Hey i have a 2001 Mercury Sable Wagon. The other day it was running fine and over night ( 12 degree cold ) the next morning within 5 mins of driving it the engine lights starts flashing on and off. The Engine started to feel very rough and truck like. I think it might be due to my tank only being at half a quarter. My gas needle is always confusing, because it said i had a quarter left and then in the morning it was only at a half quarter.I filled the tank up to full because my dad and friend said it could be because of the gas to water ratio but wouldn't it be getting better now that i filled my tank all the way?? How can i fix this problem??

- Thank you
Chelsea

 

Hi Chelsea:

You had what's called a rough idling and rough running engine. There was missfiring all over the RPM range. When the engine misfires as bad as yours there is a lot of unburned fuel going into the catalytic converter. The converter burns off the excess fuel in order to save the planet. The light was blinking because there was way too much fuel and the converter could melt down costing you lots of money.
Don't drive with the CEL flashing.
Misfires could be caused by:
*bad ignition parts: spark plugs, wires and coilpack burn out over time. Your car is 12 years old and probably has more than 100 000 miles on it. If these parts haven't been changed recently they are due now.
*Fuel related problems: I doubt there is a water issue. Today's fuels contain so much ehtanol that any potential water is removed. Also, we are talking too much fuel not too little. So I don't expect a clogged filter either.
Some fuel injectors might be stuck open and flood the engine. A "Seafoam" treatment might help in that situation.
*air supply: Too little air has similar effects as too much fuel. Is the air filter dirty? It needs to be replaced now and then.
Vacuum leaks could cause misfires. Make sure all hoses are connected and have no holes or crack in them: vacuum lines, brake booster hose, PCV hose and valve grommets.

You could do the above checks and replacements if they haven't been done in a long time. But there is a chance that the problem is somewhere else. If you want a bit more confidence you could go to a parts store and have them read the OBDII codes. They do that for free. Report the codes to us.