p0441 woes

[jonan]

so after replacing all of my vacuum lines with silicone/034 lines, i've been getting a persistent p0441 CEL...i've been researching and while there are a few threads on AZ, most of them aren't very specific...

i've never gotten this code prior to changing out my lines (i didn't delete any part of the vacuum/PCV system), here is what i've done so far:

1. confirmed all check vavles are flowing in correct direction
2. confirmed all hose clamps are tightened down
3. replaced n80 valve

the hard lines in the EVAP system are pretty pricey so before i start systematically replacing all of those lines i was hoping someone had any ideas to fix this stubborn bitch of a CEL...

on the ross tech wiki one possible solution is "Check Pipes between Tank Breathing and Throttle Body", what exactly is the wiki referring to? this CEL is eating away at my soul...

if i were to replace the hard lines in the EVAP system it would cost me over $300 on GAP...FML, i was about to piece together my GTRS but am refraining from doing so until i get this CEL resolved...the shitty part is that there are soooo many components to the EVAP system that using the scientific method of replacing shit until the CEL goes away will quickly become cost prohibitive...

so pray tell...other than a faulty n80, what other solutions are there to p0441?

[old guy]

Since you didn't have this problem before replacing all your check valves I have to suspect something is hooked up incorrectly or you have a faulty check valve.

Let's start at the N80. Attached to the N80 is the "Y" shaped hose. The right arm of the "Y" has a check valve. Confirm that you can blow air through the check valve toward the TIP. Confirm that you cannot blow air through the check valve toward the N80. Then trace the line from the check valve to the TIP. Make sure it got hooked up to the TIP connection. Since it's hidden underneath the TIP it's very easy to overlook.

Next disconnect the left arm of the Y and confirm that you can blow air through the line. This line runs behind the block, through a check valve, through a "T" connection and ultimately attaches to a vacuum nipple underneath the throttle body. Then disconnect the hose from the nipple under the throttle body and confirm that you cannot blow air through the line from the nipple end of the hose.

Now go back to the "T" connection underneath the intake manifold. There is a check valve at the base of the T. You should be able to blow air through the check valve toward the T. You should not be able to blow air through the check valve toward the line going under the fender and ultimately to the LDP.

And last but not least make sure you didn't mix up the two quick disconnects that attach the LDP and vacuum canister lines going underneath the front fender.

Edit: One more thing. About one minute after starting your engine you should be able to hear the N80 cycling. It will be a fast ticking noise as it rapidly opens and closes.

[jonan]

thanks old guy!!!

so i did a bit of wrenching per your instructions this morning:

- Confirm that you can blow air through the check valve toward the TIP - CONFIRMED
- Confirm that you cannot blow air through the check valve toward the N80 - CONFIRMED
- Then trace the line from the check valve to the TIP. Make sure it got hooked up to the TIP connection. Since it's hidden underneath the TIP it's very easy to overlook. - CONFIRMED
- Next disconnect the left arm of the Y and confirm that you can blow air through the line - CONFIRMED
- Then disconnect the hose from the nipple under the throttle body and confirm that you cannot blow air through the line from the nipple end of the hose. - CONFIRMED
- You should be able to blow air through the check valve toward the T. You should not be able to blow air through the check valve toward the line going under the fender and ultimately to the LDP. - CONFIRMED
- And last but not least make sure you didn't mix up the two quick disconnects that attach the LDP and vacuum canister lines going underneath the front fender. - CONFIRMED

after confirming everything you asked about, i started the car...idles at 1200 for morning start as usual...set timer on my android for one minute...one minute passes and n80 is NOT clicking...restart timer for one minute...still no clicking on n80...

set timer for two minutes...still no clicking on n80...it's brand new and less than a week old so at this point i'm pretty pissed about it and decide to go for a drive...reset my CEL and off i go...do my usual 15 mile freeway test drive loop, no CEL yet (hopefully it remains that way)...pop the hood and now the n80 is clicking so i'm at a loss...

i'll be running a few more errands today and will report back, i pray to the gods that the CEL stays off, this is the most stubborn code i've had in 12 years of ownership!!! usually when i pull a code, it goes away for good after implementing the most common solution...

[old guy]

I think I mislead you a little on the N80 cycle. With a warm engine the N80 typically starts to cycle in a minute or so.

On a cold start it will probably take four or five minutes before it starts to cycle. First the ECM has to complete the SAI cycle. Then it performs a Evap system leak down test. After that is completed it will start the N80 evap purge cycle. So it takes a little longer.

Fingers crossed that the CEL stays off!

[jonan]

FML, so CEL turned back on while i was running some errands...

car idles at -21 to -22 vacuum and holds boost steady at 18-19 psi on freeway...not sure what the next course of action should be...

perhaps the silicone lines i used in place of the stock ones under the intake manifold are tripping the CEL??

[jonan]

would a leak in the hard plastic line #39 throw a p0441? i'm thinking this may be the cause as it is one of the few original lines that remain and may have developed a small hairline crack that i am not detecting when i was changing out my lines per the a4darkness thread...

[old guy]

Line #39 is part of the vacuum storage/supply needed by the N112 and N249 valves. It has nothing to do with the evap system.

Here's one more thing you can check. If the evap purge line from the canister to the N80 is crushed or kinked the hydrocarbon fumes will not make it to the N80 to be purged through the intake. Disconnect the N80 and use your air nozzle to blow air into the evap line that connects to the N80 and runs back toward the rear of the car. Set your regulator to no more than a few PSI of pressure. While blowing the air into the line have someone go to the drivers side rear wheel and listen for air hissing out of the LDP vent. If you can't get any air to blow through the line you will have to find the source of the restriction.

[jonan]

hmmm, the hardline that is to the left of the n80 seems really loose and flops around pretty easily...i may have damaged it when i was forcefully prying the old rubber lines off of it...

i'll have to pull the fender liner when the weather warms up to see if i damaged anything...

[old guy]

hmmm, the hardline that is to the left of the n80 seems really loose and flops around pretty easily...i may have damaged it when i was forcefully prying the old rubber lines off of it...

i'll have to pull the fender liner when the weather warms up to see if i damaged anything...

Try blowing air through it as I suggested. If you kinked the line you won't be able to blow through it. I doubt the line is broken/cracked. If it was you would get a DTC for a small/large evap leak.

[jonan]

yea, i can blow through it...any other ideas?

[old guy]

yea, i can blow through it...any other ideas?

I'm running out of ideas.....

One possibility is that you have a kink in one of the evap hoses that you replaced and it's sucking flat when the manifold is under vacuum. Consequently the A/F isn't changing when the N80 is cycling.

[jonan]

hmmm, that is entirely possible...i rigged up my three way check valve using a t-splitter and a two way check valve similar to the way lookaught did in the engine strengthening thread...





similar to him i used some silicone line with a 4mm ID to connect the T to the check valve the leads to the manifold and the check valve on the F hose...do you think a kink in one of those hoses under vacuum could be the source of my tribulations??? i may have to go back to the OEM three way check valve as well as the OEM line that connects it to the F hose check valve...

[old guy]

Those hoses that you are referring to above are not connected to the evap system. They are part of the vacuum/storage supply needed for the N249 and N112 operation. They would not be a cause for the P0441.

[jonan]

so i racked my brain all night and when i finally fell asleep i dreamed of this damn EVAP system in virtual EKTA reality...there is no way in my mind that old guy could not help me diagnose what was going on...

well...old guy FTMFW on the fuking money again...despite all of my check valves being brand new from USPlastics...i finally accepted the fact that it was mathematically probable i was a victim of a manufacturing defect, mathematically expressed as:



in other words, for every million check valves that USP produces there is a certain acceptable percentage of check valves that they deem can be defective...i don't know what their (alpha) level of confidence is, but i was certainly victim to it...

Since you didn't have this problem before replacing all your check valves I have to suspect something is hooked up incorrectly or you have a faulty check valve.

unfortunately for me, because all of my check valves were brand new...i didn't take into consideration old guy's sage advice...

rather than just blowing through the hoses with my mouth to test for proper function, i pulled each and every check valve and tested them for proper function in both directions with a can of compressed air...this guy here was definitely out of spec because if i blew against the direction the check valve was supposed to flow...it would take a considerable amount of force in the proper direction until the valve actually opened and began to flow again...



good thing i ordered a few extras because the USP valve i replaced it with did not have this issue...in fact, i could audibly hear the internal diaphragm of the defective check valve clicking as it opened and closed...so far, this is the longest i've gone without a CEL...

first time in my life that a brand new car part has arrived in my hands defective from the get go...after a week of wanting to pull my hair out, i no longer want to burn my car to the ground...

old guy, if you ever come to NYC please PM me and i'll be sure to buy you more than a few rounds of drinks!!! this could have quickly gotten expensive as i replaced parts in the EVAP system, when the problem was simply a defective check valve...when in doubt, occam's razor...

[old guy]

Glad you finally found the problem. After all the testing you did a restricted flow is the only thing that made any sense.

[jonan]

FML, cell came back after driving around all day...........

i went from an empty tank to a full tank and car had no problem starting so i can rule out the charcoal canister...



i may go back to using OEM rubber lines for the three way section that is under the intake manifold...

[old guy]

Well that is certainly distressing….

Let’s get back to the basics. When the ECM is performing an Evap purge it runs a duty cycle on the N80 Evap solenoid. If everything is working correctly the LDP opens to provide purge air that gets drawn through the charcoal canister, through the Evap purge line connecting the canister to the N80, through the N80 and ultimately sucked into the intake manifold nipple located just below and behind the throttle body.

The ECM utilizes the front wideband O2 sensor to monitor the A/F ratio. It expects to see a change in the A/F ratio when running the Evap purge cycle. If it doesn’t see that change you will get the code for an Incorrect Flow.

So let’s do one quick check. First make absolutely sure the check valve above the airbox attached to the “Y” after the N80 is flowing air toward the TIP connection and away from the N80. If you put this in backwards the air will be drawn from the TIP, through the “Y” and onward to the intake manifold, thus bypassing or at least diluting the flow through the N80.

Next, with the engine at idle disconnect the “Y” from the N80 and confirm that you have a strong vacuum pull from the base of the “Y”. This will confirm that the lines, connections and check valves between the N80 and intake manifold are intact and working properly.

If all this checks out the next step will be figure out why the purge fumes aren’t making it to the N80 to be drawn through the intake.

[jonan]

so i checked those hoses while the car was idling...check valve is in the right direction and there is vacuum pull from the base of the "Y"; however, strong is a relative term and the vacuum coming from the "Y" was "strong" enough to gently pull my finger into the base of the "Y"...i tested for vacuum during idle through the n80 valve as well as the uppermost three-way hose under the intake manifold connects to the hard pipe...the level of vacuum from the three-way section of hoses was identical in strength to the strength of the vacuum at the base of the "Y"...

also, when i pulled the "Y" off of the n80 while the car was idling i smelled fuel vapors...does p0441 indicate a leak or is it purely for incorrect flow direction??? thanks again for all your help!!!

[old guy]

The ECM gives a code P0441 when it doesn't register the expected amount of hydrocarbon fumes during a purge cycle. When you pulled the "Y" off of the N80 and smelled fumes that would be an indication that the evap system is working. And you are getting a vacuum signal from the intake manifold so that indicates that everything is plumbed properly.

There is a TSB ( TSB 24-08-78) for the 1.8T concerning this particular code where the ECM is overly sensitive to the evap flow. Unfortunately it requires a reflash of the ECM by the dealer which will wipe out your APR stage 1 program and return it to stock.

I do have one more suggestion. The OEM check valves are relatively inexpensive. I recommend that you replace the three USP check valves associated with the evap flow control with OEM check valves and see if that corrects your problem. Since the TSB addresses the Evap sensitivity and yours worked fine before replacing the check valves it could be that there is a slight difference in flow between the USP and OEM check valves that the ECM doesn't like.

You don't need to replace all of the USP valves. Just the one above the airbox and the ones on the right arm and base of the "T" underneath the intake manifold.

Good luck!

[jonan]

sooo, since i'm switching from APR to motoza or REVO in the near future once i finish putting my GTRS kit together, is it possible for either of those tuners to permanently delete the ECM EVAP readiness check while maintaining the functionality of the EVAP system? i don't want to delete it the system or any of its component parts as i like getting good gas mileage and the benefits of the EVAP system, i just want that damned CEL to go away and prefer the silicone hoses and USP check valves over the OEM setup and hoses...

i'm getting like 33 mpg on the freeway and 22-25 mpg in the city and i have none of the symptoms of the system not working properly...i've read about the TSB and one of your prior posts about removing a screen in the n80 valve (i did remove the screen in the n80 btw) and am coming to the conclusion that the ECM is being overly sensitive to the changes in the geometry of the preshaped rubber hoses vs the silicone lines under the intake manifold and other variables between the OEM vs custom silicone lines and fittings that we aren't accounting for...

[old guy]

I can't answer you question about coding out the Evap readiness but I would be surprised if it wasn't an option. If you want to try just replacing the three check valves that I mentioned you can get all three from here for under $10. Clicky click® I suspect that just may be your cure. I purchased a $50 (Dealer price) check valve from here for $12.50 shipped about 3 years ago and it is holding up just fine. Clicky click®

[jonan]

ahhhhh shit....i just realized that i used the larger size 3/8" USP check valves instead of the 1/4" check valves because the ID on the "T" section of hoses under the intake manifold were 8mm and the 3/8" USP check valves seemed to fit better than the 1/4" USP check valves...

if it wasn't raining, i'd change them out...i'll report back once i do and see if that solves the problem for good...

[jonan]

extremely excited to report that i no longer have a CEL, replaced the larger 3/8" USP check valves with the smaller 1/4" ones and have been CEL free for nearly four days...

props to oldguy to helping me diagnose this!!!