Can someone PLEASE tell me wher to start looking to reamedy this code.I have already replaced fuel cap and reset computer several times.I am open to any suggestions

 

PO446 is Evaporative Emission Control System Vent Control Circuit Malfunction. This system traps and stores fuel vapors that evaporate from the fuel tank, throttle body, and intake manifold during non-operation or idiling, stores them in the charcoal canister and then routes them into the combustion chamber to be burned when the engine ir running. you could have a cloged canister,bad VMV fuel vapor management valve,fuel tank pressure sensor, fuel vapor valve or a cracked or split vacuum line that is part of the system. I would start with the vacuum lines starting at the canister. Repair or replace as necessary. If the canister is cracked or damaged replace it. The rest of the system, valves and sensors require some expertiese. Hope this points you in the right direction.

 

George is correct except I would start with the gas cap. A faulty or missing cap could cause this code. Think back and try to remember if maybe you left the cap off or loose one time when you got gas. My advice would be to clear the code and see if it comes back and if it doesn't I would assume the gas cap got left loose.

 

Thanks Guys,I have gotten more info from yall in one day than I did from any of my local Ford dealers in the last 3 weeks.Thanks mxracer and yes I did replace the gas cap and cleared out code and it was back within 3 days and I am going to try the other things that George suggested this weekend. Thanks Again
Shane Thompson

 

ummm...mxracer514 is a Ford Tech......

 

About 90% of the time its gas cap related but if you can't find any leaks at hoses or fittings my next suggestion would be to replace the canister purge valve also look at your canister if its got fuel in it theres your problem. There is quite a few things that can cause this. Most Dealers have equipment that pressurizes the evap system with argon gas and ck it with a leak detecter. leaks can be so small that you can't find them with the naked eye.

AJ (l) !!!!

 

The gas cap being loose or left off usually generates a P0440 code. And sometimes the P0441 is related to gas cap but P0446 is definately the evap cannister. Just a small leak can trigger it. We have a pressure tester that can pin-point the leak where i work (Lexus).If you can get the original DTC cleared, drive the vehicle twice for about 20 minutes ( two trip logic) and the code should reappear. I'll check back Friday from the shop and see how you are doing. Good Luck!.

 

Nope, ONLY a Probe can have a P0440 in 1997. No ford can have a P0441, and a P0446 has NOTHING to do with a leak. No fuel cap, or leaky hose or cannister can set this code. You guys need to do more homework before suggesting something like this. You're gonna have this poor guy looking for a leak when a leak can't cause this code.

Continuous Memory Diagnostic Trouble Code (DTC) P0446 or P1450 indicates that Self-Test has detected the Evaporative Emission Control System has excessive fuel tank vacuum. Also, a DTC P0446 indicates a vent control malfunction.

And while im not there to put my hands on it, I will say that in a 97 Expedition, most of the time this code is caused by a Cannister Vent Valve that is clogged with dirt, or something like a spider web.

What you can do to verify this condition, is to use a NGS or WDS to monitor the FTP, EVAPCV, IAC, EVAPPDC pids. Turn active command on, and set the IAC to about 60%, then set EVAPCV to 100% and EVAPPDC to 100% until the FTP voltage goes from about 2.4V to .35V. Then set the EVAPPDC back to 0%, and make sure the FTP voltage stays below half a volt. If it does, then set the EVAPCV to 0% and if the FTP voltage doesnt rise back over 2Volts, you have either a stuck Canniseter Vent Valve or a Stuck FTP sensor. Pop the gas cap off, and if the FTP suddenly rises back over 2V then, its a clogged Cann. Vent Valve. If the FTP voltage doesnt jump up when you pop the cap off, you have a bad FTP sensor.

 

I thought all emmissions related equipment was covered under a special 100,000 mile warranty?

 

Jeffflaws you are exactly correct, the gas cap has nothing to do with code p0446, I quess I shouldn't trust my memory when it comes to fault codes and a p0440 is a probe only code in 1997.

Ford warranty covers certain emmissions parts for 8/80,000, but if memory serves me correctly which is doesn't always in 1997 it was 5/50,000

After further review I agree with the clogged vent valve.

 

9E616 (converter assy) and 12A650 (processor) are the only thing covered for 8/80. Everything else emission related has only been 3/36 ever since 1995. In 94 and earlier, most of the emission components was covered 4/50 (i think that used to be referred to as S07).

Actually, did you know that federal emissions performance (non cali emissions) is only covered for 2/24! That means that if the check engine light isn't on, and you fail emissions at say, 29,000 miles, its not a warranty concern.

 

Sorry about that. Just passing on info from the book my scanner came with.
Jefflaws most of us do not have the equipment to conduct the test you are suggesting. In the event this shows up is there a simple method to diagnose which component is malfuncting. Cheere

 

Nope, but thats why i preach to people around here that call me at work and ask me what to buy when they are standing at a autozone parts counter. We regularly get people that spend a hundred dollars or so trying stuff before they come pay me the 49.00 to give them a guaranteed diagnosis.

 

kidtriton,
you had mentioned that we could call you at work and get the right info on ford related maintenance. can i call you at work? i got the same code coming up with my 99 expy. i read all that you wrote out but it is all to much for me to follow. any way you could help? thanks