mark '87 930

When I changed out my headers a few months ago, I fried my O2 sensor by heating it cherry red to remove it from my stock headers (live and learn I guess). I only realized this as the car was running like crap when I gave 'er lots of throttle, and it was worse under boost (major black smoke out the back).
I replaced it and the car was running well for awhile. Lately though, I noticed the same symptoms, when I hit the gas, esepcially under load (3rd or 4th gear), the car just doesn't go anywhere. It seems to be only when the car is not completely up to temperature yet. The boost gauge registers, but the car just doesn't move. If I disconnect the O2 sensor, the car no longer bogs down and the problem goes away. As a result disconnecting it though, my idle is rough and low, as well as the power to 3K RPM just isn't smooth anymore.

Tonight I verified the O2 sensor with voltage and it seems it go from .1 to .85 roughly which seems to be within spec. I also tested the O2 connector going to the module by grounding the no.1 pin to the negative battery terminal, and that tested out ok (RPMs went up as did the O2 sensor voltage reading).

I guess I don't need the O2 sensor, but I like the smoothness of the car with it connected.

Help, what next? A relay under the drivers seat? Get a meter to verify the frequency valve?

A930Rocket

I think everyone has the O2 sensor removed and the CO set at 3%. Check the usual stuff like cap, rotor, plugs, wires, timing, etc.

mark '87 930

I'm actually about to do a full tune up.. I figured that when the O2 failed last time, it was so rich that I fouled up some plugs... I just don't want to put new ones in and foul those as well!

nathanUK '81 930 G50

Remove the sensor and set the CO before you change the plugs. You can always check the CO afterwards as well.

mark '87 930

How do I set the CO? I need that dwell meter don't I?

nathanUK '81 930 G50

The CO refers to fuel mixture setting at idle. AFR at idle at 3%CO is 13.38 AFR

http://www.perfectpower.com/technical_info/afr.asp

You will need to take it to a garage/emission tester.

Or buy a AFR gauge or buy a Gunsons gastester if you want to get your hands dirty

It has nothing to do with dwell.

mark '87 930

Would I be able to possible use the voltage I get from the O2 sensor (assuming my O2 sensor is functional). I thought the voltage of the O2 sensor corresponds to a A/F mixture? correct me if I'm wrong, I thought I saw a chart somewhere that says compares voltages to A/f ratios.. somethign like .6V si the figure?

i also presume that the only adjustment I have is the infamous 3M allen screw?

nathanUK '81 930 G50

I think the stock sensor is only for measuring 0% CO. Any other reading (voltage) will just be an indication, not a measurement. Basically it will say whether the CO is out or not from 0% and which way it is out (rich or lean).

Correct me if I am wrong guys.

EDIT: That chart you posted pretty much confirms what I am saying. Temperature is more of a factor than the CO to try and get 3% CO.