1999 ford Taurus was run out of gas Ran rough. We added a gas treatment to take care of moisture or sediment in the gas and that is much better but now the idle stays up about about 2000 rpm at idle i
Unfortunately their are several possibilities when it comes to gas problems. If it's doing better now then maybe you can rule some out but for sure I would suggest changing the gas filter. Some pull the fuel relay switch while car is running then let it die on it's own to use up some of the fuel in the line, disconnect the battery, then pop the clips on the fuel filters lines with a screwdriver, be careful when you pull the hoses as some gas may still come out, then swap the filter. Could also be the fuel pump, one indication of this would be if you've had some rough starts, not hearing the pump prime, or had to give gas when idling. It is actually not the worst job to replace the fuel pump, some offer lifetime warranties for around $142 if you can do your own labor but suggest two people to help get tank out then back in right place, several hoses and some electrical to disconnect, need extra jacks if doing at home, line straps back up correctly and have patience when adjusting in place, also, don't pinch your electric near fuel filter if replacing pump, go ahead and plug it back in before setting the tank back in. Other possibilities are vacuum line problems, everybody says the pcv elbow first but I disagree, that depends on the model, for tauruses, there is a smaller one at back of engine that tends to melt or brittle in spots and break, rectangular sits on one or two lines at bottom and pushes in sideways, not so easy to find replacement because many car parts places don't carry in store, can snag at junkyard. If it is starting to break but not all the way through, will notice problem more in low speeds than on highway. MAF sensor may needed cleaned, vaccuum line coming off MAF sensor going in to engine could be loose, fyi, it pushes in at both ends, throttle not usually an issue, water leaking on O2 sensors could irritate them, O2 sensors don't usually go bad as often as they code and can be cleaned by soaking in gas, EGR valve could be clogged, would try this last as is difficult to remove and don't want to bust pipe getting loose. Also, if misfiring, may need new coil pack or may simply need to check and clean your spark plugs. There is also electrical at the funnel but not typical. Good luck, hope you get it narrowed down.