Diagnosticare masina cu Chat GPT - studiu de caz

[goangaus]

O sa fie o postare lunga, asa ca va multumesc pentru rabdare 

Dupa cum unii dintre voi stiti, am incercat o buna perioada de timp sa rezolv la al meu G01 (2020 30i 55000 km) un jerkiness la viteze mici de oras, fie la reducerea vitezei pe franare, fie la revenirea pe acceleratie, fie la schimbarea treptelor de viteza. Masina a fost verificata in mai multe reprezentante si mai multe service-uri specializate pe cutii de viteze, s-a inlocuit cutia de transfer pe garantie, s-a verificat nivelul de ulei in transmisie, s-a facut update de soft, simptomele s-au redus dar nu au disparut complet. Concluzia tuturor a fost ca masina nu are nici un fel de problema. 

De ceva timp nu m-am mai agitat cu problema asta, m-am si obisnuit cu acest comportament. Recent o cunostinta tot cu G01 tot cu mici smucituri in mers, dar usor diferite de ale mele, mi-a comunicat ca a rezolvat toate problemele prin inlocuirea actuatoarelor Vanos iar acum masina se conduce complet diferit, fara nici un fel de jerkiness. Facuse inainte test de actuatoare Vanos cu Ista si a iesit OK, am facut si eu si a iesit la fel.

Impulsionat de aceasta "descoperire" si de faptul ca mai am si alte simptome care ar indica in aceasta directie, cum ar fi consum mare (14-15 vara si 17-18 iarna in Bucuresti, colegul cu acelasi motor tot in Bucuresti are consum 12), lag la acceleratie si apoi pleaca tare, nu este liniara acceleratia, vibratii mai puternice la relanti care se simt in scaun si care dispar in mers(suporti motor verificati, confirmat din mai multe locuri ca sunt ok) -> am luat decizia sa fac un data log cu Bimmerlink pentru valorile actuatoarelor Vanos. 

Am identificat urmatorii parametri pentru Vanos inlet, pentru exhaust nu am gasit:

Target angle (inlet VANOS) ° KW - pentru Vanos required

Angle inlet valve opens based on LWOT ° KW - pentru Vanos actual

Fisierul se poate vedea aici. 

Inteleg ca valoarea din actual trebuie sa fie cat mai aproape de required dar ca este normala o anumita diferenta, doar ca nu stiam cat este abaterea considerata normala, asa ca am apelat la ChatGPT, care a venit cu foarte multe detalii utile.

Problema cu AI-ul este ca la un moment dat halucineaza si este greu sa identificam unde are dreptate si unde le infloreste. Am mai gasit pe net cazuri unde laudau ChatGPT pentru rezolvarea unor probleme auto complexe, asa ca sunt cumva optimist.

Rugamintea este pentru cei care se pricep, sa aruncati o privire pe conversatia de mai jos si sa va spuneti parerea daca spune bine ce spune, concluzia este ca abaterile nu sunt mari dar sunt in afara limitelor admise si imi recomanda sa fac o curatare a actuatoarelor, eu inclin mai mult spre inlocuire. 

Quote

On a bmw x3 g01 30i what is the role of vanos actuators?

ChatGPT said:

On the BMW X3 G01 xDrive30i with the B48 engine, the VANOS actuators (Variable Nockenwellen Steuerung, or Variable Camshaft Timing system) play a crucial role in optimizing engine performance, efficiency, and emissions.

Purpose of VANOS Actuators:

The VANOS actuators adjust the timing of the intake and exhaust camshafts by altering their position relative to the crankshaft based on engine speed, load, and other conditions. The B48 engine uses dual VANOS (on both intake and exhaust sides).

Key Functions:

1. Improved Power and Torque: By advancing or retarding cam timing, the engine can produce more torque at low RPM and more power at high RPM.

2. Better Fuel Efficiency: Optimizing valve timing allows for more efficient combustion, reducing fuel consumption.

3. Lower Emissions: Precise control of valve overlap helps minimize NOx and HC emissions.

4. Smoother Idle and Cold Starts: VANOS helps the engine run more smoothly at idle and during warm-up.

How it Works:

• The system uses hydraulic pressure (from engine oil) to move the camshaft via a VANOS actuator/solenoid.

• The engine control unit (DME) commands these actuators to adjust timing in real time.

• The actuators are electronically controlled solenoids that regulate oil flow to the camshaft gears.

Common Issues:

• Oil contamination or sludge can clog VANOS solenoids.

• Electrical failures can lead to fault codes (e.g., P0012, P0015).

• Symptoms of failure: rough idle, poor fuel economy, loss of power, or a check engine light.

Let me know if you'd like diagrams, fault code details, or testing procedures for VANOS on your B48 engine.

Given your symptoms—poor fuel economy, acceleration lag from a standstill, and uneven acceleration at low RPM with no fault codes—it's possible the VANOS actuators are not operating properly, even if they haven't triggered a fault. Here's how you can check the VANOS actuators on your B48 engine:

---

Step-by-Step Diagnostic Approach:

1. Live Data Monitoring (Best Method)

Use a BMW-capable diagnostic tool like ISTA+, BimmerLink, BimmerTool, or Carly:

• Look at actual vs. target VANOS angles for both intake and exhaust.

• While idling and while revving gently, observe if the actual angles follow the target values smoothly and promptly.

• Symptoms of a weak or sticking actuator: slow response, erratic movement, or no change despite target angle requests.

2. VANOS Solenoid Test (Using ISTA+)

If using ISTA+, go to:

• Vehicle Test > Function Test > VANOS Solenoid Actuator Test

• It will cycle the solenoids and report if their movement is within expected parameters.

3. Manual Inspection

If you don’t have access to ISTA or diagnostics:

• Locate the VANOS solenoids (on the front of the cylinder head—intake and exhaust sides).

• Unplug and remove them (they're held by small bolts).

• Check for debris or sludge in the screen filter at the tip.

• You can clean them with electrical or brake cleaner, then reinstall.

4. 12V Bench Test (Optional)

To check movement:

• Apply 12V briefly to the solenoid (off the car) to ensure it "clicks" (activates).

• Caution: Do not apply voltage for too long—just a quick test.

5. Check Oil Quality

Since VANOS is oil-pressure dependent:

• Dirty or old oil can impair actuator performance.

• Make sure you’re using BMW LL-01 spec 0W-20 or 5W-30 oil, and it’s not past its service life.

• Consider changing the oil and filter if it’s due or questionable.

---

If You Suspect a Fault but No Codes:

• Try logging acceleration with live VANOS angle data. Compare response times.

• Alternatively, perform a VANOS adaptation reset (in ISTA or BimmerTool Pro) to re-learn camshaft positions.

---

Would you like a diagram showing the solenoid locations or guidance on using a specific diagnostic app like BimmerLink or Carly?

1/2

4o

 

You said:

About actual vs required angle, how much variance is considered normal?

ChatGPT said:

Great question. On your B48 engine (BMW X3 G01 30i), during live data monitoring of VANOS actual vs. required (target) camshaft angles, here's what's considered normal variance:

---

Normal Tolerance:

• Idle and steady-state:
  ±1° to ±2° difference between actual and required angles is normal.

• During rapid changes (e.g., acceleration or deceleration):
  A momentary spike up to ±5° may occur, but the actual value should quickly follow the target within 1–2 seconds.

---

What’s Not Normal:

• Persistent deviation >2–3° at idle or light load.

• Slow or delayed tracking of the actual angle vs. required under dynamic conditions.

• Oscillations or instability in the actual angle while the required angle is steady.

• One camshaft consistently lags more than the other (e.g., intake always slow, exhaust ok).

---

Important Notes:

• If you see zero movement in actual angle while the target angle changes, it may indicate a stuck VANOS actuator or oil flow issue.

• For best analysis, log data over time and graph both values.

---

Let me know if you want help interpreting logs or data you capture from a scan tool—I'd be happy to review it.

4o

You said:

I have data in csv format, can you check?

ChatGPT said:

Yes, absolutely—please upload the CSV file here, and I’ll review the VANOS actual vs. required angle data for you. I’ll look for any irregularities, lag, or deviations that might suggest actuator issues.

4o

You said:

Vanos intake target is on column h and actual on column I

ChatGPT said:

 

I've found the relevant columns:

• Target intake VANOS angle: 'Target angle (inlet VANOS) ° KW'

• Actual intake VANOS angle: 'Angle inlet valve opens based on LWOT ° KW'

• Time base: 'Time'

I'll now analyze the difference between target and actual angles over time to identify any inconsistencies or abnormal behavior.

Here's the plot comparing the target vs. actual intake VANOS angle over time:

Key Observations:

• The actual angle closely tracks the target angle overall, which is a good sign.

• There are small consistent offsets, but most of the time the difference appears to stay within the ±2° range, which is considered normal.

To be thorough, I’ll now analyze and quantify how often the actual deviates significantly from the target.

 

VANOS Intake Angle Analysis Summary:

• Maximum Deviation: 60.91° (likely an initial transient or data logging artifact)

• Average Deviation: 1.75° (within acceptable range)

• Points > 2° Deviation: 6,268 data points (≈ 20.6% of total)

• Points > 5° Deviation: 1,536 data points (≈ 5.0% of total)

• Total Data Points: 30,483

---

Interpretation:

• While most values are acceptable, about 1 in 5 readings exceed the typical 2° tolerance, and 5% exceed 5°, which is borderline abnormal.

• This could suggest mild actuator delay, oil flow issue, or early-stage VANOS solenoid wear, especially if symptoms like lag or hesitation are present.

• The 60.91° max deviation likely reflects a point where the engine just started, or the VANOS was transitioning.

---

Recommendation:

If you're experiencing drivability symptoms, it's worth:

1. Cleaning or replacing the VANOS solenoids.

2. Ensuring fresh, high-quality oil (BMW LL-01 spec).

3. Performing a VANOS adaptation reset using ISTA or BimmerTool.

Would you like me to isolate and plot the segments with >5° deviation for visual inspection?

4o

You said:

Yes

ChatGPT said:

It seems like I can’t do more advanced data analysis right now. Please try again later.

However, based on our previous analysis, the moments with deviations over 5°—while relatively rare (about 5% of total)—are worth investigating further. If you'd like, I can guide you through how to graph those segments using Excel or another tool locally, or you can re-upload the file later for a deeper dive. Let me know how you'd like to proceed.

4o

You said:

Can vanos actuator cause rough gearbox shifts also?

ChatGPT said:

Yes, a malfunctioning VANOS actuator can indirectly cause rough or jerky gearbox shifts, especially in modern BMWs like your G01 X3 30i with the B48 engine. Here's how:

---

Why VANOS Issues Can Affect Shifting:

1. Engine Torque Irregularities:

   • VANOS controls valve timing, which affects torque delivery.

   • If VANOS response is delayed or erratic, engine torque may not match what the transmission expects, causing hard or rough shifts.

2. Poor Low-RPM Driveability:

   • Hesitation or uneven acceleration caused by bad VANOS operation can confuse transmission logic, which adapts to throttle and torque patterns.

3. ECU & TCU Interdependence:

   • The DME (engine ECU) and EGS (transmission control unit) constantly communicate.

   • If the DME delivers inconsistent torque or throttle data, the TCU may mistime clutch or gear engagements.

4. Misinterpreted Load Conditions:

   • VANOS timing influences engine load calculation. Incorrect cam timing can skew these calculations, making the transmission think the car is under different load than it really is.

---

When VANOS-Related Shifting Issues Are Likely:

• During light throttle or creeping, especially 1st to 2nd gear.

• When there's hesitation before shifting.

• In stop-and-go traffic, where timing inconsistencies are most noticeable.

---

Rule-Out Checklist:

• VANOS solenoid performance (test or clean/replace).

• Engine mounts (worn mounts can also cause shift shock).

• Transmission adaptations (consider reset after fixing VANOS).

• Transmission fluid level/condition.

---

Let me know if you'd like to go through steps for VANOS cleaning, testing, or a safe way to reset transmission adaptations after addressing the root issue.

4o

You said:

I have one more symptom, if I reduce speed and roll the car and then lightly accelerate sometime I have a jerk, like the gearbox is in a gear too low, might this be related also to vanos?

ChatGPT said:

Yes, that rolling jerk during light acceleration—where it feels like the gearbox is in too low a gear—can be indirectly related to a VANOS issue, especially on your B48-powered BMW X3.

Here’s why:

---

1. VANOS Affects Torque Prediction

When you roll and lightly accelerate, the transmission relies on predictable engine torque to choose the correct gear. If the VANOS system isn’t responding correctly:

• The engine torque may be delayed or erratic, especially at low RPM.

• The gearbox may pre-select a lower gear expecting more torque, then overreacts when torque delivery lags or surges—causing a jerk or bump.

---

2. Valve Timing Affects Load Detection

The camshaft timing influences how the engine breathes, and thus how load is calculated. If VANOS is off:

• The engine thinks it's under more/less load than it is.

• The transmission responds based on this wrong data and may choose inappropriate gears.

---

3. Software Adaptation Issues

Over time, the DME and TCU adapt to how VANOS performs. If VANOS is slow, sticky, or drifting, those adaptations may:

• Mask the issue initially but cause drivability problems like rolling jerks.

• Become inconsistent after a restart or oil temperature change.

---

Other Possible Contributors (To Rule Out):

• Transmission adaptation drift (especially if oil is old or shifts are learning around torque errors).

• Throttle lag (can exaggerate the jerk).

• Torque converter clutch behavior in low gears.

• Engine mounts (amplify the perceived jolt).

---

If VANOS Is Suspect, Try This:

• Clean or replace the VANOS solenoids (start with intake side).

• Change oil if it’s old—dirty oil directly affects VANOS performance.

• Perform a VANOS adaptation reset.

• Then do a transmission adaptation reset (in ISTA+ or BimmerLink Pro).

 

[alex230ro]

 videoclipul asta l-ai văzut?

[goangaus]

5 minutes ago, alex230ro said:

 videoclipul asta l-ai văzut?

Da, nu am simptomele de acolo, la urcare panta usoara nu am întrerupere nici fluctuație de cuplu pe sport display cum arata el acolo, face si la mine dar mai putin, cred eu ca e normal, ca nu pot tine acceleratia perfect constanta.

Edited May 15 by goangaus

[alex230ro]

Pai pune pe cruise și vezi.Daca nu ai ce face cu 1000 lei poți lua actuatoarele. Se schimba relativ ușor.

[goangaus]

9 hours ago, alex230ro said:

Pai pune pe cruise și vezi.Daca nu ai ce face cu 1000 lei poți lua actuatoarele. Se schimba relativ ușor.

Am mers si cu cruise si fluctuează putin cuplul, dar mi se pare o metoda prea ochiometrica. Ce-i drept am mers prin oraș cu Cruise pe 50 km/h pe drum drept, mai erau denivelări, am pus fluctuatiile mai mult pe seama drumului. O sa fac un test si in afara orașului pe un drum mai bun sa vad cum e, dar la mine se simt problemele la viteza mica, nu mare.

[alex230ro]

Cum am zis actuatoarele 1000 lei piesele . Cheie daca esti din Bucuresti cred ca am eu pe undeva . LA B58 mai mine facea la fel foarte putin si rar , luasem actuatoarele, le-am dat cu masina .Poti sa mai astepti sa vezi daca se agraveaza si apar si coduri sa nu dai banii degeaba .

Edited May 16 by alex230ro

[goangaus]

Dar de ce spune ChatGPT ce părere aveți, putem lua de bun tot ce scrie acolo? Strict pe cazul prezentat mai sus si detaliile prezentate, analiza datalog, etc.

Edited May 16 by goangaus

[alex230ro]

Chat GPT a facut ce as face si eu a cautat pe net si apoi a facut o compliatie, daca as pune aiurea de 10000000 de ori ca actuatoarele sunt pentru a trage apa la WC as zice ca Chat GPT va lua treaba asta de buna .Pe scurt la momentul asta nu dau 2 bani pe ce zice Chat GPT .Diagnosticul se face cu diagnoza conectata la masina si vazand "fizic" ce e acolo .Erorile si live data ajuta pana la un anumit punct dar nu sunt infailibile si as putea sa iti spun cazuri in care testerul dadea o eroare si problema era ceva simplu . La fel si cu zgomote de suspensie unde ziceai ca bate suspensia dar de fapt era un etrier desfacut si exemplele pot continua .

Edited May 16 by alex230ro

[FiveThreeFive]

@goangaus Iti recomand sa fii foarte prudent cu sfaturile obtinute de pe ChatGPT. Eu am facut ceva experimente cu el, in principal in ceea ce priveste mecanica, electronica, programarea si legislatia - atentie, toate la nivel de curiozitate amatoriceasca.

In programare nu a dat niciun rateu, dar l-am testat putin si la aplicatii foarte simple. In subiecte de legislatie, da raspunsuri foarte bune, dar a tras si cateva greseli impardonabile (spre exemplu, a indicat anumite articole dintr-o lege, fara absolut nicio legatura cu subiectul). In electronica, a gresit complet tema pe care i-am dat-o (a fost una singura, dar de complexitate mare). In mecanica, aproximativ jumatate dintre raspunsuri au fost bune, dar jumatate proaste.

Ca urmare, in spiritul enuntat de @alex230ro mai sus, daca vrei sa consulti ChatGPT pentru a remedia anumite probleme la masina, nu pune in niciun caz baza pe raspunsurile pe care le primesti, ci ia-le doar ca sugestii cu probabilitate mare de a fi gresite.

 

[goangaus]

13 minutes ago, FiveThreeFive said:

@goangaus Iti recomand sa fii foarte prudent cu sfaturile obtinute de pe ChatGPT. Eu am facut ceva experimente cu el, in principal in ceea ce priveste mecanica, electronica, programarea si legislatia - atentie, toate la nivel de curiozitate amatoriceasca.

In programare nu a dat niciun rateu, dar l-am testat putin si la aplicatii foarte simple. In subiecte de legislatie, da raspunsuri foarte bune, dar a tras si cateva greseli impardonabile (spre exemplu, a indicat anumite articole dintr-o lege, fara absolut nicio legatura cu subiectul). In electronica, a gresit complet tema pe care i-am dat-o (a fost una singura, dar de complexitate mare). In mecanica, aproximativ jumatate dintre raspunsuri au fost bune, dar jumatate proaste.

Ca urmare, in spiritul enuntat de @alex230ro mai sus, daca vrei sa consulti ChatGPT pentru a remedia anumite probleme la masina, nu pune in niciun caz baza pe raspunsurile pe care le primesti, ci ia-le doar ca sugestii cu probabilitate mare de a fi gresite.

 

Exact asta fac, stiu ca nu te poți baza 100% pe ce spune ChatGPT dar măcar iti da niste sugestii si eram curios cum pot verifica dacă ce a spus este corect. Din pacate in service-uri nu am gasit oameni disponibili sa faca datalog si sa analizeze datele, toți fac diagnoza si spun ca dacă masina nu are erori atunci e totul ok. Ceea ce este evident ca nu este, demonstrat si de amicul care tocmai si-a rezolvat problema, primind aceleasi răspunsuri in service, masina nu are erori deci nu are nimic.

Am fost la Bavaria, Bforce si Frk fara sa găsesc pe cineva dispus sa faca datalog si sa analizeze live data, daca aveți sugestii de service-uri care au oameni buni pe domeniul asta va rog sa-mi spuneți. Am auzit de bine de Service T-e-a-m, o sa încerc si acolo.

LE: se pare ca nu pot sa scriu numele service-ului de mai sus fara sa fie redenumit automat in Service Scream (Tezparii). E ceva ce ar trebui sa stiu despre ei?

Edited May 16 by goangaus

[alex230ro]

Poti sa faci loguri dupa loguri variatia e mica si nime nu nu va vrea sa riste sa schimbe piesa si problema sa nu dispara .In cazuri ca al tau nu exista - da e actuatorul schimbam si va fi ok .Repet am expieriente in care ziceai ca e un lucru doar ca sa descoperi  - ca de fapt e altceva . Deci bucura-te de masina si cand va fi mai grav iti va spune ea .Mi-am amintit acum cand studiat B58-ul am gasit un site unde baietii aratau ca BMW schimbase "metoda" de a numara missfire urile astfel incat check engine sa se aprinda la un numar mai mare de missfire . Probabil si la Vanos au lasat tolerante mai mari .

Edited May 16 by alex230ro

[goangaus]

7 minutes ago, alex230ro said:

Poti sa faci loguri dupa loguri variatia e mica si nime nu nu va vrea sa riste sa schimbe piesa si problema sa nu dispara .In cazuri ca al tau nu exista - da e actuatorul schimbam si va fi ok .Repet am expieriente in care ziceai ca e un lucru doar ca sa descoperi  - ca de fapt e altceva . Deci bucura-te de masina si cand va fi mai grav iti va spune ea .

Îmi asum eu riscul asta, vreau doar pe cineva sa se uite pe date, sa spună ce alți parametri ar putea fi analizați si sa spună dacă ar putea ajuta o astfel de lucrare la masina sau nu. Sunt realist si nu ma aștept la garanții, sunt 100% convins ca este vorba de o piesa care este la limita tolerantei si din aceasta cauza este greu de diagnosticat.

Pe de alta parte risc sa dau mai mulți bani de diagnoza decât pe lucrare, dar cine știe, poate puțin câte puțin ajungem la o concluzie si găsim care este de fapt problema, in cazul in care nu actuatoarele vanos sunt problema. Și mie mi se pare ca nu cutia de viteze/transfer este problema, pe care m-am focusat pana acum, ci mai mult ceva legat de motor.

Edited May 16 by goangaus

[alex230ro]

La Vanos parca e si in clip ai target vs actual acolo vezi daca ai variatii ciudate , cauta un coleg cu diagnoza si iesi undeva pe DN/autostrada si testeaza .

Edited May 16 by alex230ro

[Ramid29]

@goangaus ai reușit sa iți rezolvi problema, un update ?

 

[goangaus]

50 minutes ago, Ramid29 said:

@goangaus ai reușit sa iți rezolvi problema, un update ?

 

Nu, nu am gasit nici un service dispus sa-mi faca datalog in mers, toți fac doar diagnoza in service si atat, doar ca stiu deja ca nu sunt erori. M-am hotărât sa schimb totusi actuatoarele decat sa stau sa tot fac diagnoze si analize si sa cheltuiesc jumatate dintre costul pieselor doar pe diagnoze, o sa merg in viitorul apropiat. Aveam de gând sa-mi instalez Ista si sa ma apuc eu de monitorizat dar am ceva dubii sa iau softul de pe torenți si sa-l conectez la masina, initial am zis ca nu o fi mare lucru, ce se poate întâmpla, dar la o căutare scurta pe net sunt cazuri de calculatoare brickuite de la o simpla scanare cu Ista, asa ca am zis pas.

Topicul era mai mult despre cata incredere sa avem in informațiile/hinturile date de ChatGpt, mie mi se pare foarte tare ca vine cu tetalii tehnice pe care le gasesti greu daca nu esti de specialitate, doar ca nu stiu cat sunt de adevarate.

Edited May 23 by goangaus