air intake?) around the engine compartment and seeing if the engine revs?

Cheers,

Mark

7thStranger

Paragon sells bosh sensor for around 50 bucks. Can'nt remember exactly.
You will have to splice the wires but it's real easy.

Black wire to black wire.

then you will have two striped wires. They can attach in any order.

Joel

Or you can go to any auto parts store and buy a generic, single wire, Bosch O2 sensor for around $25. If you do that you'll have to crimp the wires together. One trick to getting the old O2 sensor out is to start the car for a minute or two to get the pipe warm. The old sensor should come right out. You will need either a large open-ended wrench (maybe 21 or 24mm - I can't remember) or an 02 sensor socket (which can be found at most part stores).

Keep in mind that a rough idle could be a sign of bad motor mounts too.

Joel

Oops...just the read post again. An erratic idle? Does the car hunt for the idle, like it swings from 2k rpms down to less than 800 rpms? If yes then check the connector to the idle stabilizer valve. The valve is located under the fuel rail and intake manifold. I just had the same problem with mine and it turned out the little metal clip that locks the connector in place was missing and the plug worked itself off. The stabilizer valve could be bad too.

goingboeing737

Go with the generic one.

Mine wouldn't pass emissions here in Tx. Got the sensor @ auto parts and had a muffler shop remove and replae it. It is hard to get enough leverage on the thing since it is in the top part of the exhaust pipe.

Crimped the wire. No problem. Passed like a champ.

Big E

Ugh. Hopefully you have better luck getting that sensor out than my father and I did. It ended up twisting off in the exhaust, we dropped the exhaust and somehow (and really, I have no idea how he was able to do this without screwing anything up, patience I guess) dad was able to drill out the old sensor, and then use a hacksaw blade to cut the remaining "ring" in quarters, after which time it finally came out. Most amazing, he was able to get the new one in without rethreading it.

Mark Hubley

I forgot to mention that the motor mounts were replaced back in January. That didn't seem to make much difference either.

Mark Hubley

Joel,

I don't think I would use the word "hunt". It sits at 1000 RPM, then every few seconds it dips down to 800. Never anything like swinging up to 2000 RPM.

erics944

Mine is doing the same thing. Except when it drops to 800rpm's the back end lifts up. I have an automatic, and thats the feeling you get when you take the car out of drive. I wonder if I have a transmission issue.

Luis de Prat

Mark, the aftermarket replacement O2 sensor for your car is the Bosch 15725, unless it's got the early kind like my 83, which is the Bosch 11027.

The early kind costs $25 at any auto import store. Late kind costs about twice that.

iloveporsches

Just ordered a new O2 sensor from Paragon. I know how rusted/ corroded my exhaust stuff is, so I'm planning on dropping my exhaust so I can work on it easier off the car.

josephsc

I did this the other day and used a O2 sensor removal tool (basically a 22mm socket with a funky shape). It made the removal and install easy -- no need to drop the exhaust to reach it. Bosch 15725 comes with a universal adapter that makes the splicing also very easy.

As for the location of the wiring harness, follow the wire from the sensor up around the bellhousing and up along the firewall -- the connector should be just infront of the firewall near the oil filler tube.

jharding

You're worried about a 200 rpm drop in idle? Does the car stall when the idle drops? If not I'd leave it alone. It could be just a dirty stabilizer valve. If you are so inclined, take the valve off and clean it. Check the vacuum lines too, however usually a vacuum leak will cause the idle to increase.

And don't forget to warm up the pipe before removing the 02 sensor. Of course after you warm it up don't forget to let it cool a couple of minutes so you don't burn you hand!

Luis de Prat

Joe, where'd you get the tool? Cost? TIA

Neverendz

The O2 sensor will not cause a rough idle. Clean the throttle body. Cheapest, quickest, easiest and most likely.