My 850 NA is mostly short trips but after flooring it to enter an interstate,
the car had great pickup and threw the first code in months, 436.
"Front O2 sensor slow"
I reset the code and all is well around town again.

Is there a problem that the car doesn't want to rev up too much without
complaining?

Bill

I had this code recently and found it was my rear O2 sensor.

Read all about it here:
http://www.brickboard.com/AWD/index.htm?id=1459856&show_all=1


--
1998 V70 AWD->FWD Turbo 200k+

Thanks for that link to an interesting thread.
There was only a single code thrown and that was when I floored it onto I-95
No more codes with the usual around town slow speed stuff.
I'll measure the O2 sensor output soon, after I deal with the piles of snow here.
I wonder about the O2 sensor messing up gas mileage.

Bill

Your mileage and O2 sensor are messed up by using regular gasoline. Even using 89 octane will help.

If you were to fill up the tank with 18 gallons of gasoline, the difference between 87 and 91 octane is only $3.60. The higher grade of gasoline will up your MPG by 2-4.

Klaus
--
Always willing to listen, just not able to take direction.

Just a dirty O2 sensor from all of the low rpm driving.
--
Always willing to listen, just not able to take direction.

Will highway driving clean off that O2 sensor?

What impact does the O2 sensor condition have on around town mileage?

Happy new year Klaus, Thanks for all the help with getting this 850
back into good shape.

Bill

If the spark plugs are in good shape, you use premium gasoline, and the rpms are over 2000 for most of your driving, that should keep the O2 sensors reasonably clean. An Italian tune up might work, assuming there are no vacuum leaks, but the O2 sensor needs to get quite hot to start burning off any dirt.

Klaus
--
Always willing to listen, just not able to take direction.

I use the cheapskate gas, and whats the Italian tuneup?
:-)

Bill

The 5 cylinder engine in NA cars have a 10:1 compression ratio, it requires 91 octane. You can run with 89 octane if you do not floor the pedal.

The lower octane will set off the knock sensors, the knock sensors will tell the ECU to retard the timing and enrich the fuel/air mixture. The unburned gasoline will then coat the O2 sensor and lower your MPG.

An Italian tune up has nothing to do with Italians, unless they drive Ferraris. It is just a high rev, clean out the carbon, exercise for the engine. Usually lasting about 15 minutes in 2nd gear - keeping the rpms at 3000-5500 - with either the pedal floored or foot completely off. Fun! But watch out for the cops, not reccomended for freeways or residential areas.

Klaus
--
Always willing to listen, just not able to take direction.