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My father (a professional auto mechanic) took about 6 months to find a random engine shutoff during harder cornering in his Toyota, the culprit was a damaged in

My father (a professional auto mechanic) took about 6 months to find a random engine shutoff during harder cornering in his Toyota, the culprit was a damaged inner insulation layer for a few wires within the wrapped wiring harness for the ECU, engine moving on the engine mounts would sometimes cause a slight harness shift and a short would cause a hard reset of the ECU. Another story I have is my computer geek friend finding an issue with my Subaru Legacy, when no other mechanic could (I tried 3). The issue was that the car was old, first gen OBD, he downloaded some legacy asm ECU reader and made a diagnostic cable from spare parts, the issue was that the car would not start when cold, or be extremely hard to start. The culprit was damaged wire that tells the ECU that the engine is in cranking condition, therefore needs a different fuelling mode, without seeing this mode there was not enough fuel to start when cranking. Eventually this was found by hooking up an oscillograph to see the injector impulse length (duty cycle), as the old gen. diagnostic didn't show any errors, he compared a working car injectors to mine when cranking cold and found this. 10 years later I'm still amazed by his skill and dedication, I'd have scrapped the car otherwise. The car was sold eventually to another person who restored it (rust repair mostly) and his wife still drives it to this day, a 1994 Subaru Legacy.

ryandrake 4y ago
Your friend’s fuel issue seems a lot like the intermittent no-start, low fuel pressure issue I have been debugging (3-series) for over a year now. It has defeated three dealerships and two independent mechanics so far, so I’m taking over the diagnosis now. No clue yet but today’s cars have too damn many computers in them.
- karolist 4y ago
  which engine is that? I had an N54 335 for 5 years too, even E36 era BMWs have vastly superior error logging compared to JDM from that vintage. I hope you find your issue, but if it defeated dealerships it sounds troublesome. Log some live data with INPA if it's an older one, I have no experience with BMWs post EXX series to drop any advice...
  - ryandrake 4y ago
    Yea, N54. INPA helps confirm things, but just the idea that you have to pour over logs to diagnose a system that should be simple and straightforward... sigh. My last car was from the '80s and you could wrench pretty much anything you needed to without having to negotiate with a dozen computers running the show.
    - karolist 4y ago
      I loved my N54 dearly, HPFP is a consumable item there though (30-50k miles), I'd change that as a precaution, especially if your car is tuned.
- Spare_account 4y ago
  Take a look at my other comment https://news.ycombinator.com/item?id=35516985 https://news.ycombinator.com/item?id=35516985
Spare_account 4y ago
This methodical approach to vehicle diagnostics is something you can see on YouTube at South Main Auto Repair https://www.youtube.com/@SouthMainAuto https://www.youtube.com/@SouthMainAuto Eric regularly takes the viewer through the entire process including sometimes measuring electronic components with diagnostic tools that include oscilloscope functions.
- PuffinBlue 4y ago
  Pine Hollow Auto Diagnostics goes even deeper. And focuses much more on the diagnostic. These two channels are good together in that they show different sides of the auto repair industry. Ivan has done some parasitic drain diagnosis in the last few videos, including a new custom made logger that he had sent to him for tracking drain over long duration (like overnight or a couple days). If you like South Main Auto and you havent' seen Pone Hollow Auto Diagnistics, I think you'll like it. https://www.youtube.com/c/PineHollowAutoDiagnostics https://www.youtube.com/c/PineHollowAutoDiagnostics
makerdiety 4y ago
Skill and dedication indeed. The cost of being able to determine the root cause of the car problem probably costs more than the car itself. By a factor of ten.
djmips 4y ago
That's a nightmare and sounds like a really bad software bug... I have one like this even as we speak.

ryandrake 4y ago

Your friend’s fuel issue seems a lot like the intermittent no-start, low fuel pressure issue I have been debugging (3-series) for over a year now. It has defeated three dealerships and two independent mechanics so far, so I’m taking over the diagnosis now. No clue yet but today’s cars have too damn many computers in them.

karolist 4y ago
which engine is that? I had an N54 335 for 5 years too, even E36 era BMWs have vastly superior error logging compared to JDM from that vintage. I hope you find your issue, but if it defeated dealerships it sounds troublesome. Log some live data with INPA if it's an older one, I have no experience with BMWs post EXX series to drop any advice...
- ryandrake 4y ago
  Yea, N54. INPA helps confirm things, but just the idea that you have to pour over logs to diagnose a system that should be simple and straightforward... sigh. My last car was from the '80s and you could wrench pretty much anything you needed to without having to negotiate with a dozen computers running the show.
  - karolist 4y ago
    I loved my N54 dearly, HPFP is a consumable item there though (30-50k miles), I'd change that as a precaution, especially if your car is tuned.
Spare_account 4y ago
Take a look at my other comment https://news.ycombinator.com/item?id=35516985 https://news.ycombinator.com/item?id=35516985

Spare_account 4y ago

This methodical approach to vehicle diagnostics is something you can see on YouTube at South Main Auto Repair https://www.youtube.com/@SouthMainAuto https://www.youtube.com/@SouthMainAuto Eric regularly takes the viewer through the entire process including sometimes measuring electronic components with diagnostic tools that include oscilloscope functions.

PuffinBlue 4y ago
Pine Hollow Auto Diagnostics goes even deeper. And focuses much more on the diagnostic. These two channels are good together in that they show different sides of the auto repair industry. Ivan has done some parasitic drain diagnosis in the last few videos, including a new custom made logger that he had sent to him for tracking drain over long duration (like overnight or a couple days). If you like South Main Auto and you havent' seen Pone Hollow Auto Diagnistics, I think you'll like it. https://www.youtube.com/c/PineHollowAutoDiagnostics https://www.youtube.com/c/PineHollowAutoDiagnostics

makerdiety 4y ago

Skill and dedication indeed. The cost of being able to determine the root cause of the car problem probably costs more than the car itself. By a factor of ten.

djmips 4y ago

That's a nightmare and sounds like a really bad software bug... I have one like this even as we speak.