'94 Mustang check engine light

I have a '94 Mustang with the 3.8 engine that was rebuilt 25 000 miles ago. Idles smooth, starts great and has no hesitation. Everything is as it should
be. A month ago I filled it at a gas station I usually don't go to and after about 1/8 of a tank being burned the check engine light came on. I checked all the hoses, wires, basically everything I could put my hands on and it all seems ok. I disconnected the battery and reset the computer and it was fine. A few days ago I again filled the tank at the same station because it was the only one open locally and the next day the check engine light again came on. I thought maybe it's some bad gas or something similar. Then the next day when I started the car a huge cloud of white smoke came out the back for about 5 seconds or so. I know white smoke usually means water and coolant is being burned but the coolant level is up and hasn't dropped one bit. I'm not losing oil, coolant or anything. I even took out the MAF sensor and sprayed it a couple of time with an electrical contact cleaner I bought specifically for electronics and contacts. It looked like new before and after I sprayed it, not covered in any gunk at all. My guess is water in the tank but I'm not too good at troubleshooting this kind of stuff.
I'm taking it into a garage to get the diagnostics read but I was wondering if anyone has any ideas what it could be.
Thanks for any and all input or ideas!
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How white? steam white or oil white?
Don't go to that gas station again!
There is a way to pump out gasoline into a jar and see if you have water in the gas, but it is quite dangerous to do this, need long hose, probably two people, etc. If so, you can get rid of the bad gas in a few ways.
I got a load of water at a station when they were refilling from a big tanker, Car would run extremely rough, must have mixed up the water at the bottom of the gas station gas tank. I pumped out about quart from the fuel line and it had a about 1/4 cup of water on the bottom of the glass jar, so I pumped out about two gallons into another tank, and put in some ethanol a pint to help dissolve the water some. Car ran great after I got rid of that tank of gas. Bad Gas. The fuel pump is located at the bottom of the tank so it can pump out the water as water sinks to the bottom quickly. Never went back to that gas station.
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I'm staying away from that station like the plague. It's a busy station so I thought the gas would be no problem. If it was oil white or steam white, I'm not sure. I thought there was slight smell of oil but I didn't expect that to happen and it might have been exhaust I smelled. I've started it a few times since and no smoke, everything is fine except for the check engine light is still on.
I have another question...if the check engine light comes on and the problem is fixed, will the light stay on until the computer is reset or will it go off when the problem is resolved?
The idle, coolant levels and everything seem ok, so I'm starting to think it was the gas station and their gas. Too much of a coincidence to suddenly happen like it did.
Thanks!

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The light should go off when the condition that caused it is resolved. An error code is stored in the ECM until it is reset. The codes can be retrieved, most service manuals will detail how.
rd
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wrote:

you can read them out with a meter, or have a service station do it (they like $75)
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Thanks for all the info. I don't suppose that a meter to read them could be bought at any auto supply store? I'd be tempted to buy one if it could be used on other cars as I'll probably always be driving and fixing something. Is it an expensive piece of gear that someone like a dealership or other repair place would have?
Thanks again.
wrote:

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at 24 Aug 2007, exacto [ snipped-for-privacy@hotmail.com] wrote in

If you have an Autozone nearby, they will generally connect a meter and read the codes for you with no charge. Both for OBD-I and OBD-II. My old 3.8 95 Stang had OBD-II. Not sure about the 94, it could be either.
OBD-II reader go from around $80 to several 1000's. Depending on their complexity. You can get a unit for about $150 that will connect to your home computer and give you loads of info. May be worth the investment if you intend to do work on your car.
Good luck!
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