Scanner reads this code P0172 as #1 bank too rich-which I read as there's too much gass in the system-where do I start. Do I pull the plugs to see if they are wet-what else will cause this-if the 02 sensor was causing the richness in fuel-would not the scanner say 02 sensor?
Thanks to all who answer.
Poolman

If it's only on one bank (and at the moment I can't remember how the ECM can detect differences between banks), it could be a faulty injector. or a vacuum leak. An injector could be hanging up spraying too much fuel, or conversely too little fuel or if too much air is getting into the system (from a vacuum leak) it will richen up to compensate. My Volvo ECM book is on the Motronic 1.8 system. Someone with the 4.4 book can be more accurate.

Let us know what you find out Poolman.

DEWFPO
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1998 S90 071,245 and 1995 964 154,100

My interpretation of that code is that based on the O2 sensor output signal the system is having to excessively and constantly adjust the gross mixture towards lean. It would not be an O2 sensor problem as the ECM must be receiving a valid bouncing signal from the O2 sensor. If that signal was not bouncing (ie always high , low or in the middle) you then would get an O2 sensor code.

When running slightly rich the plugs would not be wet, that happens on a no start with no spark.

I would guess at fuel pressure regulator or MAF sensor based on my experience with the older LH systems in 240 and 740 cars. I believe there is a mixture adjustment on the MAF but not sure.
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David Hunter

I found the problem and it is -ME-got my new purge valve in from Grotten last night -changed the part over and some how had pulled the vacuum hose off from it's mount that goes to the heater and asessories. Dewfpo's right on ,vacuum leak big time- I'm the dummy here
Still don't understand how this OB11 system doesn't reset like it's supposed to,
David, you stated there has to be a set # of miles recorded before the system sets itself back-do you know the number of miles and at whatever intervals they are supposed to be.
Thanks for the responces Guys
Poolman

Poolman,

Glad you found the problem and it was an easy one, no $ involved.

On our 98 S90, when I repaired the PNP sensor a few years ago it took 3 complete, cold startup, run and cool down cycles with no codes generated for the OBDII system to reset the check engine light.

DEWFPO

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1998 S90 071,245 and 1995 964 154,100

Thanks Dewfpo-I reset the code with my new toy(actron scanner) and the light is off now. What I'm trying to figure is the ready and not ready codes from the emission system-this is the same thing that Lawunion is batteling in one of the posts below. The ignition, fuel and compression codes all read ready but the rest of the codes 02 sensor h02 sensor cat and egr (which there isn't one on this model) along with the air pump all read not ready. Now I don't have to contend with the state of Va on emmisions on these points like Lawunion does,but I'd just bet that some where in the middle of all this is the 3-or 4 miles to the gallon thats been missing. I don't know if the purge valve could have caused the problem but will be checking in the future for sure.
Thanks Poolman

Make sure your thermostat is working correctly. I've, several times now, had mine fail by over cooling the engie and the milage went in the toilet.

I now keep an eye on the temperature gauge and if it doesn't come up to 1/2 scale within a couple miles of starting I begin to suspect the thermostat again. I've been getting them from the dealer but even so they seem to have a short life.
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'96 965, 16' wheels, Michelin Pilot Sports, rear 18mm bar + Koni, 201 HP cams, 132K. Put 200K on '85 745 TD.

Thanks Jbowers,I'll change her out-been a couple of years at least since a thermostat was changed in the car. Will post back if that was or was not the cure.
Oddly enough I thought and stated not long ago the car was getting better gas mileage in hotter weather-you may have just hit the nail on the head.
Thanks
Poolman