I have a 1999 F-150 and for the first time I failed emissions. I then brought the truck home and began replacing the problems according to the error codes; I replaced the CO2 sensors, I replaced the evaporator canister along with the valves both front and back. I still have an emissions light on. I had the light reset to see if that was the problem but each time it comes back on. What could I be missing or could I do to fix this issue and pass emissions?
I would really appreciate some help with this one. Thanks and Best wishes for the new year.
Hmm, something like O2 sensor lean codes and EVAP purge flow codes could both easily be caused by a loose or broken vacuum hose.
There are no codes that tell you to replace O2 sensors or EVAP canister or valves. Please determine the codes you have, identify the system that is malfunctioning, and with the aid of a service manual or repair information begin testing.
I think you mean “O2 sensors” rather than “CO2 sensors”. As said above, even if a code refers to the O2 sensors, that doesn’t necessarily mean there is something wrong w/them. It just means there is a fuel/air mixture problem of some sort. The problems could be any from among vacuum leaks, fuel pressure problems, clogged air or fuel filters, ignition system on the fritz, catalytic converter problems, etc. Oh, it could be O2 sensors on the fritz too. Since you replaced them, at least you know you have new ones in there I guess.
This is a situation where having an experienced mechanic and the specific scan tool for the vehicle is the best approach. Absent that, first thing I’d do is bring all the routine maintenance up to date, then install new air and fuel filters, and check all the vacuum controlled devices and associated hoses for leaks. Next I’d test the EGR. And the PCV. No go? Next would be a fuel pressure test. And a cat back pressure test.
If you Google “How to pass an emissions test”, there’s some useful info there.