O2 Sensor Problem

[sukebe]

You can skip this story and go straight to my question at the bottom.

Okay, my car has been running rich for a while and my gas mileage is terrible (<20 mpg) so after changing plugs, wires, cleaning MAF and EGR I am going to replace the O2 sensor (not sure when the previous owner changed it last).

So anyway, I get under the hood and realize this is going to be a bitch if I dont remove the heat shields... easier said than done. After breaking 2 bolts and a lot of cursing, I finally got it off and out. (I'm sure it will take me 5 seconds to put that SOB back in) :madfawk:

Next, I try to tackle the O2 sensor. Sprayed with penetrating Liquid Wrench and let it sit for a bit. Then, I got a 7/8 wrench (read this in a diff thread... thank you search button) and attacked it. Well, since the box end only works on the corners and the sensor is made of some sort of weak material (like butter) I almost rounded all the corners over. The open end can't really grab the sensor because it's slightly too big.

My question (FINALLY): Did Nissan O2 sensor come in metric size? My Bosch replacement part is 7/8, but I'm wondering if the dealership or factory part was metric. It makes sense since it is an import car. If, in fact, there is a metric part, what is the proper wrench size? 22mm?

Thanks in advance, and sorry for the novel. I had to take a break for a while and vent. I can't have a beer yet because, the way this is going, I probably wouldn't stop!

[Modern Angel]

I just replaced the O2 sensor on my '93 KA a few weeks ago and it's really not that hard. Certainly no need to remove any heat shields (unless the previous owner had already taken mine off, which I doubt since my sensor was obviously the original...) Anyway, just use an O2 sensor socket for your ratchet and the install/removal should be fairly easy. It's pretty tight in there so it's kinda hard to move around (banged my hand up pretty good breaking the sensor loose) but other than that I didn't really have any problems. :)

[idlafie]

Sukebe
Yep...used a Sears Craftsman 22 mm open ended wrench to get my 02 sensor off. You might want to check your Engine Coolant Temperature Sensor if your car is running rich & getting crappy gas mileage. Your 240 takes the signal from your Engine Coolant Temperature Sensor & adjusts your fuel/air mixture from that. It dumps more fuel in when the car is cold so as to heat up the catalytic converter faster & reduce smog. If your ECU thinks that the car is still cold AFTER it warms up, then it will continue to dump more fuel into your intake causing your gas mileage to drop. Most likely your problem is the Engine Coolant Temp sensor and NOT your 02 sensor.
Anyhow, hope this helps..
Diego
'95 SE

[sukebe]

Thanks!

I finally got it off, but only after buying a 22mm wrench.

Good news is, replacing O2 sensor helped with keeping my idle ~700RPM.
Bad news is, my car is still running fat.

I'll have to check the coolant temp sensor. Good looking out!

Is there anyway to check or test it short of buying a replacement and swapping?

Thanks again!

[idlafie]

Didn't see it in your post, but what do you have? A S13 or S14?

On the S14, you test the Engine Coolant Temp sensor in a small pot of hot water. Put the sensor tip in the water & heat it up. At 68 degrees F the resistance should be 2.1-2.9 kiloOhms. At 122 degrees F, should be 0.68-1 KiloOhm, at 194 degrees F, should be 0.236-0.260 kiloOhms

Considering how old your car is, it's just better to replace it & save yourself the hassle. You migh burn yourself with the hot water!!..hehehe..

Deigo

[sukebe]

I have an S13 coupe (1990):(.

I was thinking I should probably stop being such a cheapskate and just replace it anyway. It's old, so chances are I'd be replacing it down the line anyway. Might as well change it out on my schedule.

Thanks again for all the info! I'll post back when I get it done. I really need to pick up a FSM...

[sukebe]

Well, replaced the coolant temp sensor for $15 from Kragen's. Hardest part was tracking down a store that had it in stock. Changed it out in about 5 minutes, but the plug harness was so old and brittle from heat that I broke a bunch of it off... oh well, it still makes a pretty good connection.

Haven't reset the ECU by turning to Mode IV (not sure if thats the right mode), but I did disconnect the batt neg term for a couple minutes. Will this be sufficient? I guess I'll find out after I drive the car around a little.

Thanks again to Diego. You are the man!

[Modern Angel]

Well, replaced the coolant temp sensor for $15 from Kragen's. Hardest part was tracking down a store that had it in stock. Changed it out in about 5 minutes, but the plug harness was so old and brittle from heat that I broke a bunch of it off... oh well, it still makes a pretty good connection.

Haven't reset the ECU by turning to Mode IV (not sure if thats the right mode), but I did disconnect the batt neg term for a couple minutes. Will this be sufficient? I guess I'll find out after I drive the car around a little.

Thanks again to Diego. You are the man!

Disconnecting the battery for a few minutes should be sufficient to reset the ECU. It was good enough for the OBDII ECU in my '97 Prelude anyway... :)