21 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHParameters after rebuild
Leading reported evidence
Check exhaust leaks
Performed · outcome unconfirmed
No successful repair reported for this finding.
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1
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Read evidence and context
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Performed · outcome unconfirmed · Original poster
Checked for exhaust leaks with a little soapy water (before it warmed up) no issues.
Leading evidence: 'Check exhaust leaks' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'issue' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Check exhaust leaks' (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.
Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.
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Performed · outcome unconfirmed
I was chasing a lean condition after a failed smog test 2 years ago and ended up replacing the o2 sensors and MAF.
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Suspected cause · Original poster
I�m guessing that since I have high numbers on both banks it�s most likely an issue that�s common to both banks, like the vacuum leak, weak fuel pump, secondary air injection.
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issue
No successful repair reported for this finding.
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Identified cause
1
Suspected cause
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Read evidence and context
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Suspected cause · Original poster
I�m guessing that since I have high numbers on both banks it�s most likely an issue that�s common to both banks, like the vacuum leak, weak fuel pump, secondary air injection.
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
21 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
3 acknowledgements have no verified action link; they do not establish a repair result.
Outcome without a verified action link
Moving in the right direction but still not in spec.
Did the first drive this morning, 50 miles. The car felt great, pulls hard, idles perfectly, no CEL. I plugged in the Durametric after I got back and have some borderline readings. I�ll list them below
should I be concerned or do I need to finish the break In period before worrying about them.
Engine Roughness- all cylinders are bouncing around between 0 and .6 except cylinders 2 and 4. 2 is 1.5-2.3 and 4 is -1 to -1.6
Fuel trims- FRA bank 1- 1.13
FRA bank 2- 1.13
RKAT bank 1- 1.59
RKAT bank 2- 1.69
Cam deviation- bank 1- -2.83
Bank 2- 1.63
did I do a **** poor job on the timing? I checked it so many times�.
like I said it seems to be running great�
I hadn�t done a smoke test after getting the engine installed, I did one before installing with the brake booster plugged.
figured I�d do another one just to see. I had the slightest of leaks on the elbow. I�ll replace the elbow with a short piece of hose for now and see if that makes a difference in the fuel trims.
Your cam deviations look fine. Are your fuel trim readings from durametric (values vs. percentages I assume)? If prior, those don't look good. I assume the dash prior to the number is you seperating the number from the text vs. noting positive or negative value? If prior, list if it's a positive or negative value.
If the fuel trim readings are actual values and not percentages, you should be showing fault codes soon. Sounds like you are already going down the path to improve those. I haven't followed your build but LN's recommendation is not more than a 5% deviation on fuel trim for break in.
Using a Durametric, so actual values I believe. The fuel trim numbers are all positive.
I should also note that I replaced the MAF (Bosch), O2 sensors (Bosch), coils, plugs and had the injectors tested/overhauled.
thanks for the list. I�m guessing that since I have high numbers on both banks it�s most likely an issue that�s common to both banks, like the vacuum leak, weak fuel pump, secondary air injection.
I pulled the battery overnight to reset everything to factory specs again. I�ll fix the small vacuum leak and give it another short 10 mile drive to warm up and check it again. Hopefully I�m not going to harm anything by doing so.
Moving in the right direction but still not in spec.
FRA bank 1. 1.14 No change
FRA bank 2. 1.13 no change
RKAT bank 1 .66
RKAT bank 2 .66
i did make a discovery, o2 resistance pre cat bank 1 64 while o2 resistance pre cat bank 2 is 0. I can�t seem to find any info on what they should be but I�m guessing 0 isn�t correct.
would that impact trims on both banks??
I did increase in size. From 3.4 to 3.8� if I�m understanding the statement behind the question increased displacement would require more fuel to keep the mixture where it�s supposed to be. Is that correct??
thanks!
Yes, correct. However, the MAF will measure the greater amount of air being sucked into the bored-out engine and the DME will inject fuel accordingly. From what I've read on here, the DME can compensate and doesn't require re-calibration of fuel and/or timing maps.
Compensation for increased displacement cannot be done via long term fuel adjustment as that is limited to 3% before a CEL is shown and 3.4->3.8 requires 10% more fuel (on average).
As such and in your case any compensation by the DME points towards either too much air or too much fuel and requires identifying and removing the cause.
I removed the o2 sensor that had a resistance of 0 and put the original back in. It did make a significant change.
I did realize that the FRA numbers are a % and not value. Still not sure if what I�m reading is good or not. Also, both FRAs went to 1.02 when under load.
I checked fuel pressure and fuel flow today. Both were good. Checked for exhaust leaks with a little soapy water (before it warmed up) no issues.
the last piece of the puzzle are the injectors. New ones will be here soon. Probably install next week.
Looks like it. I�ll put some more miles on it tomorrow.
I got the o2 sensors from Advanced Auto, new Bosch. I�d assume a big national brand wouldn�t have the fakes so one must have slipped through.
Could be a bad connector, bad wire or just a defect. Hell my harness connecor at the dme was bad on my swap and u chased o2 issues for 6 months. Be glad it was just the sensor.
I was chasing a lean condition after a failed smog test 2 years ago and ended up replacing the o2 sensors and MAF.
As part of my research I came across this info from Callas Rennsport that I saved.
https://www.callasrennsport.com/blog/porsche-986-996-987-997-fuel-trim-information
"The Oxygen sensing AKA Lambda or on the later models they call it �fuel trim mean value� is �STFT� short term fuel trim. The TRA or RKAT and FRA or FRAU-FRAO are the �LTFT� long term fuel trim. For TRA and RKAT you want around them �0�. If it is below �0�, the car is running rich at idle and it is taking away fuel in the Idle range. If it is above �0� the car is running lean and it is adding fuel at the idle range. The FRA or FRAU-FRAO should be around �1�.
If it is below, the car is running rich in the cruise range and it is taking away fuel. If it is above �1�, the car is running lean in cruise range and it is adding fuel. NOW, most of the time, when the car has a faulty MAF,it will affect the TRA-RKAT or idle range.
The TRA-RKAT numbers will be LOW or BELOW 0 and the FRA or FRAU numbers may be normal around 1. ALSO, check the MAF numbers with the car at idle. The MAF numbers on a Boxster should be around 15 kg/h. The MAF numbers on a 996 should be around 17 kg/h. The MAF numbers are usually +/- 2 depending on the EVAP situation."
I don't fully understand the differences on how the .1 and .2 engine management works but these were the numbers after the MAF and o2 sensor replacement.
These are the original pre and post cat o2 sensors.
This is correct ....
In this example the TRA is "adding or subtracting" injection time in milliseconds ( ms) to the injection time..example 2.3ms injection time minus TRA -0.02 = 2.28 ms injection time
In this example the FRA is "multiplying " the injection time by the factor of lambda 1 to the injection time...example ; 2.3ms injection time mutiplied by FRA 1.03 = 2.36 ms injection time
This done due to adding or subtracting will give a "finer trim" to the idle range and multiplying by lambda 1 will give "wider/faster trim" to the load range..
Some testers/displays don't use/show "ms or lambda1 " but rather use "%"
would your opinion be that my trims are in the ok range? Seems like the last reading was 1.14 and .05
Should I be afraid to drive it? I�ve done everything except replace the injectors which I will get to next week.
I don't know what tester you are using but the trims are FINE...
Your display shows % for the FRA 1.14 which is OK
Your display for RKAT doesn't specify " ms or %" , but with an RKAT .05 either way it is very good....
Thanks for your confirmation and insight on this!!
yes, the RKAT is in ms.
im still going to replace/upgrade the injectors to the 996.2 based on your recommendation from another thread.
This is a source reference. Confirm exact model applicability in the original material.
