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[Solved] Bmw e90 320i N46B20 Engine Strokes between 1200-3000rpm Post Sea Trip: Diagnosis and Experience

Saimon46 41166 16
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Why does my BMW E90 320i N46B20 knock between 1200 and 3000 rpm, and what part should I check or replace?

The knocking was caused by a broken spring in the VVT/Valvetronic mechanism under the exhaust shaft, and replacing the damaged spring(s) solved the problem [#17403356][#17403540] Before that, the thread also considered adaptations, the vacuum pump, and even the air filter, but those were not the real cause [#17218181][#17219964][#17226452] One reply specifically pointed out a broken VVT spring visible in the photos, and the original poster later confirmed that one of the four springs had snapped [#17403356][#17403540] After replacing it, the engine returned to normal operation [#17403540]
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  • #1 17218116
    Saimon46
    Level 8  
    Posts: 14
    Rate: 16
    Hello, gentlemen, the problem began in my e90 320i N46B20 in my room two weeks ago after leaving the sea distance of 600km after parking and re-ignition, you can hear metal bands under the cover between turns 1200-3000rpm I will add the most gas after gasification after even gas much less. return visit to the BMW check engine zero errors and the diagnosis of the workshop replacement of the pneumothomy Ok pneumothy complete new and continue tapping (on cold does not start after 3-5 min) I will add the day before I replaced the filter on the KN and the next day knocks. Oil always the same BMW TWIN TURBO 5w30 LL04 Orginal candles in Bmw 10tys ago took oil before replacement odmie occasionally smoked on the lights any ideas Thanks
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  • #2 17218181
    chiqi
    Level 10  
    Posts: 37
    Help: 2
    Rate: 19
    Are the adaptations deleted?
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  • #3 17218201
    Saimon46
    Level 8  
    Posts: 14
    Rate: 16
    I do not know, but I will ask you tomorrow and ask if you can explain what these adaptations are and when I do it I live in Spain so I will go to the Dealership tomorrow and I will ask. I will add that the zero revolutions engine works smoothly on 7L 110- 140km / h zero problems with firing the perfect power
  • #4 17219382
    karp23
    Level 15  
    Posts: 86
    Help: 7
    Rate: 25
    probably a shaft on the shaft
  • #5 17219402
    Saimon46
    Level 8  
    Posts: 14
    Rate: 16
    I do not really know where to start compressing the engine ... I have no idea if I can drive it?
  • #6 17219964
    sebap
    Level 41  
    Posts: 7139
    Help: 538
    Rate: 1076
    I would not risk it.
    Was not it the problem with the head lubrication in these engines?
  • #7 17220007
    Saimon46
    Level 8  
    Posts: 14
    Rate: 16
    Damn I wonder if it did not affect that on the same day I put a KN filter maybe too much air gets stupid
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  • #9 17220124
    Saimon46
    Level 8  
    Posts: 14
    Rate: 16
    And tell me this thing, whether the vacum pump can wear with gas, because when I open the oil stop I have a dull knocking
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  • #10 17226452
    Saimon46
    Level 8  
    Posts: 14
    Rate: 16
    Well, there is a diagnosis from the vacuum pump that dzyndzel flew what goes into the fight tomorrow new Pierburg pump new oil 5w30 Motul filter and see Mechaniol friend Moroccan says he does not see anything there is a fight valve says how tomorrow ufff I will write 3 pics .
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    #11 17403356
    piotreks86
    Level 11  
    Posts: 12
    Help: 2
    Rate: 10
    In the second and third photo I see a piece of broken spring vvt under the exhaust shaft: o
  • #12 17403379
    helmud7543
    Level 43  
    Posts: 12621
    Help: 1216
    Rate: 1563
    Adaptations are adjustments to the factory dosing maps of the fuel and air mix. They are made when there is a suspicion that they have disappeared. The vacum pump may also knock, although the description fits the pan - you are lucky. These engines were not really blurred on the shaft. Worse as valvetronik is falling apart - renovation here will be expensive and it is a typical fault of this engine. The engine has the right to work badly after opening the oil plug (depending on the engine - drop in speed, increase in speed, knocking) - finally the left air gets.
  • #13 17403540
    Saimon46
    Level 8  
    Posts: 14
    Rate: 16
    Well, the problem was solved by colleague Piotreks86, he noticed that one of the four springs snapped and from this place I started setting 4 new Motul 5w30 oil for the complete timing and the Ceratec LM filter and KN air filter ... believe me not auto change the work of accelerating the voice 180 degrees !!!!
  • #14 17404828
    piotreks86
    Level 11  
    Posts: 12
    Help: 2
    Rate: 10
    Well, that's the problem. In my VVT I mentioned the servomotor and the shaft with cams which were not the worst, but I did it when replacing the suction shaft which was worn on 1 cyl.

    What filter did you put on exactly? Is there a difference in the engine work / sound?
  • #15 17404834
    Saimon46
    Level 8  
    Posts: 14
    Rate: 16
    The filter is the KN E2021 I recommend to anyone without fairy tales to feel the differences more willingly rides and sounds more racial
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  • Helpful post
    #16 17405068
    piotreks86
    Level 11  
    Posts: 12
    Help: 2
    Rate: 10
    Thanks. I will buy some for sure because I changed the oil yesterday and withheld the filter. I was still thinking about Simot.
    What is the advantage of K & N over other brands in addition to the company?

    So that there is no OT, there is no flow in the N46 engine in the E90 model, so the use of such wet filters is safer than in flow cars.
  • #17 17433436
    Saimon46
    Level 8  
    Posts: 14
    Rate: 16
    Ok, as I have already pIsalem, the problem is over, so I close the topic.
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Topic summary

✨ The discussion revolves around a BMW E90 320i with an N46B20 engine experiencing abnormal metal tapping noises between 1200-3000 RPM after a long sea trip. The owner reported that the engine runs smoothly at idle and higher speeds but exhibits knocking sounds upon acceleration. Initial diagnostics showed no error codes, and a replacement of the pneumothomy was performed without resolving the issue. Participants suggested potential causes, including issues with the vacuum pump, lubrication problems, and the impact of a recently installed K&N air filter. A broken spring in the variable valve timing (VVT) system was identified as the root cause, leading to the replacement of the springs and oil, which significantly improved engine performance. The K&N E2021 filter was noted for enhancing engine sound and performance.
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FAQ

TL;DR: In this BMW E90 N46 case, 1 of 4 Valvetronic springs failed—"one of the four springs snapped"—causing a top‑end tap; replacing the springs and timing restored smooth power. [Elektroda, Saimon46, post #17403540]

Why it matters: For BMW E90 320i N46 owners and techs, this FAQ speeds diagnosis of post‑trip or sudden top‑end tapping and points to proven fixes.

Quick Facts

What’s the most likely cause of top‑end tapping on an N46?

In this thread, the proven root cause was a failed Valvetronic spring. The owner reported “one of the four springs snapped.” Replacing all four springs and refreshing the timing eliminated the tapping and improved acceleration and sound. Start by inspecting the Valvetronic hardware before assuming bottom‑end issues. [Elektroda, Saimon46, post #17403540]

Is it safe to keep driving with the tapping noise?

No. Park it and diagnose. A mechanical valvetrain fault can escalate to major damage if you continue driving. As one member put it, “I would not risk it.” Transport the vehicle to inspection rather than running it. [Elektroda, sebap, post #17219964]

Could a failed vacuum pump cause similar knocking?

Yes. The N46 vacuum pump can knock and imitate valve‑train sounds. “The vacum pump may also knock,” noted a contributor. Inspect the pump for play or internal damage before committing to cylinder‑head repairs. Replacement is straightforward and a useful elimination step. [Elektroda, helmud7543, post #17403379]

How do I check or reset ECU adaptations after intake or timing work?

Adaptations are the ECU’s learned fuel/air adjustments. Reset them after intake or timing changes so the ECU relearns correctly. “Adaptations are adjustments to the factory dosing maps of the fuel and air mix.” Use a BMW‑capable scan tool to clear them, then road‑test. [Elektroda, helmud7543, post #17403379]

Did the long 600 km trip cause the problem?

The noise appeared right after a 600 km sea trip and a restart. That links the timing of onset, not causation. Use the trip detail as context, then diagnose the valvetrain and vacuum pump to find the actual fault. [Elektroda, Saimon46, post #17218116]

What exactly fixed the OP’s car in the end?

Replacing the failed Valvetronic spring set solved it. The owner installed four new springs, refreshed complete timing, changed oil to Motul 5W‑30, and added LM Ceratec. He retained a K&N panel filter. The engine’s response and sound improved markedly after the repair. [Elektroda, Saimon46, post #17403540]

I opened the oil cap and heard dull knocking. Is that normal?

Yes. Opening the oil filler cap introduces unmetered air. RPM can drop or rise, and noises can change. An expert explained it clearly: the engine may “work badly after opening the oil plug… finally the left air gets.” Refit the cap and reassess. [Elektroda, helmud7543, post #17403379]

Why are there no fault codes even with loud tapping?

Mechanical issues in the valvetrain may not set diagnostic trouble codes. In this case, the ECU reported zero errors despite a clear tapping noise. Investigate mechanical components when symptoms persist without codes. [Elektroda, Saimon46, post #17218116]

Which K&N filter fits the E90 320i N46?

K&N E‑2021 fits. The owner reported a crisper throttle and sportier intake sound after installation. If you use an oiled filter, follow the cleaning and re‑oiling instructions precisely to maintain performance. [Elektroda, Saimon46, post #17404834]

Should I revert to the stock air filter when diagnosing?

Yes. A/B test by refitting the previous filter to isolate variables. A member advised, “try to put on an old one.” This helps confirm whether intake changes affect drivability or sound. [Elektroda, chiqi, post #17220014]

Are N46 engines prone to camshaft wear or Valvetronic failures?

A contributor noted camshaft wear is not typical for these engines. Valvetronic failures are a known fault and can be costly to repair. “Worse as valvetronik is falling apart—renovation here will be expensive.” Prioritize Valvetronic checks for top‑end noise. [Elektroda, helmud7543, post #17403379]

Is there a head‑lubrication issue behind this symptom?

Not in this case. The investigation did not find a lubrication defect. The confirmed failure was a snapped Valvetronic spring, addressed alongside a timing refresh and oil service. Focus on Valvetronic hardware first. [Elektroda, Saimon46, post #17403540]

How can I triage N46 tapping before running it again?

Do a quick staged check:
  1. Inspect the vacuum pump for play/noise and replace if suspect.
  2. Remove the valve cover; inspect Valvetronic springs for breakage.
  3. After repairs, clear ECU adaptations and road‑test. These steps isolate common causes fast. [Elektroda, helmud7543, post #17403379]

Is K&N better than other brands on the N46?

This thread offers no comparative data. It only reports that the K&N E‑2021 felt more responsive and sounded sportier. Choose a filter you can service correctly and that fits your maintenance routine. [Elektroda, Saimon46, post #17404834]
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