Hello,
I have a 1994 Dodge Intrepid, 3.3L flex fuel, with ~240,000 miles.
The car displays an intermittent code 51, "displays lean mixture".
The car starts and runs well.After theenginewarms up,you'll be driving on a level surface OK (not accel. or decel.), but as soon as you either let up on the gas pedal or "feather" the gas pedal, at some point in time the check engine light will come on on the instrument panel and a code 51 will lock into the computer.
Here's the best part.... at some point later in the trip the check engine light may go out, then later come on again.
Andat any point in thetrip,if theignition is turned off, even if the engine is immediatly started again, the check engine light goes out.
I've replaced both oxygen sensors, the most common cause of a code 51. There is 12 vdc supplied to the oxygen heaters. I've replaced the PCV valve, and there is a vacuum present at the valve. I cant hear any vacuum leaks under the hood.
The Dodge service manual says to next drain the tank and change the filter, but I don't experience any stumbling, etc. normally accompanying a fuel related problem.
Does anyone have any idea what to check next? This has been going on for months now.
Thanks in advance for your input.

 

I forgot to add....
My gas mileage has gone down from 24 city / 30 hwy, to 16 in the city.
I understand that if the computer thinks the engine is running lean, it will cause the injectors to run excessivly "fat" and therefore decrease the miles per gallon.
Thanks,

 

There is no way the light should reset within a trip, unless the code is a false trip (aka bad computer). Well, also if the battery is disconnected for a few minuets. In any case, I think there is something wrong with your PCM.