CEL...O2 sensor?

[bluesman]

Hey guys,

I got a '96 V8 w/ 75,000 mi., 2WD. Check Engine Light came on about 1,000 mi. after I bought it. Autozone scanner said EGR, but they didn't have one in stock. I was leaving town that day, so I disconnected the battery for 15 min. and the light went out. About 1,000 mi. later, the CEL came back on. My local mechanic's scanner showed a bad O2 sensor. Put in new (Motorcraft) sensor, and 15 minutes later, CEL light came on again. O2 sensor shows 0.00 voltage when showing the error, but if I turn off the ignition and restart, the sensor starts showing voltage. The CEL is off now, but will probably come back on after 15 mins. of driving.

One clue, possibly unrelated. The first time the CEL came on was shortly after having an inspection station/oil change place check my air filter. Maybe they bumped the MAF sensor? MAF never shows up bad on a scan.

Any ideas? Thanks.

 

[Alec]

Have you checked the electrical connection to the MAS? It isn't a bad idea to clean it too.

 

[aldive]

Did you sscan the function of the O2sensor?

 

[bluesman]

Originally posted by Alec
Have you checked the electrical connection to the MAS? It isn't a bad idea to clean it too.

Alec, I'll have a look at the connection tomorrow. I'm guessing you're talking about cleaning "it", meaning the MAS. Yeah, I guess I could do that. I kinda kept that in the back of my mind, but figured the symptoms mentioned in that thread were rough running, and she's purring. I didn't want to complicate matters if that was not the problem. Keep thinking, I'm listening buddy. I'll let you know what I find at the connector.

 

[bluesman]

Originally posted by aldive
Did you sscan the function of the O2sensor?

Hey Al, thanks for the reply. Umm, not sure what you mean 'bout scanning the function of the O2 sensor. I don't know squat about the scanner, just looking over the local wrench's shoulder. I'm just watching it show the O2 sensor as the problem and 0 volts. Then after restarting the engine the 02 sensor shows fluctuating voltage like it has good sense. What else should/could I be looking for?

BTW, while I'll never be the mileage monster you are, I followed your lead and went synth front to back and am pretty pleased with my economy. Well, that was before this gremlin caused my EFI to go open loop.

 

[MrShorty]

I had an O2 sensor that would fail open, but only after it warmed up above a certain point. Normally it would work, but when I tried towing my trailer, it would get hotter than normal driving and fail open. but you said that you just put in a new O2 sensor, so I'm not sure if it would be the same problem. I wonder if you put a voltmeter on the sensor while the scanner was showing 0 volts if the voltmeter would also show 0 volts. That would at least confirm that the computer is reading the O2 sensor properly.