I just gave my recently purchased '98 S70 GLT w/ 84000 miles a tuneup (plugs, cap, rotor, fuel filter) and I am still getting terrible fuel economy (about 10-12 MPG city, not really driving fast). However there are no other problems with the way the car is running; performance seems OK, no rough idle, engine fires up instantly, and no service engine lights or any others lighting up. The only thing that I can tell might be wrong (other than the crappy mileage) is that the exhaust seems to have a strong gasoline odor (it's not the gas tank because I don't smell it when the engine isn't running) indicating, I guess, that something is causing a rich mixture. Does anyone know what would be doing this, how to remedy it, and how bad for my engine, catalytic converter or whatever running it in this condition is? Thanks. Steve

After doing a some research (thanks for the info, bl) I thought that my problem was most likely a vacuum leak (I haven't had the codes read since I had no CLE) and set about checking the rubber vacuum elbows. I started by removing the battery and tray and looking at the vacuum pump. I didn't notice any damaged lines, however I notice that there was a larger fitting on the pump which had one smaller line connected to it which was wide open...I looked around for a loose hose, none to be found and then for a plug, again none to be found. Does anybody know if this is by design...if this part of the vacuum pump is supposed to be open like this? Next I went to the elbow on the right side of the intake manifold (looking from the front). While trying to remove the elbow I broke the plastic hose inside the foam insulation. Looking inside the engine I saw the end that had been broken under the space between the first and second pipes (from the left) of the intake manifold. How difficult is it to remove the intake manifold on this engine? Am I risking serious engine damage by running the car with this vacuum line disconnected? Any help that anyone can provide would be greatly appreciated.

A good bet is one or both of your O2 sensors are failing. They will eventually turn on the CE light but not necessarly while they are in the process of going bad. The front (pre-cat) sensor sets your fuel mixture. Another possibility is that you knocked off a vacuum line somewhere when changing components or have a vacuum leak elsewhere. Bay 13 gives you the most common locations to look for leaks. A vacuum leak will fool an otherwise good O2 sensor into "thinking" the mixture is too lean and it will enrich it to compensate. Just went thru a similiar situation with our 96 850. Car ran fine but was getting about 12 mpg and the exhaust fumes would water your eyes.

bl