1993 Mercury Sable MAF sensor

1993 MERCURY SABLE
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MJM4310
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I have a 1993 Mercury Sable 3.8 liter V-6 auto transmission with about 106,000 miles on it. The check engine light came on while coasting down hill around 35-55 mph. but went off right when i gave it gas. So when I got home I put the EEC-IV Diagnostic Trouble code check on it and got a trouble code 157 Manifold Air Flow Sensor Fault (Low Voltage) and 628 Excessive Converter Clutch Slippage. So I purchased a new MAF Sensor and put it on and the car ran well didn't have a rough idle had power and ran well. Now about five days later i was going down a fairly long hill coasting 45 mph and check engine light came on then right when i gave it gas it went off. So I tested it again and got the same codes. Now i'm puzzled I don't know what to do. If any one has any information at all for me it would be greatly appreciated.
Thanks alot.
Mike
Jan 16, 2006 at 10:06 AM
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DARRYL
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Hmmm? strange indeed. Well the MAf sensor monitors air flow through the intake manifold via the throttle body. The more air the more voltage to the ECm so it knows that more fuel is to be added. If you are coasting down a hill i assume your foot is off the throttle, this will cut air flow to a minimum and the output voltage should drop decreasing fuel supply. Now what if the TCC clutch is still locked up in the converter for some reason causing the car weight to now drive the engine (like a standard shift would do). Now the engine is trying to suck a lot of air through the throttle body which is closed because you are coasting. Well the MAF voltage might be wrong for the condition of the other sensors, like TPS (throttle position sensor). So the computer wants to know why one sensor says one thing and the other says another thing and it gets confused. So i wonder if you don't have a torque converter issue on your automatic transmission. Try shoving it into neutral the next coast down a hill. If the car is driving the engine is the only thing that comes to mind because of the slippage error you got???
good luck
Darryl....
Jan 16, 2006 at 9:41 PM