P0455 EVAP Large Leak: After Vapor Canister Solenoid replaced

[rogerranger2122]

anyone wanna take a crack at this?

2000 ford ranger 2 wheel drive 4.0 litre 6 cylinder 70,000 miles.


I originally had codes:
P1451 Evap Emessions Ctrl system vent Ctrl Cir
P0133 02 sensor Circuit Slow response bank 1 sensor 1
P0153 02 sensor circuit slow response bank 2 sensor 1
P0171 system too lean bank 1
P0174 System too lean bank 2
And no Pending codes.

I cleaned MAF sensor and the lean codes stayed gone after erasing all the codes with my code reader.
The 02 sensor codes went away also after I changed out all my 02s.
I replaced the Vapor Canister Solenoid and it cleared the p1451 code. I had no codes at this point but I had EVAP wasn't "ready" but still managed to pass NJ inspection like that. I'm good on inspection for a couple years but want to fix the problems I have now.

Now I have P0455 Evaporative Emessions System Leak Detected (Large Leak).
And the P0171 and P0174 are back.
no pending codes. EVAP and all systems are "ready".

The lean codes, I dunno, I gotta do some more tinkering. I already sprayed carb cleaner near the intake manifold and heard no change in rpms indicating a leaky gasket but that's not a %100 gasket test. I did a few other tests at the time but didn't check the idle air controll valve. Maybe I just need to clean my MAF sensor again AND change the air filter instead of just brushing it off. Possibly change the fuel filter as well. I dunno but it is very noticably running lean, the truck rumbles when first started up as if it's going to stall. It's been like that for the 2.5 years I've had it. In winter it sometimes stalls out when I come to a first stop.

I'm asking about the EVAP code. I never had that code until AFTER I changed the charcoal Vapor Canister Solenoid. Do you think I should change the whole canister, and/or the EVAP purge valve? One good clue I think is that when I'm almost out of gas and filling up, the gas station's hose shuts off as if the tank is full. The guy there said it's because there's air backed up in the tank system. I still have to check all the rubber lines for the evap system but I'm thinking they'll be ok. I changed out the fuel filler neck where the gas lines connect before I had all the first set of codes (and connected them tightly with hose clamps so I don't think it's the filler neck), and I just got a new gas tank cap. I didn't install the gas tank cap yet though but I doubt it's that because of the gas station pump triggering full (from air) when the tank has no gas.

 

[RonD]

EVAP system uses engine vacuum to suck air out of the gas tank, when engine is running of course, there is an EVAP pressure sensor and an EVAP solenoid in the engine bay, between engine intake and Canister
Computer opens solenoid then monitors vacuum pressure via the sensor, the canister and gas tank are one sealed unit, or should be, so vacuum pressure will build up a bit, and computer starts to Pulse 12volts to solenoid, this keeps vacuum pressure low so fuel pump can still pump gasoline out to engine.
If canister or gas tank can not build up a vacuum then there is a leak, could also be in solenoid or sensor hose, or even a bad sensor or solenoid(not opening)
Hose from canister to gas tank is long but usually doesn't fail, usually is not never though.

The bed to gas tank, the filler and VENT tubes are metal and rubber, and do rust or crack, so that is a common EVAP large leak code maker.
The vent hose lets air out while you fill the tank, it runs next to the larger filler hose and air vents out at filler neck, gas cap seals filler and vent holes
Look from under the bed and you will see these hoses.
Gas Pump shutting off while filling tank usually means vent is clogged, or filler neck is, gas is backing up in neck.

EVAP system isn't the "vent" used when filling the tank, it is an emissions system, it does keep tank sealed when truck is parked, this is why you often hear a hissing sound when removing the gas cap to fill up.
Engine was just shut off so EVAP still has tank sealed with negative pressure, if you haven't heard that sound in awhile then check filler and vent hoses


The lean codes do not mean the engine is running Lean.
The computer gets MAF air flow data, then calculates the fuel needed for the 14.7:1 air:fuel ratio for that amount of air.
This calculation is 0 fuel trim
After fuel is burned O2 sensor tells computer if burn was good or too Rich or too Lean
If Lean computer adds more fuel, this happens in less than 1 second, more fuel is +1 fuel trim, if more is needed then +2, and +3 and +4, ect.............
If fuel trim gets to about +20 then computer will set Lean code, -20 would be Rich code.
The extra fuel is being added so engine is not running Lean.
The CEL(check engine light) and Codes are to let driver know that there is a problem with computers 0 fuel trim calculation.
For both banks to have Lean codes then it wouldn't be O2 sensor issue as that would only effect 1 bank
MAF sensor would effect both banks
Low fuel pressure would effect both banks, computer doesn't have a fuel pressure sensor, in 2000 model it expects 65psi, if pressure was 45psi then computer would have to add more fuel because less is flowing in when injector opens.

Upper intake manifold vacuum leak would effect both banks
If the air tube from MAF sensor to Intake manifold had a leak then that would effect both banks.
MAF system only works if ALL the air going into the engine passes thru the MAF sensor

The EVAP system gets its vacuum from upper intake, so..............vacuum leak in that hose would effect fuel trims and EVAP system

Rough running and stalling could also be vacuum leak issue

After engine is warmed up and idling, unplug the wires on the IAC(idle air control) Valve, RPMs should drop to 500 or engine may even stall, either is good, it means no vacuum leaks.
If RPMs stay 700 or higher then there is a leak.
At this time unhook 1 intake vacuum hose at a time and plug port with your finger, see if you can find the upper manifold leak.
RPMs would drop to 500 or lower when leak is plugged

 

[ratdude747]

I'd check all of your connections. I know the one time I forgot to hook the canister hose to my intake, my engine would race and then die due to the resulting massive vacuum leak. It isn't hard to accidentally unplug a hose during that job... from the intake to the canister I'd follow the line and look for obvious leaks as a first step.