turbo issue on 1995 850 sedan

[john_dakins]

thanks in advance for reading this....My 95 850 Turbo, 170K miles has this pattern with the turbo:

1. very little boost, can hardly get it into the white, no punch.

2. hard codes are 4-3-5 "heated oxygen sensor, slow response" and 4-4-3 "TWC efficiency".

3. After I reset the codes - and especially after I disconnect the battery, the turbo works just fine - for a day or two. Then it looses punch and a few days after that, the hard codes will come back.

I've replaced the vacuum hoses and I am pretty confident that they are ok.

It has done this enough times to be a pattern. Can the oxygen sensor and catalytic converter have that effect on the turbo?
What should I do?

I'd appreciate any help - If I didn't love this car so much, I'd give it the boot - but...well - you know.

[vjaneczko]

Sounds like your O2 sensors are failing; at least the front one for sure. The rear may be indicating the catalytic converter is on its way out, the rear sensor itself is on the way out, or it's being affected the front sensors' failure.

Read the "Automotive applications" and "Sensor failures" sections for a great understanding of what they're doing:
http://en.wikipedia.org/wiki/Oxygen_sensor

[john_dakins]

Thanks for the link, very informative. Even if that isn't the direct cause of my turbo issue, at 170K miles it makes sense to fix it.