What is the deal with the check engine light? I have a 1997 Expedition with the 4.6. Around 58,000 miles the check engine light started coming on randomly. No decline in performance or engine operation that I could tell. I was told to replace the gas cap. No luck. The code is P0446, and has to do with the evaporative emissions system. I know there are at least two sensors and a solenoid involved with this system and I was wondering if anyone else has had this problem. I have a code reader and it comes up with the same code each time I check it. When I shut off the light, it may come on later that day or not for another week. It's totally random. The new gas cap does not seem to fit any tighter than the old one and I am wondering if there is a better way to fix that. I have a friend with and F-150 and the same engine. He has had the same problem with the same code. The dealer says I have a vacum leak somewhere in the tubing that runs to the charcoal canister. Good luck finding that. Help!!!!!!!!!!!!!

 

Same problem with my 97 Ford F150. Light would come on and off intermittantly. Tryed changing the gas cap with no success. It ended up being the charcoal canister which is located above the rear axle on the F150. Relativly simple to change.

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1997 F150 EXtended Cab 4X4. 4.6L. 3.55 with tow package. K&N Filter. Flowmaster Delta 50 with dual exhaust out the back and 3.5 inch tips. Kenwood CD player.

 

Thanks for the info. I wondered if that might be it or not. Did you have a leak in the canister or was it the sensor on the canister giving you the trouble? I was told by a mechanic at Pep Boys that over filling the fuel tank can cause a failure of the charcoal canister by allowing liquid fuel instead of just fuel vapor into the canister.