2002 C4S - UAOS Install and P0455

My previous thread detailed my failed track day and me installing a UAOS system. Since then I have had three core problems P0455 code - large evap leak, this code comes on around 80 miles of driving if I reset the light Weird engine idle - at cold start, when I reverse out of my spot and pop back into neutral to drive out, the car roars to 2000 rpm. After the engine runs down to normal idle in a normal amount of time. I have normal driving and engine operation for 5-10 mins. Then after that, if I am coasting to a stop in neutral, my engine hangs at 1000/1050 rpm from 10->3mph, once I hit 0 mph the engine bogs down rough to the normal 650-700 rpm. This persists for the remainder of my drive, and if I drive harder the car will be hang a little higher - 1100 rpms, and bog down a little more rough into the 650-700 range. I have noticed that if I shut the car down and then start it up 20 mins later or so, the engine hang does not happen as constantly (Neutral coasting goes immediately to 650 rpm, not hanging at ~1000 rpm). A whistling noise coming from the engine that gets worse with the accelerator. Feels like it is localized to the front of the engine and starts at 800 rpm up to 1300 rpm. I have read this is consistent with a failing AOS (perhaps the UAOS diaphragm failed?) Important details General - The back hose from the AOS to the UAOS accumulator has come off several times, so I bought a worm style clamp and that has held the hose in place since, it has not moved voluntarily since General - The nipple on 3D printed plastic part of the UAOS that meets the plenum and regen valve has snapped under normal driving conditions twice, I am now on my third one. I suspected given my code my regen valve was not working. I put a new one in and the problem persists. I thought maybe the valve not working was causing too much pressure at that nipple and part of my problem Diagnosing P0455 - Smoke test through the brake booster - no visible smoke leaks Diagnosing P0455 - My charcoal cannister was confirmed to be working via bench test by my Indy. My Indy last year put in a new fuel tank vent valve, fuel tank level sensor unit, fuel tank bleeder valve and fuel neck reed sensor when we diagnosed that the car was not filling correctly (this ended up being a rat that chewed a wire). I also have a new gas cap on the car My indy is hesitant to take the car in, and would want to put a factory AOS in the car to see if that remedies the problem, but then I am back at square one. I really do not know what else I can do. I have considered that perhaps the diaphragm is not working, as that is where the whistling noise could be coming from. I have also thought that maybe the hose on the back end of the AOS by the block got loose? Maybe the regen valve is not getting the right amount of voltage to open or close correctly from the wiring from the UAOS?

Test the remote diaphragm* or use its number 1 feature: replace it with a new one in short order. *remove it from the car and suck as hard as you can at the opening that connects to the intake. The valve inside should close immediately. Suck as slowly/little as you can and the valve should allow flow. Any other test result means it's bad.

^^^^^^ First things first !!! Lets do as posted above and do the 30 second simple Manometer test so we can rule out the UAOS System from the equation/discussion/troubleshooting .... Then we will move on to next step ..

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I just did this, the test worked. the diaphragm collapsed shortly after the hard suck, and during the softer suck, the air was passing. Ordered a manometer and a donor URO oil cap that will be coming in tomorrow, so this will be the next order of operations. I plan to drive the car 5-10 miles or so, then come back to my garage and conduct the test. When I drill the donor cap, should I apply some sort of thread locker to seal around the place where I will be drilling and inserting the nipple?

Was able to capture the engine wheezing / noise at around 1200 rpm.

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Like I said, first things first... Lets use the 30 second Manometer test to verify the UAOS System is functioning as designed so we can stop blaming/wondering and take it out of this discussion.. Then hopefully we can move on to the next step ... Use the proper size drlll bit and the proper size tap and some thread tape to seal the threads.... This is the proper way to attach a pipe thread nipple into plastic ..

This may be a coincidence but the p0455 code for mine also started after I installed the UAOS last September/October. I should redo the manometer as I had not done that since I installed the UAOS. Butttt how is a problem with the UAOS involved in the P0455? The EVAP system is to me so overtly complicated since I�ve began on this journey. I also noticed the code comes around 80 miles.

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This is also what I�m trying to understand and why I posted here. I am not saying I know for a fact they are correlated as there have been hundreds of successful installs of the UAOS. I posted this in hopes others had the same issue as me and had done x y or z to remedy it. Have you had any of the same symptoms (weird bogging idle, noises etc)? I have been studying the diagrams snd evap systems and see that the 3D printed nozzle that attaches to the plenum also links the purge valve, which is a part of the evap system. So in a way they�re linked?

@Carlo D @ericdl The code P0455 is an EVAP code,.......... I assure you it has NOTHING to with the UAOS System... UNLESS while installing the system, you have mistakenly unplugged the wiring to the change-over valve and plugged it into the purge valve/regen valve, and vise versa.. IF you are not sure if you have made this mistake, there are several simple ways to verify ... But like I said, first things first,....do the 30 second Manometer test to verify UAOS/AOS function to eliminate this from the accusations/blame/wonder/discussion...

Simple air leaks into the engine (for instance running engine without the oil filler cap on) will cause high idle and such issues.

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I am wondering with what I myself had F up during installation of the UAOS to effect the EVAP system. Absolutely there is no doubt your product works flawlessly. I am putting no blame to your product at all. Again......what did i F up? Cause it's possible I F up something lol.

@Carlo D I have spent "countless hours" trying to imagine what people could possibly F up when doing an install. Installing the UAOS System is literally :: two screws holding the AOS, two additional screws to mount the Accumulator, the resr is some quick connectors, clamps, and two plug-n-play wiring connectors... All can be done in the car in situ, without removing the engine or even the intake. But some people insist on removing the intake or even removing the entire engine ... 6 years ago when I Invented the UAOS System I was discussing the Customer Support with a couple of people who had upgraded parts for our cars . I was telling them that I didn't think the Customer Support would be that bad since it was only two screws and plug-n-play connectors more than just a regular AOS replacement, they told me I will be astonished by how much/many things people will F up when doing anything under the hood beyond oil changes.....lol...They were right !! But I assure you, the EVAP System and the UAOS/AOS System have NOTHING IN COMMON other than the vacuum source which is the engine ..

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i haven�t had any Of those other symptoms you mentioned.

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Eric told me today that last year he had a mouse eat the wiring on top of the fuel tank....Had a Indy shop repair the wiring, then replaced the fuel neck seal due to a leak and also a "valve" on top of the fuel tank..... I'm pretty certain the source for his P0455 is stemming from all that, or maybe that was the reason for all that.. His rough running and high idle at times after the UAOS install is most likely due to a vacuum leak in the big rubber boots that happens 50% of the time when a first timer R&R's the intake.. You have been all over your fuel tank as well.. Like I said, the Manometer test is the "definitive" AOS function Test... And is so simple no one can screw it up..

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yup will do the manometer this weekend along with repeating the intake smoke test to see if there is any vacuum issues around the area connected to the regeneration valve. If you remember, maybe, I had accidentally broken the nipple connector that connected to the regeneration valve and repaired that with JB weld. As I understand vacuum is pulled during the EVAP self test procedure.

Just did my manometer test and got 3.10-3.15 inH2O. In my conversation with Skip, he mentioned that a healthy reading is 4-6 and something lower than that would suggest poor crankcase volume. 0 or 1 would indicate a major vacuum leak or open passage, and readings in the 3s may be a minor leak. I felt a tiny amount of vacuum when I went to pull off the original good cap, which to my understanding is a good thing, and makes a cracked oil fill tube less likely. These readings seem to point back at my weird idle condition and whistling type noise I hear from the engine bay. Later today or tomorrow morning I intend to disassemble the plenums and make sure they are on correct, as that is the likely culprit of my bad idle, and the poor manometer reading. I am also beginning to believe that the EVAP code is indeed a separate non correlated issue, but its one problem at a time. I want to solve the rough idle and then get a good manometer reading and then go back to my indy and have them take a look since they did a lot of work on that system less than a year ago. I also got P0430 and P0420, the later of which is new. P0430 has been a on and off code which I attribute to my fabspeed X pipe and have not really cared to solve that

I drove 25 miles after taking apart the plenums and the weird idle is less frequent, the noise persists and I didn�t drive enough for the evap code to register. My manometer read 2.7 vs 3.15 after I did the whole reassembly and first drive. Before I took apart everything I decided to smoke test from the intake Plenum to see where smoke was coming from. I saw that smoke was coming from where the diaphragm�s hose meets the 3-D printed part attached to the Plenum. I then took that Oetiker clamp out and put on a tighter screw on clamps and did not see any more smoke come from there - replacing the oetiker and pressure clamp. I did not see any smoke coming from the Plenum, but proceeded to disassemble the Plenum and reinstall it. I also saw a leak from the nipple to the purge valve, and swapped for a tighter clamp to remedy this. I took particular care to notice where the arrows were as well as on the right hand side of the Plenum, where the Plenum meets the coupler there�s an indentation where they�re supposed to meet. I used a borescope to make sure that the Plenum was as flat as possible along those ridges. I�d reinstalled everything and then proceeded to do another smoke test with the engine at ride height in the air. I had done one previously where I messed up the plenums and saw a huge leak, this was not the case on this second try. There were only two visible places where smoke were coming from. One from the back of the accumulator (It seems like where the aluminum housing is there are some minuscule cracks where air escapes - i don�t know if this is a problem). Then there is another tiny smoke whisper where the 3-D printed collar meets the 3-D printed device that goes into the Plenum. I took pictures to see how that sits as you can twist the collar to see where the fit looks like. The core leak I believe was fixed as my idle behavior has gotten slightly better. I�m not sure how to proceed on these other two leaks and my problem likely persists. I can make the collar leak a little smaller by manipulating where hoses sit a little further from their natural place to make the nozzle sit further into the plenum, but it�s still a leak. And the aluminum accumulator gets smoky and I don�t have a fix for that, nor do I know if that is supposed to do that.

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Porschetech what�s your suggestion?

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Yeah I started to respond to this post earlier but I saw a lot of comments but I didn't see a Technical Question pointed to me so I waited... The "STEP ONE " was passed with flying colors !! .......The Manometer Test of any numerical number less than negative 6 inh20 means the UAOS Flow Regulator/Diaphragm is functioning properly ....... So the UAOS System can be eliminated from this Issue Analysis .. " Step Two " ::::: since Step One has passed, Step Two is to check Fuel Trims to see how much fuel the DME is adding or subtracting from the ideal value...( Test Results will determine next Step ) In this scenario the Smoke Test would have been " Step Three " ..... but a Smoke Test is a good idea and is definitive at any time....Any smoke visible should eliminated ....( No intake system is 100% leak free but very tiny leaks are compensated for by Fuel Trims ) The O-ring at the intake manifold needs to be carefully inspected for damage and if no damage I have successfully used a slightly thicker O-ring to tightly seal that connection..... The OEM O-ring is 23mm x 18mm x 2.5mm but this 23mm x 17mm x 3mm seals tighter Amazon.com: uxcell Nitrile Rubber O-Rings, 23mm OD 17mm ID 3mm Width, Metric Sealing Gasket, Pack of 10 : Industrial & Scientific Amazon.com: uxcell Nitrile Rubber O-Rings, 23mm OD 17mm ID 3mm Width, Metric Sealing Gasket, Pack of 10 : Industrial & Scientific After repairing any leak detected from Smoke Tests, and analyzing Fuel Trims , the next Step can be formated ..

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I ordered these rings and will swap it out once they arrive. What should I be looking for when I analyze fuel trims? I did some research and saw this �Take a look at your STFT and LTFT in live data. If it's really high, say 25+, and you snap the throttle open and it drops to zero, you have a vacuum leak.� I plan to do this next time I drive and have the engine warmed up proper

@ericdl What to look for in Fuel Trims will depend on exactly what year model your 996 is ( DME variation ) and also what Test Equipment you have... Different year models have different terminology for Fuel Trims and also different Testers use different terminology also different protocol for display values... I don't see your year model or test equipment listed in this thread.. I strongly recommend the PIWIS ( you can get a PIWIS set-up in here for $75) or a Durametric , which uses the same Protocol and Terminology as OEM .... I suspect you are using a Generic OBDII tester since you mention STFT and LTFT which are Generic/Domestic Terminology ..... I don't recommend or use the Generic OBDII/Domestic stuff , it just doesn't coincide accurately enough with Porsche products... Tony Callis has a good video explaining the Fuel Trims and PIWIS/Durametric Terminology and values...

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In the process of doing the at home PIWIS set up. I previously had a cheap ancel OBD2 reader I used to read simple codes. Hopefully this PIWIS clone set up comes soon so I can keep working on the car and fix this. I wonder about driving the car in the interim - cylinder wash and all of that. In my mind if the vacuum leak is so small I don't get a code, its probably not dumping as much fuel in the system that I would be washing out the cylinders.

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where are you? Never mind Miami lol

@ericdl If the Fault Code P0455 is the only one you have ( you haven't listed any other ones) , then you have no worries in driving the car...P0455 is Emmisions ONLY and will have no effect on the engine running if there is no other Fault Code accompanying it .. The DME Fuel Trims are designed to compensate for small variations in fuel delivery and variations in MAF readings and/or small vacuum leaks... It monitors the Mixtures via the Oxygen Sensors Feedback and corrects for small variations... The DME knows when things get too far out of range ( set-point values ) and will set a Fault Code if things are too far out of whack ... But looking at Fuel Trims accurately is a good way to see "How much " the DME is doing to correct for small variations to "help" with analysis ....

As I drove the car around 750 miles since this post, I have been clearing codes and for the last 300 miles I now only get P0444 - which is EVAP System Purge Control Valve A Circuit Open. I plan to spend Weds testing the purge valve (which I just replaced)