2002 Explorer new (rebuilt engine) coding P0442

[McFudden]

So, long story short. I spun the bearings out in the desert (lucky me)... and went engine shopping. I found a shop that said they would install a rebuilt engine, with an unlimited mileage 6 year warranty. Sounds like just the deal for my lazy butt. I go, engine swap (new engine is leaking oil crank shaft and rear of oil pan, but that’s another issue) drive some driving, first oil change at 500 miles, and the service engine soon light comes on. P0442 is the code. It points to a small leak. Before I spun the bearings, hell even AFTER I spun the bearings, this explorer leaked NOTHING! No coolant leaks, no spots on the driveway, NOTHING! Now with the new (rebuilt engine) I’m suddenly getting this error. The shop is insisting I’ve spontaneously developed a fuel tank leak. I disagree. I say this is probably some vacuum hose they didn’t attach well and or cracked etc etc... anything else that they might have accidentally done swapping the engine that might be causing this? My explorer never smelled like gas before, and now it does.

 

[Turdle]

That code can be set by a leaking gas cap which could develop every time you fill the gas tank.

It could also be a leaking gas tank fill tube, or, a hose leaking. even if the shop induced it it was because the hoses were so old in the first place, let them fix it but don't expect free fix.

They should fix the leaking rear oil seal though.

 

[McFudden]

I honestly guessed it was the gas cap as I noticed really crappy gas mileage and put a locking gas cap on my explorer (think about it for a minute and figure out why I thought a locking cap would fix “crappy gas mileage,”) and then that code developed. I went back to the OG gas cap and a few weeks later it coded again. I am smelling gas fumes for sure, buuuuuuut I never smelled them on the old engine. Also, I’d say every 10 or so times when I try to fire it up it hesitates and I get vapor in the exhaust. Pair this with the fact that the just plain forgot to reattach the HVAC vacuum hose, that makes me think that maybe it’s not a tank leak, fill tube leak, gas cap issue, or cracked line, and that they maybe forgot to hook something up or seal something. (This is the second time I’ve had to bring it back to them because it’s leaking oil.). The new engine has less than 1000 miles on it because it’s spent a combined month in the shop.

 

[McFudden]

I should also mention the gas fumes seem to be coming from the front rather than the rear.

 

[imp]

I should also mention the gas fumes seem to be coming from the front rather than the rear.

@McFudden
And there lies the problem, probably. The "Evaporative System" is an additional "reservoir" which "stores" fuel VAPOR, not liquid gasoline. It consists of a cannister filled with charcoal, usually mounted up front somewhere, but not always. It is connected by hollow tubing, metal and rubber, to the fuel tank. Thus, the tank filler cap may be vapor-tight at all times, except when it is removed to fill the tank. A vapor pressure sensor is mounted (usually) near the tank, and provides an electrical output to the PCM (computer) telling it the pressure level. As the vapor storage cannister becomes saturated with trapped vapor, the pressure level is at some point released by diverting the fuel-containing vapor to the engine's fuel inlet system (fuel injectors), where it is burned in the engine.

When the evap system vapor pressure reaches the level where it must be released, a vacuum-operated valve is opened by the PCM via an electrical solenoid, allowing the built-up vapor to be destroyed by burning it in the engine. The whole purpose of all this is to maintain the entire fuel system, tank, fuel lines, all areas containing fuel, sealed from the atmosphere, thereby allowing NO VAPOR to escape.

There are numerous points where leakage may occur: Hose connections, cracked hoses, damaged cannister can, leaky diaphragm in the dump valve, tank filler cap, and so on. Your code is stating that vapor pressure is not building up as expected, due to a leak somewhere.

Trick is to find it......imp

 

[McFudden]

That’s I guess why I’m posting this. I’m not looking to blame the garage as a “so there!” thing. The garage has been surprisingly willing to help. The engine now has a 6 year unlimited mileage warranty, which is awesome. I’ve brought it back to them twice for the same oil leak they have yet to fix, but they’re still trying fix it and it’s not costing me anything. I’m more asking if anyone knows a common vacuum hose that might be overlooked. If I’m correct, I believe the evap canister is way up front and not near the gas tank because everything in the 2002 explorer seems to be more complex than it needs to be. As I previously stated they did manage to accidentally leave a vacuum hose of the HVAC (accidents happen and they were more than happy to correct it,) so I figured another mistake could have happened and I hoped someone else had experienced this on an engine swap and could offer “oh, sounds like they missed this. Have them check that out.” I could then pass on the knowledge to them. As I said I did swap the gas cap to a locking one and thought that might be the issue but I kept the OEM cap and have swapped back to it, AFTER I cleared the code.

 

[Drewmcg]

Can you get the garage to do a smoke test of EVAP system w/o charging you an arm and a leg? That should pinpoint the problem.

P0442 pretty common on '02s. Nothing to do with rebuilt engine, normally.

If a new gas cap doesn't take care of it, and there's no rodent problems noted, I'd suspect the filler neck. Do you have any problems filling the truck with gas (e.g., premature shutoff of pump)?

I've replaced my cap, fuel neck, and still have a P442 (though, thankfully, can fill the gas tank w/o delay now). But I know I had rodents chewing on the evap lines that lay on top of the tank. Someday I'll get around to fixing it, maybe (no annual inspections to worry about in Michigan).

 

[McFudden]

It’s about $100 to smoke it, which isn’t horrible. I’m not due for an inspection for awhile so I’m not in a hurry. Like I said, I had just hoped it might be something common someone could say, “oh yeah, it’s probably this.” I get that the EVAP system is anything but simple.