Replaced the 02 sensor in my 89 and STILL throws a Code 13?

[nailbomb3]

Guys, for awhile now I've been throwing a code 13 and getting just lousy milage in town, around 12 MPG at best.

So, last night I decided to replace the O2 sensor, picked up a Bosch at the local O'Reillys. The old sensor
was just hammered, black deposit near the threads, and white at the tip.

Put in the new sensor, and started the car and shut it off like 4 times on my trip home from my friends, NO problems.

Went to start it this morning, and after driving it for awhile BOOM there is the Code 13 again. I did the paper clip check and sure enough it was back.

Note, I DID pull my negative cable after doing the swap to reset the computer, so I know this isn't an old code coming back.

At THIS point, with no other codes, what should I do here? Do I need to maybe clean the MAF sensor? Getting a tad frustrated.

Thanks

[J Wikoff]

Don't use Bosch stuff. I wouldn't expect immediate failure, but not long life.

First I'd look for wiring issues, then vacuum leaks.

[nailbomb3]

Thanks. What's the issue with Bosch stuff?
Where Where should I be checking for vacuum leaks and how?

I remember there used to be a factory service manual online but it looks like it's gone now
:-(

[MattStrike]

Are you having other issues? Misfiring or anything?

It's most likely a wire or connector terminal that has gone bad.

Vacuum leaks are typically at the rubber joints for the vacuum lines (or rusty lines), or can be at the gaskets on the intake or throttle body. Basically any point past the MAS will cause issues. They can be found using carb cleaner - but be extremely careful with that if you like your hair - give a short burst spray on a suspected leak, and if there is a vac leak the idle will either jump or or it will nearly choke out the engine. Also note, do not get it anywhere near the MAS.

[nailbomb3]

No other issues, it runs pretty dang smooth. Just that milage is horrible. No other codes than that code 13 ever show up.

How can I check the wiring past the sensor? I've got a pretty nice Fluke meter laying here

[MattStrike]

It's probably just an intermittent issue, as it went several days before throwing the code. It might be a connector terminal is either oxydized or the spring tab inside the terminal is bent. A visual inspection to make sure the spring tab on the female pin should touch the roof of the pin, and for other oxidation or goo or something, if it's gapping then it's suspect and should be re-sprung or splice a replacment pin in.

Otherwise a continuity test between the connector on the sensor and a connector on the PCM is in order. Unless a mouse got in the car, the wire can only break at a flex point.

[nailbomb3]

I'll take a look at when its a little warmer out thanks!

Actually with the OLD sensor, it would throw it intermittently, the new one started doing it within hours.

I DID clean my MAF today, and mannnnn it was pretty dirty!

Will report back.