14 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHFuel Trims Went to Hell
Reported repair
Replace maf and the car is now back
Reported resolution
1
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that report a fix
1
1 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Reported fix · Original poster
I replaced the MAF and the car is now back to normal.
Leading evidence: 'Replace maf and the car is now back' (1 discussions report resolution; 0 report an unsuccessful attempt). Across 1 matching discussions, the most frequently mentioned possible cause is 'either a bad o2 and/or a flakey maf' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Replace maf and the car is now back' (1 discussions). For that action, 1 discussions report a resolution and 0 report an unsuccessful attempt. The most frequently reported fix is 'Replace maf and the car is now back', supported by resolution reports in 1 discussions. 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.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed · Original poster
checked fuel trims again and they are way off now.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed · Original poster
I already replaced the bank 2 upstream O2 that triggered a check engine light.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed · Original poster
That said, tonight I went out in it and it ran great: no hesitation, ran smooth and pulled hard (2k on the new motor).
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.
14 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.
1 acknowledgements have no verified action link; they do not establish a repair result.
Outcome without a verified action link
Still not sure what Durametric calls short term fuel trims unless that is what RKAT refers to.
I have about 2k mi on my new 4.0 (I built). Fuel trims weee pretty good when I first put her on the road. Got a CEL for bank 2 upstream O2. Checked it on Durametric and the sine wave was very irregular. Swapped it out. Driveability is getting worse with it hesitating momentarily off idle.
checked fuel trims again and they are way off now. MAF voltage engine off varies from 1.02v (cold) to 1.03v (hot). Resistance between pin 1-3 is .7kOhm. Bank 2 O2 (the new one) still shows the irregular sine wave (voltage is in range).
I checked for intake leaks but cannot locate any.
I don�t want to throw money at this but suspect either a bad O2 and/or a flakey MAF.
After a few hundred miles on the rebuild (POCs 1-3)
Yesterday with about 2k on rebuild
I would double check for vacuum leaks. Two times now I have found small leak between the lower intake and the head. The leak also goes and comes during the heat cycle.
PS: If you are using smoke to look for vacuum leaks - I would absolutely not stop looking. Good old can of carb cleaner is still my goto for leaks.
@bigboss
Im with you on the vacuum leaks and the carb cleaner method. Still searching.
@yelcab
Im not proficient with Durametric or fuel trims. Is �adaptation� FRA or RKAT?
@yaz996
thanks for the vid. That really helps. Still not sure what Durametric calls short term fuel trims unless that is what RKAT refers to.
I will plug in again and have a looksy.
Why do you say your fuel trims have gone to hell?
Your RKAT values are less than 1% (Max is 6%) indicating no vacuum leaks or rich running..I am also sure you are not having any fault codes showing a fuel trim problem..
@Porschetech3
After further study on the subject (thanks to responses on this thread), I see that they are actually not too bad. The car is just not running very well right now. I think, based on reading on troubleshooting the MAF, it may be going bad. The car is difficult to drive smoothly and hesitates when accelerating. And it just isn�t pulling like it �should�.
That said, tonight I went out in it and it ran great: no hesitation, ran smooth and pulled hard (2k on the new motor).
I was trying to avoid throwing parts at it but all indicators are the MAF is flakey.
One last item I don�t understand is why the RKAT values are so different between B1 and B2.
This thing has not been running right; very rough and hesitating at lower rpm and even worse when cold. Idle would occasionally drop and get rough. I already replaced the bank 2 upstream O2 that triggered a check engine light. That didn�t really make a difference.
I replaced the MAF and the car is now back to normal. Nice and smooth, even when cold, idle is consistent and it now seems to pull like it should.
I measured the resistance between pins 1-3 and got 1.4k ohms on the old one and 2k ohms on the new one for those trying to troubleshoot a problem.
Got the MAF online at Autozone for $131 and free shipping (cyber deal).
I have bad luck with non-factory MAF. To the point where I will only buy from factory, including Porsche. I am glad to know FCP works out for you Jandakson.
To be clear, I bought the MAF from Autozone (chain of retail auto parts stores). The box came with a tamper sticker on it. It has
a serial number that you type into the Bosch website to ensure it is genuine and not a fake. I have seen this more often lately as knockoffs are a real problem that the consumer suffers from.
This is a source reference. Confirm exact model applicability in the original material.
