I have a 2000 3.8l mustang. It has a check engine light and the code is p0455(small evap leak). It smells like gas and gets 250 miles on a full 15 gallon tank(roughly 15mpg). I know that to fix the gas smell I prolly have to change the header gaskets out. Here is the fun part:
The drivers side spark plugs are all rich(black) and the passenger side spark plugs are all lean(red). I need to know how to test my 02 sensors without a scan-tool. And what is the easiest way to change out my oilpan gasket without removing the cross-member. I also have a ticking sound, but that's probably just the gasket on the headers needing to be replaced. I have some hand tools, a jack and jack stands, that's about it. Can I do this myself or do I have to take it in to fix it?

 

p0455 is not a small evap leak, it is a large evap leak:

P0455 - Evaporative Emission Control System Leak Detected (no purge flow or large leak)

Most common cause is a the gas cap not sealing properly. Other then that, its a leaky hose in the evap system. It would explain the gas smell.

 

^^^agreed..

 

I would agree with you except that I have had the DTC for about 8 months and the gas smell didn't start until a couple weeks ago. I would understand a hose coming loose or cracking and creating a leak, but wouldn't it start out as a small leak? And if it did start as a large leak, wouldn't I have smelled gas sooner?

 

Well the black plugs means really rich so the fuel smell is likely unburnt fuel from that side. If you have a garage and tall jackstands you should be able to manage the work yourself. Buy a haynes manual so you can see what you're up against and just replace all the 02 sensors then you cam rule them out as faulty and you can guarantee proper mileage and such because my gt gets better fuel economy then that bro so something is definitely wrong

 

Not necessarily. 'Large' is relative to the system. The EVAP system is fairly small.


Agreed. However, the plugs may not be the cause. They may be the effect. If something is fouling the plugs (e.g. oil/coolant leak into the cylinders) or the plugs aren't getting enough juice to generate an adequate spark, they won't burn the gas as efficiently and you'll get a rich condition.


Thats a pretty expensive guess to blindly replace all the O2 sensors ($50 x 4).

 

If you are unsure and don't have much in the way in parts/tools to chase the problem yourself take it to a shop. If you have friend(s) that have a buddy who works or has a shop to get a free/discount that would be nice. Other than that, bite the bullet and get a shop to look at it.
I had a bad miss on #2 cylinder, shop wanted $600 just to take the head off no repairs to investigate. This was after I checked plugs, wires, and they rechecked them and the coil and injectors. Fixed it myself, broken spring no head removal, for $350 (tools rental and part).
Have them find the problem and fix it yourself for cheaper.

 

Check you fuel filler neck tube seal where it meets the gas tank, mine was rotted out and spilled out gas everytime I made a left turn with more than a quarter tank of gas. Got the same code, fixed it.

 

15 dollar part and took 35 mins to fix without dropping the tank

 

Now if I can figure out why my steering wheel won't return to center on its own after cornering and fix a small exhaust leak that I've yet to pinpoint(think its just gasket) ill be golden lol