FAQ
TL;DR: Many Polo 1.4 TDI AMF vibrations trace to balance‑shaft chain wear (150–200k km). "Stretched chain offsets the balancer and causes vibrations." One owner reported less vibration after replacing the set at 170,000 km. [Elektroda, sigwa18, post #17336269]
Why it matters: This helps Polo 9N AMF owners quickly diagnose 1400–2000 rpm hum and avoid unnecessary parts swaps.
Quick Facts
- Symptom band reported at 1,400–2,000 rpm; at 90 km/h in 5th it can be unbearable. [Elektroda, rowerek0987, post #17328153]
- AMF 1.4 TDI reported without a dual‑mass flywheel. [Elektroda, rowerek0987, post #17328153]
- Flex‑pipe (“braid”) leaks raise noise; replacing it made the car quieter but didn’t cure vibration. [Elektroda, rowerek0987, post #17335508]
- Balancer chain/tensioner wear around 150–200k km can offset the shaft and cause vibrations; replacement reduced them. [Elektroda, sigwa18, post #17336269]
- Typical cost for chain+tensioner job: ~PLN 800–1000; parts ~PLN 400–450, plus seal and sump/strainer service. [Elektroda, sigwa18, post #17336441]
What causes my Polo 1.4 TDI to hum and vibrate at 1400–2000 rpm?
Worn balancer‑shaft chain and tensioner can misalign the shaft. The stretched chain and worn shoes offset the balancer and induce vibration. One member replaced the set at 170,000 km and felt a clear reduction. "Offset balancer shaft, which leads to vibrations." Start here if you’re near 150–200k km. [Elektroda, sigwa18, post #17336269]
Does the AMF 1.4 TDI have a dual‑mass flywheel (DMF)?
No. An AMF 75 HP owner reported this engine does not use a dual‑mass flywheel. [Elektroda, rowerek0987, post #17328153]
Can the clutch disc torsional damper be the culprit of this humming?
Yes, owners raised the clutch disc damper when shifts clanked and the engine felt different with the pedal pressed. First‑gear engagement felt hard with a knock initially, then normal on the second try. Consider the damper if these shift symptoms accompany the 1,400–2,000 rpm hum. [Elektroda, rowerek0987, post #17330061]
Should I replace a cracked or leaking exhaust flex‑pipe (“braid”)?
Yes. A leaking braid increased noise here. After replacement, the car became quieter, yet the core vibration persisted. Fix the leak to cut noise, then continue diagnosing vibration sources. [Elektroda, rowerek0987, post #17335508]
How do I correctly set the engine mounts to reduce vibration?
Seat the mounts under load before tightening. How‑To:
- Leave mount fasteners loose.
- Start engine, nudge slightly forward/back, hold half‑clutch.
- Tighten all mount fasteners.
This aligns mounts and can reduce transferred vibration. [Elektroda, berthold61, post #17335997]
What is the thickened section on the right driveshaft?
That tubular thickening is a vibration damper. It reduces driveline vibrations transmitted to the body. [Elektroda, berthold61, post #17335997]
How can I cheaply check injector balance on the 1.4 TDI?
Use a low‑cost KKL interface to read unit‑injector corrections. It costs about PLN 20 and shows plus/minus deviations. This quick check helps rule in or out fueling imbalance. [Elektroda, berthold61, post #17328256]
Could the air‑filter housing cause pedal vibration?
Yes. A bent filter‑housing bracket can let the canister hit the brake pump, making the bulkhead rumble and pedals vibrate. "The air housing sometimes hits the brake pump." Inspect and re‑seat the bracket before deeper engine work. [Elektroda, sigwa18, post #17336269]
How much does a balancer chain+tensioner service cost, and what else should be done?
Expect roughly PLN 800–1000 for the job. The chain and tensioner set runs about PLN 400–450. Replace the cover’s front seal and inspect the oil pan and strainer during the service. [Elektroda, sigwa18, post #17336441]
Where is the balance shaft, and how hard is inspection on the AMF?
Inspection requires significant disassembly. You must dismantle the engine to access the balancer chain and related hardware. Plan workshop time and tools for this job. [Elektroda, invisibleman, post #17336236]
When did a chain replacement reduce vibrations in this case?
One report noted the replacement at 170,000 km. After the chain and tensioner were replaced, vibration decreased significantly. [Elektroda, sigwa18, post #17336269]
Is 90 km/h in 5th supposed to be smooth on a healthy 1.4 TDI?
If you have this issue, some report it as unbearable at 90 km/h in fifth. In this thread, the owner also found a broken flex‑pipe braid. [Elektroda, rowerek0987, post #17328295]
What if I ignore chain/tensioner wear and misalignment?
The balancer remains offset, which directly sustains the vibration. You will continue feeling the hum within the problematic rpm range. [Elektroda, sigwa18, post #17336269]
Was the vibration problem ultimately solved in this thread?
No. The balancing shaft was checked and reported OK, but the car was sold with the issue unresolved here. [Elektroda, rowerek0987, post #17362438]
