Hey, guys, hope you can help me out with this one by pointing out what to look for. Every time I fix something on my '91 V6 3.1, something new pops up. I'm about to drive her off a bridge.

SYMPTOM 1:
Soon after I bought the car, the check engine light started coming on about 20 minutes after driving it. The check engine light stayed on until stopping the engine. It wouldn't be there the next time the car was started. Because there were zero performance issues (no lack of acceleration or horsepower, fuel consumption was great), I chalked it up to a bad O2 sensor (I didn't replace it).

SYMPTOM 2:
About 3 weeks later, after replacing the electrical charging system, it was suddenly difficult to start (will start after 1-2 tries), the check engine light comes on immediately, but goes off after a while, only to come on again when accelerating (after which it will go off). Acceleration is poor and sluggish. Fuel consumption is absolutely terrible (10-15 mpg?). Because the symptoms were different than before, I assumed I might have pulled a vacuum hose loose or something but everything appears alright.

I haven't tried pulling the codes yet (paperclip method). I believe the EGR is new (OEM). Until I get a chance to pull the codes, is there anything obvious I might be overlooking?

 

Pull codes, report back.

 

The more I think about this, the more I'm looking at the O2 sensor.

Can anyone tell me where, on a '91 Firebird, the DLC port is? I'm not finding it.

 

Same place as all the others - above your shin when sitting in the driver's seat. There's a little plastic cover over it.