Title pretty much says it all.

Finally got a chance to focus on 86 car.
Symptoms were strong gas smell from exhaust, about 50% increase in gas consumption, felt like running on 6 cyls unless coaxed over 3500 rpm..at which point it smoothed out some.

Bought new model specific bosch O2 sensor.
Dropped exhaust, installed it.
Touched nothing else. Had a list, but started with sensor first as suspect.

Runs beautifully now. Something simple for once.

As our 928 brother JHowell always says, if you hear hoofs dont immediately go hunting for zebra, ie, it's probably not that exotic of a root cause.

That said, full disclosure, I've been obsessing mentally for a year about it before taking meaningful action. Just sayin.

Chris

 

Glad it was something easy ,
any idea what was wrong with the old O2 sensor?

 

Not certain. I tossed it. Honestly, it was generic bosch, cobbled, short wire, non factory connectors. I remember taking short cut on this about 6 years ago when I was sick. I think the crimp connectors were damaged by me when I did CE panel service two years ago. Didnt verify. Should have.

I dont think was silicon poisoning. I did an intake service 4 years ago but didnt use any silicon lubes on boots or such.

 

It’s time that when we have our exhausts removed, to take the opportunity to visually examine the catalyst matrix. This is easily done from the rear of the cats. A cheap boroscope can view thru the front. Heat from Periods of rich or lean burning takes a toll over 30 years. My matrix was broken, with no hint of external impact and had to be evacuated.
really… just considering the age

 

They are wear items and should be periodically replaced.