the signal lights on my niece's 1990 sundance quit working,we have replaced every bulb and the flasher but stiil they don't blink,the four ways work and all lights work on signals when you move lever up an down or turn on lights they just won't blink even tried diff flasher thinking this one might be faulty Any ideas????

2002 Ford Taurus 3.0L flex fuel engine. I'm going out to get more information in a little bit but here is what I have so far. My parents are down from the north and have been running E85 exclusively for a while. On this trip they have been using 'regular' gas. Emission light came on when they got here but we were on the way 2 hrs down the road. Engine stumbled a little at idle and a slight miss from time to time but otherwise ok. Got back yesterday, I hooked up my scan tool and found P0172 and P0175 (fuel trim system rich bank 1 and 2). I'm thinking MAF or MAP (whatever it is) since it set both codes at once so I sprayed some cleaner on the sensor wires. Air filter is new. Light stayed off in the driveway, I put it in reverse and it came on and is still on but I haven't hooked it back up yet. Are there any readings I can provide to help diagnose this problem? I don't want them to get down the road into a 13 hour trip home and something fail.