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THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHFuel trim advice wanted
Leading reported evidence
Check fuel trims and i am super happy
Performed · outcome unconfirmed
No successful repair reported for this finding.
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0
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1
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Performed · outcome unconfirmed · Original poster
I’m not sure why I couldn’t recreate that leak, but after some mixed driving over the last few days I just checked my fuel trims and I am super happy with the results.
Leading evidence: 'Check fuel trims and i am super happy' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check fuel trims again and maybe' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed · Original poster
After the already repaired leaks have been fixed bank 1 RKAT is .98 and bank 2 is 2.3.
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Performed · outcome unconfirmed · Original poster
Replaced the elbow on the brake booster and used a hose clamp instead of the spring clamp on UAOS.
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Performed · outcome unconfirmed · Original poster
I ran another smoke test tonight and was not able to replicate the leak, I did confirm that it was indeed the resonance flap control that I was seeing by going from the topside with my camera, but no smoke leakage this time, confirmed had plenty of smoke in the system.
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Performed · outcome unconfirmed · Original poster
Replaced the elbow on the brake booster and used a hose clamp instead of the spring clamp on UAOS.
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1
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Performed · outcome unconfirmed · Original poster
I’m not sure why I couldn’t recreate that leak, but after some mixed driving over the last few days I just checked my fuel trims and I am super happy with the results.
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0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion · Original poster
I�ve read and searched and some threads say to start by doing smoke test to look for vacuum leaks others recommend cleaning MAF or changing O2 sensors.
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Suggestion · Original poster
Looking to see if anyone has used the billet cap from LN engineering that goes over it and supposedly seals it or is it best to just replace the entire tube?
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Suggestion
No engine will have both sides exactly the same, but if they are way different I would look at cleaning or replacing the injectors first ( or flow testing them ) and the O2 Sensor next ...
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Suggestion · Original poster
I�ve read and searched and some threads say to start by doing smoke test to look for vacuum leaks others recommend cleaning MAF or changing O2 sensors.
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Performed · outcome unconfirmed · Original poster
I ran another smoke test tonight and was not able to replicate the leak, I did confirm that it was indeed the resonance flap control that I was seeing by going from the topside with my camera, but no smoke leakage this time, confirmed had plenty of smoke in the system.
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25 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
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I recently purchased a Durametric and was looking to get some initial baseline data for ongoing comparison. It seems my fuel trims are not great and I�m hoping to get some direction as to where I should start to figure it out. I�ve read and searched and some threads say to start by doing smoke test to look for vacuum leaks others recommend cleaning MAF or changing O2 sensors. I�m new to this and want to be methodical and try one thing at a time and would obviously prefer to not just throw parts at it. I�ll attach my Durametric values and hopefully I can get some direction where to start. This is for a �02 C2, very recent UAOS install with new oil fill tube and track drain included, which I�ve read are likely spots for vacuum leaks, so thinking I can rule those out, but maybe not. If I can provide any additional information that would be helpful, let me know.
[Image-only post; no author-written text. Original image references:]
https://cimg8.ibsrv.net/gimg/rennlist.com-vbulletin/2000x1504/img_2872_eefa78d46646bc7e91a19c2ecbde99ec03d7d5ea.jpeg
Tony Callas has very good info also on this subject with M96 engines.
Theck these two out:
https://www.callasrennsport.com/blog...im-information
You Tube
Thanks, I just watched those, great information. I just put together a manometer vacuum tester and got readings of around -3 inH2O which is a little on the low side, but I believe that skip said UAOS will be lower than OEM. I guess I’ll start with a smoke test looking for vacuum leak.
Ok, I have located and fixed 3 vacuum leaks, I’m hoping I’m down to my last one. Fuel trims have gotten progressively better and hoping this is the last leak, fingers crossed. This leak is what I believe is on the resonance tube. Looking to see if anyone has used the billet cap from LN engineering that goes over it and supposedly seals it or is it best to just replace the entire tube? Searched and couldn’t find any reference/ or threads to the part being used.
Yeah the first fix came from a 996 Rennlister that went to Lowes and got a 3/4 " rubber chair leg cap and sealed the pivot ... The LN Engineering product is a very nice piece
I would not even think about buying the whole rear plenum when solid fixes are much faster, easier, and cost less .....
Thanks for the input, glad to here that is a good fix, seems easier and cheaper than replacing The whole tube. Out of curiosity, would that leak affect fuel trims on one bank more than the other? My bank 2 is more off than 1, was hoping that one of these fixes would get them closer to each other but so far they have been improving fairly equally it seems.
On port injected engines a vacuum leak is unmetered air that is not measured by the MAF sensor but is going into the engine and requires more fuel to achive Stoichiometric balance and is the reason it effects all cylinders mostly evenly ..
The DME on the Porsche is basically 2 three cylinder engines with 1 common MAF Sensor.. ... The O2 Sensors are the feedback per side....so an O2 Sensor that is a little differently sensitive to the other side can cause a slight difference, Also the injectors can be dirtier on one side than the other ...
No engine will have both sides exactly the same, but if they are way different I would look at cleaning or replacing the injectors first ( or flow testing them ) and the O2 Sensor next ...
After the already repaired leaks have been fixed bank 1 RKAT is .98 and bank 2 is 2.3. Injectors are new within the last 4K miles, so hopefully those aren’t the cause. I’ll check out O2 sensors next I guess.
Curious, what were the first two leaks you found? And at what points did you introduce smoke? About to smoke test my own thats showing RKATs at 2.6% and 3.6% so would be interested to hear more.
I introduced the smoke through the intake/throttle body. First leak was at brake booster quick connect elbow, second was on the UAOS hose going in to the accumulator. Replaced the elbow on the brake booster and used a hose clamp instead of the spring clamp on UAOS.
Ok, I’m slowly picking off the leaks, resonance tube plug from LN installed, which then revealed another one, will it ever end? I’m assuming the biggest leaks reveal themselves first and the smaller ones don’t show up until those are fixed, path of least resistance type thing. Can anyone identify this offender, it seemed like it was deep in the bowels somewhere. I snapped a couple of quick shots of it but haven’t had a chance to go back and look again after the smoke cleared. As always, I truly appreciate any help offered.
Looks to me like its leaking from the resonance flap hinge where it connects to the actuator - essentially the same leak as the one you capped but on the other side. Just my guess on the pic though - welcome other thoughts.
^^^Agreed. I think this is the first post showing a leak in this location. And it make sense. If one side wears out, the other should be close. Add another wear out item to the list. Also not sure how to fix it other than replace. I don't think I've seen anyone post a repair for it. (snip lifted from Pelican) Keep going. You'll find them all...
Thanks for the info, totally makes sense and gives me a better idea of where to look, my camera was coming from the bottom, I think I�ll try to come in from the top to see if I can confirm your suspicions. Thanks again, appreciate the help and encouragement!
I ran another smoke test tonight and was not able to replicate the leak, I did confirm that it was indeed the resonance flap control that I was seeing by going from the topside with my camera, but no smoke leakage this time, confirmed had plenty of smoke in the system. Plan to drive as is for a few days, check fuel trims again and maybe smoke test again over the weekend.
I’m not sure why I couldn’t recreate that leak, but after some mixed driving over the last few days I just checked my fuel trims and I am super happy with the results. Drastically improved from my ~2.5 and ~4.5 starting point. I think at this point I’m just going to keep an eye on it and check them again in a week or so.
Our 996 just got a P0174 code so I am relearning Porsche terminology and Durametric scanner operation. Below is the best explanation I have seen of RKAT and FRA:
Originally Posted by
The Radium King
rkat is idle trims
fra is low load trims
frao and frau will always read the same as fra unless in a turbo with wideband o2 sensors
the car does not trim at wot/open loop (no feedback from oem narrow-band o2 sensors to establish trims as ecu richens mixture when engine working hard)
for rkat, values are given as +/- % fuel added, and
you will get cell at +/-4%
for fra, values are given as +/- fuel added from a baseline of 1, and
you will get cell outside of 0.7 to 1.32
This is a source reference. Confirm exact model applicability in the original material.
