Check Engine Light, Codes PO455 171 174

[REDDY]

when the check engine light is on, it stumbled a second when giving it gas, codes read lean, only acts up when lights comes on and did it twice now in the past month.

some solutions i heard so far:
o2sensor
gas cap

Any one know for sure? thanks

 

[REDDY]

when the check engine light is on, it stumbled a second when giving it gas, codes read lean, only acts up when lights comes on and did it twice now in the past month.

some solutions i heard so far:
o2sensor
gas cap
gas filter
Any one know for sure? thanks

??????????

 

[ERUSH97XLT]

Hi There,

P0455: Large EVAP Leak Detected
P0171: System Adaptive Fuel too Lean (1)
P0174: System Adaptive Fuel too Lean (2)

If all these codes are related, my guess is you might have a vacuum leak in one of your EVAP lines. This will explain all the codes.

If the P0455 is independent of the others, check your gas cap. If this is the case, you might be in a world of hurt with the lean codes. Those can be caused by anything fuel, ignition, or air related.

Let's hope the EVAP leak is causing a vacuum leak, thereby causing your lean codes.

Let me know if tightening your gas cap fixes the P0455 code. Do you have an aftermarket gas cap?

Good Luck,

ERUSH

 

[ThePhoenix]

can you explain the EVAP lines? where do I look...I am hoping its something OTHER than the the intake gaskets

 

[ERUSH97XLT]

Hi,

Your EVAP lines deliver fuel vapors from the fuel tank to the intake. It's a way to harvest usable fuel to aid in fuel economy and emissions (so I'm told by Ford). Basically, a canister collects fuel vapors from your gas tank, then purges so that your engine may use these extra vapors. The means by which your engine collects fuel vapors is by the natural vacuum which exists in your intake. If there is leak in the line somewhere, your engine draws in extra air instead of fuel vapor, causing your engine to think it's running lean and therefore overfuel. How's your fuel economy? Is it pretty poor?

The physical EVAP lines are pretty tiny. They run from your gas tank to below the battery (I think). In your engine compartment, they're tiny plastic tubes (tan in color?) that eventually lead to the intake plenum. If their is in fact a leak, good luck finding it; it's darn near a spaghetti soup of lines and hoses.

I think (I'm not sure) there is a way to electronically test your EVAP system, but you need a sophisticated scanner that plugs in your OBD-II port to see exactly when your canister purges and to measure the vacuum in the lines (Again, I'm not sure if there is a sensor that measures vacuum in the lines, but how else would the code be tripped?). I'm not an expert in the operation of the EVAP system, but I have a general idea of how it works.

Does anyone want to chime in that know specifics on the EVAP system? Again, I'm not as familiar with it to give a specific diagnosis as some others on this forum, but this is my two cents.

Good Luck,

ERUSH

 

[REDDY]

well, finding radiator fluid drips down side of my engine and finding some on transmission that cant be too good, would any of that have to do with the codes, dont see how that make it run lean, starting to think its o2 sensor but dont want to pay $50 and that isnt the problem and start shotgunning it

 

[ERUSH97XLT]

Uh Oh. . .

You have coolant on the side of your block!? That's not good. Where are you seeing coolant EXACTLY? Is it oozing from the cylinder head? Or is it caked around the freeze plugs? If it's coming from the head, that's steering me toward a head gasket issue. Can you perform a compression test?

Just to clarify, your O2 sensors may not just be responsible for lean codes. Many, many things can cause your engine to run lean or cause your engine to think it's running lean. Too much air, too little fuel, or poor ignition can cause a lean condition to exisit in your engine. Too much air usually points to a vacuum leak (in your case, maybe a leak in your EVAP lines), poor MAF operation, or other air related sensor issues (i.e.: IAC, IAT, etc.). Too little fuel means a clogged filter, low fuel pressure, or EVAP issues (yes, your engine accounts for those extra vapors). Poor ignition will cause your O2 sensors to register the unburnt oxygen and tell your engine to use more fuel (indicating a lean condition). This usually implies bad spark plug(s), bad wires, or coil issues.

I'm curious if a bad head gasket would cause a lean condition by drawing in air on the intake stroke. Has anyone had this experience?

A few different things may be happening here. Some may be isolated issues, and some may be related. The P0171 and P0174 are definitely related (they usually trip together). The P0455 may be causing your lean codes by allowing extra, unmetered air to enter your intake; however, it may be a gas cap issue or something else separate from your lean condition. If that's the case, I would check for vacuum leaks, low fuel pressure, and for proper ignition to diagnose your lean codes.

Your coolant issue, I'm guessing, is another, separate, issue that needs to be looked into. I hope it's not your head gasket. The codes you have now will become the least of your worries.

What do others think?

Best of Luck,

ERUSH

 

[ERUSH97XLT]

From my Ford Service Manual. . .

Hello again,

I looked up your P0455 code in my Ford Service manual. This is what it says (word-for-word) to check on your EVAP system:

-- After market parts and accessories nonconforming to the EVAP system specifications.

-- Damaged, missing or improperly installed fuel filler cap.

-- Blockage in fuel vapor hoses/tubes (EVAP canister tube, EVAP canister purge outlet tube or EVAP return tube) in EVAP system.

-- Disconnected or cracked fuel vapor hoses/tubes in EVAP system.

-- EVAP canister purge valve stuck closed.

-- Canister vent (CV) solenoid stuck open.

-- Fuel tank pressure (FTP) sensor malfunction.

-- EVAP canister leaking.

-- Fuel vapor control valve tube assembly blocked.

-- Fuel vapor vent valve assembly blocked.

As it says, cracked EVAP lines can cause the leak. It can also cause a vacuum leak (and therefore a lean condition). If there is no leak in your lines, it could any number of the above things listed (thereby making your EVAP issue independent of you lean codes).

Just an FYI,

ERUSH

 

[Riken]

so the
-- Fuel tank pressure (FTP) sensor malfunction.
is the only pressure sensor in the evap system? i knew they had to be checking pressure, just weren't sure how or where.

i guess obd2 isn't smart enough to increase fuel as air entering is increased. mine is pre-detonating because of an EVAP leak. i guess i can rule out the gas cap.

 

[ERUSH97XLT]

Our vehicles are smart enough to increase fuel with "umetered air". Here's why:

1. The engine assumes all the air entering the engine passes through the MAF sensor and passes by the IAT sensor. These sensors inform the engine EXACTLY how much air (in lbs mass) is entering.

2. The engine then calculates EXACTLY how much fuel (in lbs mass) needs to be injected in order to achieve a perfect air/fuel mixture such that all the oxygen is consumed. I believe the ideal ratio is 14.7:1.

3. After the mixture is burnt, the oxygen sensors confirm the absence of oxygen in the exhaust stream. If they detect more oxygen, it corrects the engine's fuel mixture and commands more fuel to be injected. If they detect no oxygen, the oxygen sensors tell the engine to inject less fuel until oxygen is detected.

There are fuel correction limits. If the oxygen sensors tell the engine to grossly enrich the mixture due to excess oxygen, the engine knows there is a problem with metering the incoming air (hence the lean condition) and will set off trouble codes. On the other hand, if the oxygen sensors tell the engine to excessively lean out the mixture, the engine knows there is a problem with fuel delivery (hence the rich condition).

Does this help? Again, I bet the problem ultimately lies with your EVAP system; a leak somewhere is allowing excess air to enter the engine and causing the oxygen sensors to enrich the air/fuel mixture excessively (hence your EVAP code and lean codes).

There are "professional" ways to locate leaks in your EVAP system, using smoke and other means, but if you can pressurize the system to about 1.0 psi (1.0 psi being the upper limit with a VERY accurate regulator on a small air compressor), you can hear the leak. This has worked for me in the past. There should be a schraeder valve beneath your battery that is labeled as an EVAP test port. I can't emphasize enough to be VERY CAREFUL when doing this; many things are delicate and can easily be broken with too much pressure. It may be worth it to have a trained mechanic use a smoke machine to locate you leak.

Hope this explains a little. Does anyone else have any tips?

ERUSH

 

[REDDY]

ford now raised fuel filler necks to $300-320 because of emergency order, i guess every1's is going at once and ford had to draw up new contracts with more materials to meet the demand, mine wasnt so bad, i replace vapor/vent hose and did the trick, every1 with a explorer start checking, mine rusted from the inside out on vent side, cleaned it off and got new hose all good

and that took care of emissions 455 code

 

[Riken]

my o2's are showing 'out of range' though. so they should be compensating. i still have to fix the problem. the haynes manual says to connect a vacuum to the solenoid and it should hold for about 20 sec to check the diaphram.

 

[Gator99]

Had same exact codes. From what I understand it's highly unlikely that both O2 sensors go out at the same time. So I checked the gas cap, was not fully closed and locked. Reset the computer by removing the negative battery cable, and no codes thrown after several weeks of regular driving.