New battery & Alternator causing Trans. Failsafe Prog

[andrewwynn]

@ bc. I thought the mechanic replaced MAF but now I recall the dish soap on the o-ring situation I just thought that was from checking for vacuum leaks.

From my research which was extensive, the follow up on almost every example of somebody replacing a fuel filter on an x5 was a shortly after fuel pump replacement. (Because any relief of gaining pressure from new filter was temporary since the fundamental problem was actually low pressure from the fuel pump).

On my wife's x5, there was a huge gas leak on the siphon pump multiplying the effect of low pressure and it may have been a Mfg defect on a batch of cars as I've read a handful of examples where the siphon pump failing. It's practically impossible for a siphon jet to fail but an o-ring failing do to a "rollover" problem during assembly? Much higher chance.

The fuel filter on x5 is huge. On the order of 100 or 200x the surface area of an old school fuel filter I've replaced on cars back in the carbureted days. The regulator is combined and that part is far more likely to fail and annoyingly can cause very similar symptoms it has a much higher MTBF than a fuel pump so when "low pressure problems" exisit I would first check fuel pressure. I'm considering adding an analog gauge on the return line to the left line of the gas tank. That would basically be a "hours remaining gauge" on the fuel pump. Right at end of life, the fuel pump loses power but since it makes more pressure than needed the engine doesn't "see" that pressure it gets the regulated pressure. The left lobe gets the "leftovers". The math doesn't work exactly like this but say the pump produces 60psi and the regulator sends 50 to the engine and 10 psi back to the tank. When the pump wears out and makes 55 psi. The engine gets 50psi the tank gets 5psi. There is a minimum requirement for the return line in pressure and volume. When it drops low enough it won't pull gas from left to right lobe of tank. This will happen before hesitation is obvious at the engine so the drive to zero DTE test is a great way to easily confirm your fuel pump is making enough pressure.

I recommend at least once or twice a year run your X5 down to single digits DTE to test your fuel pump.

[bcredliner]

Originally Posted by andrewwynn

@ bc. I thought the mechanic replaced MAF but now I recall the dish soap on the o-ring situation I just thought that was from checking for vacuum leaks.

From my research which was extensive, the follow up on almost every example of somebody replacing a fuel filter on an x5 was a shortly after fuel pump replacement. (Because any relief of gaining pressure from new filter was temporary since the fundamental problem was actually low pressure from the fuel pump).

On my wife's x5, there was a huge gas leak on the siphon pump multiplying the effect of low pressure and it may have been a Mfg defect on a batch of cars as I've read a handful of examples where the siphon pump failing. It's practically impossible for a siphon jet to fail but an o-ring failing do to a "rollover" problem during assembly? Much higher chance.

The fuel filter on x5 is huge. On the order of 100 or 200x the surface area of an old school fuel filter I've replaced on cars back in the carbureted days. The regulator is combined and that part is far more likely to fail and annoyingly can cause very similar symptoms it has a much higher MTBF than a fuel pump so when "low pressure problems" exisit I would first check fuel pressure. I'm considering adding an analog gauge on the return line to the left line of the gas tank. That would basically be a "hours remaining gauge" on the fuel pump. Right at end of life, the fuel pump loses power but since it makes more pressure than needed the engine doesn't "see" that pressure it gets the regulated pressure. The left lobe gets the "leftovers". The math doesn't work exactly like this but say the pump produces 60psi and the regulator sends 50 to the engine and 10 psi back to the tank. When the pump wears out and makes 55 psi. The engine gets 50psi the tank gets 5psi. There is a minimum requirement for the return line in pressure and volume. When it drops low enough it won't pull gas from left to right lobe of tank. This will happen before hesitation is obvious at the engine so the drive to zero DTE test is a great way to easily confirm your fuel pump is making enough pressure.

I recommend at least once or twice a year run your X5 down to single digits DTE to test your fuel pump.

I would not be surprised at all if the problem is fuel delivery. I have never even implied it isn't. And I acknowledge the replacement MAF got rid of the dash warning. But since the mechanic had diagnosed the problem as the MAF and the symptoms did not change and since, as I understand it, OP purchased a used MAF, I think it prudent to confirm the MAF is working properly before moving on to troubleshooting for a fuel delivery problem, close out the possibility of one potential cause before moving to another. If I had said, it sounds like, it appears, it seems to me or I think which are often used in place of assume, I wouldn't have left myself open for criticism. Just as I assumed the mechanic knows what he is doing, it is an assumption that the mechanic did not. When there is more than one problem that can cause the same symptoms we all make assumptions from the input provided to come to our conclusion. Too often there is a race to be right or folks get defensive when there conclusion appears to be challenged or does not become the focus of troubleshooting. I have no problem if the MAF is assumed to be fixed and the focus becomes a fuel delivery issue.

It is not conclusive the fuel pump is bad if your engine quits running at a quarter tank or so. It could be a problem with the fuel level sensor instead of the pump.

[upallnight]

Originally Posted by bcredliner

I would not be surprised at all if the problem is fuel delivery. I have never even implied it isn't. And I acknowledge the replacement MAF got rid of the dash warning. But since the mechanic had diagnosed the problem as the MAF and the symptoms did not change and since, as I understand it, OP purchased a used MAF, I think it prudent to confirm the MAF is working properly before moving on to troubleshooting for a fuel delivery problem, close out the possibility of one potential cause before moving to another. If I had said, it sounds like, it appears, it seems to me or I think which are often used in place of assume, I wouldn't have left myself open for criticism. Just as I assumed the mechanic knows what he is doing, it is an assumption that the mechanic did not. When there is more than one problem that can cause the same symptoms we all make assumptions from the input provided to come to our conclusion. Too often there is a race to be right or folks get defensive when there conclusion appears to be challenged or does not become the focus of troubleshooting. I have no problem if the MAF is assumed to be fixed and the focus becomes a fuel delivery issue.

It is not conclusive the fuel pump is bad if your engine quits running at a quarter tank or so. It could be a problem with the fuel level sensor instead of the pump.

Perhaps the mechanic diagnosis for the trans failure was the replacement of the MAF? I had the gear with the exclamation mark warning come up during my ownership of the X5 and replacing the MAF with a Siemens MAF got rid of the warning. My MAF was also a used one that I bought from a fellow BMW owner with several 3 Series BMW and not from an X5.

[bcredliner]

Originally Posted by upallnight

Perhaps the mechanic diagnosis for the trans failure was the replacement of the MAF? I had the gear with the exclamation mark warning come up during my ownership of the X5 and replacing the MAF with a Siemens MAF got rid of the warning. My MAF was also a used one that I bought from a fellow BMW owner with several 3 Series BMW and not from an X5.

I agree that certainly could be the case, a used MAF could work fine as indicated by the light going out.

We need to hear from Mcfee03. Last post was on the 15th. Unless he passes on more information this might as well be a loud sports bar conversation during a boring football game.

[upallnight]

Originally Posted by bcredliner

I agree that certainly could be the case, a used MAF could work fine as indicated by the light going out.

We need to hear from Mcfee03. Last post was on the 15th. Unless he passes on more information this might as well be a loud sports bar conversation during a boring football game.

Go Packers

Go Cowboys

[upallnight]

here's a great Youtube video on p0171 and p0174 lean code.

https://www.youtube.com/watch?v=nYN-RoFVwAA

[andrewwynn]

After watching the video and combining current and past input I suspect "both" is the answer. Idle lean from MAF and under load lean from low fuel pressure. Need the feedback of what fuel pressure is to know the next step so now we wait.

Great find on that video specifically mentions the heavy fuel trim positive as likely fuel pressure problem. Using torque app to determine that value will be very helpful guidance.

I never knew about the barometric feedback I'll have to see if my app shows me.

[andrewwynn]

Re reading and noticed upallnight mention of MAF fixing trans failsafe. That's amazing to me. Ironic that if engine is low on power the "answer to that" is to make the transmission even harder to push. Just a funny aside.

One more touch on the ass u me concept. I didn't sense any malice and I think it was a succinct way to say: "I think you just interjected something that might not br true will take us all off course on an incorrect path and make all commentary from that point based on that statement foolish. We need to know if that statement is fact or conjecture".

(Using as a given that fuel pressure was determined to make sure only MAF to blame for the codes/transmission).

My repeat of the similar phrase was just a quote from the TV show Friends (Joey messing up the common ass u me and said "you know what they say about assumption. Makes an ass out of you and umption". It's common colloquial English to use the phrase "ass out of you and me" with no insult meant at all. I didn't see it that way eg it was not "not nice" for adult men to use the phrase pointed at each other especially when talking about cars being a pita to diagnose.

I was trying to point out it wasn't out of place for upallnight to use the common phrase to get to the bottom of: do we know or not what test was done before proceeding. Blunt is ok in my book. If my own brother does something dumb I'm going to call him on it by most likely this exact phrase: "hey dumbass". It's the most succinct way to get my point across it's not mean nor demeaning. Of he didn't call me a dumbass when I act like one I would think less of HIM. We are all morons at times. I own up to it plenty (and my last IQ test 15 years out of school was north of 150). It knows how to shut off completely at times "temporary moronity" I call it.

Based on follow up questions it appears that fuel pressure wasn't tested but with a Christmas tree of codes maybe it wasn't possible with defective MAF.

Knock out one thing at a time. It's more than just good news if the transmission isn't failsafe any more and if the only codes are lean both banks that leads to not injectors not coils so less expensive fix. Combining the trans code resolving and upallnight mention of metoo I think that was the next link on the chain. (battery, DISA, alternator, MAF).

OP's MO is to disappear for a week or so before having time to work on the car I suspect waiting for fuel gauge.

I didn't see a reply about what fuel line was disconnected. If the output and return were removed from the regulator and put on swapped it would easily cause the exact symptoms but be fixed instantly by swapping back.

I'm excited that this long haul may be close to resolition and OP can actually use the car!

[bcredliner]

andrewwynn, now you indirectly implying I am dumb, foolish. a dumbass and moron. For someone that is touting a 150+ IQ you must not have been there the day they taught how to win friends and influence people or when to leave well enough alone. Please recall that I said to you it was not necessary the first time and certainly not the second and now the 3rd time is just plain ridiculous. You don't realize that saying-- based on the follow up questions it appears-- means you assume based on the follow up questions the fuel pressure wasn't tested.

FYI-there are no circumstances that I would see as appropriate to call my brother a dumbass. And, Upallnight and I are completely capable of managing our relationship. We don't need a backseat driver.

[andrewwynn]

Bc you read entirely into that wrong 100%. You for some reason I can't fathom take offense at a very common phrase that I've used since I was about 8 and l learned it from Felix Unger on the odd couple. It's my contention that you really have no reason to have thought that was overly un-nice.

I was offended by you taking offense and making my own stand not related to other people. I re-used the phrase on purpose to make a point it it not a derogatory phrase it's merely the expected phrase for the exact circumstance.

What I *implied* was actually nothing at all. What I literally said was that we are ALL guilty of being moronic but only specifically applying that to myself (and my brothers who on occasion as myself deserved the moniker). Example : brother thought it would be funny to touch my neck with a donut just pulled out of hot oil. That is "being a dumbass" and he deserved to be called out on it. Having 7 younger brothers and about to turn 50; there were countless examples when each of my brothers and myself have earned the title.

You I don't know well enough and it would be moronic on MY part to attempt such a misjudgment (to call you dumb or even imply it). I only sense there was some misunderstanding and also that for as I said some reason I can't fathom thought that phrase was meant to be more disparaging than literal.

I did say that maybe you goofed and sent us down a rabbit hole implying that one key test was performed that possibly wasn't and should be verified before going on. Dumb? No not at all. Goof? Oversight ? Sure. I make mine daily nobody's perfect.


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