Recently my check engine light has been coming on and off. I have read all the other threads and have not seen my symptom... after I fill the tank, the light goes off and stays off while driving until the tank is 3/4 full. Then as soon as athe gas uage needle gets to the 3/4 mark it comes back on and stays on until it is filled again. The light does not go right out when the tank is filled, but after a couple of short trips, the light will go off. Any ideas?

 

o2 sensors.

 

Pick up an inexpensive code scanner at Harbor Freight. Read the codes and post here for diagnosis. That's much cheaper than throwing parts at the problem.

 

is probably going out,but is remaining as pending stored in the ecu until the next time it trips completely and goes to an active check engine light.
Harbor freight tools has the 94169 obd2 scanner on sale for 40 bucks right now.Or go to shucks or kraggens when the light is on and they will read the codes for free.Just write down the codes not what they tell you they think it might be.
post them when you got em
ohlord

 

Thanks for the advice, as luck would have it the light went out this morning at about half full. When it comes on again I will have it checked and let you know.

I noticed that the gas I buy at Getty in NJ, 93 octang, contains 10% ethanol. Does all gas contain ethanol now and could this screw up my engine?

 

or changes in labeling laws now require it.The codes should still be stored as pending even thought the light shut off.