Skoda Fabia 2 1.2 2009 Engine Check Light, Cold Start Vibration, Misfire After Spark Plug and Coil Replacement

User question

Auto: skoda fabia 2
Egine check light continue
Pojemność: 1.2
Model 2009
Hello everybody,
I own a skoda fabia 2 2009 with petrol engine 1.2; i buy this car few months ago and.
Right now i am facing engine starting shaking and vibration problem while cold engine stafting
When i start car in first morning engine to much shaking missing and vibration for few second also engine yellow light on the display
I already change spark plug engine coil etc
Plz help me what is the accueal problem

Artificial Intelligence Response

Direct answer to the question

• The rough running and strong vibration you feel for a few seconds after the first cold start are almost always a cold-start misfire.
• On a 1.2 l 3-cylinder Fabia II the typical root causes – listed in order of probability – are:

1. Incorrect air-fuel ratio at start-up (vacuum leak, faulty coolant-temperature/MAF/MAP sensor, dirty throttle body).
2. Fuel-delivery problems (injector partly blocked, low fuel pressure, stale petrol).
3. After-market LPG system interfering with petrol injection (if fitted).
4. Minor engine-mount wear (adds vibration but does not switch the MIL on).
5. Mechanical issues (low compression, timing-chain wear).
   • Replacing plugs and coils was a good first step; now read the stored OBD-II codes and follow the diagnostic plan below before buying more parts.

Detailed problem analysis

1. Misfire logic in the ECU
   • At every start the ECU enriches the mixture and monitors crankshaft speed variation.
   • If the mixture is too lean/too rich or one cylinder fires late, rotational speed fluctuates ⇒ vibration ⇒ misfire counter exceeds threshold ⇒ MIL (yellow engine light) turns on with a P03xx or mixture code.

2. Typical Fabia-specific failure patterns
   a) Coolant-temperature sensor (ECT) – sends “engine already warm” to ECU → mixture too lean for a cold start → 2- to 5-second stumble.
   b) Small vacuum leak on purge/PCV hose under the throttle body – leak closes when rubber warms up → symptom only when cold.
   c) Throttle body varnish – plate sticks slightly open, upsets idle correction during enrichment phase.
   d) 3-cylinder injector fouling – engine often run short distances, one injector drips overnight → over-rich on first firing stroke → misfire flag.
   e) Timing-chain stretch (HTP engines > 150 000 km) – cam/crank correlation out by ≈ 1 to 2 °CA → cold idle unstable; usually accompanied by rattle.

3. If LPG (Stag 4 etc.) is installed
   • LPG ECU sits in series with petrol injectors. A bad crimp or a leaky LPG injector can give exactly the same cold-start misfire.
   • The quickest elimination test is to pull the LPG main fuse overnight and start in petrol mode only.

4. Why engine mounts rarely cause a MIL
   • Worn mounts increase perceived vibration but do not create misfire data – therefore they seldom turn the yellow light on. Replace only after electrical / mixture faults are cleared.

Current information and trends

• VAG service bulletins (2021-22) list ECT sensor drift and throttle-body contamination as the top two reasons for cold-start MIL on the CGPA/CGPB 1.2 HTP engines.
• Ethanol content in modern E10 fuels accelerates injector varnish; many workshops now perform on-car injector cleaning with polyether-amine (PEA) fluid instead of ultrasonic bench cleaning.
• Independent VAG specialists increasingly use cylinder-pressure oscilloscopes to confirm early timing-chain stretch before dismantling.

Supporting explanations and details

• Expected sensor readings with a scan tool on a stone-cold engine (should match ambient):
– ECT ≈ 10 – 25 °C, IAT within ±3 °C of ECT.
– MAP at key-on ≈ 98 kPa (sea level), drops to 28–32 kPa at idle.
– MAF 2.0–3.5 g/s at 850 rpm warm.
• Fuel pressure at the rail: 3.5 bar (key-on prime), should stay > 3.0 bar during crank.
• Compression (dry) 10–12 bar, max spread 1 bar – anything less when cold may signal valve-seat regression (another known 1.2 HTP issue).

Ethical and legal aspects

• Do not clear codes solely to pass inspection; fix the underlying emission fault.
• If LPG is fitted, many countries require the gas system to be inspected and certified after any repair – release the vehicle only with valid documentation.
• Observe battery disconnection procedure (air-bag data loss) when probing wiring.

Practical guidelines

1. Retrieve and list all DTCs (use VCDS, ODIS or any EOBD tool).
2. Freeze-frame: note coolant temp, rpm, load when the code was set.
3. Live-data cold-start test – watch ECT, MAP/MAF, STFT/LTFT.
4. Smoke-test the intake; repair leaks.
5. Remove intake hose, clean throttle body with non-residue cleaner; perform “Basic Setting 060” (throttle adaptation) in VCDS.
6. If misfire is on one cylinder (P0301-03): swap that injector with another, see if the code follows.
7. Still unresolved and > 120 000 km: measure cam/crank correlation or pull top cover to inspect chain free-play.
8. Only after misfire is gone decide if engine mounts need replacement.

Potential challenges:
• Frozen plastic connectors break easily on a 2009 car – warm the engine bay or use connector-release tools.
• Intake leak may be under the battery tray (hard to see) – plan for 1–2 h labour.

Possible disclaimers or additional notes

• The advice assumes a stock 1.2 HTP CGPA/CGPB engine; if your car is a 1.2 TSI chain-drive turbo the sensor values differ slightly.
• Without the exact DTC numbers any recommendation is probabilistic; always verify with live data.

Suggestions for further research

• Investigate VAG technical bulletin 15-20-10 (“ECT circuit cold-start rough run, Fabia/Polo/Roomster”).
• Follow current studies on valve-seat wear in small 3-cylinder indirect-injection engines at high ethanol percentages.
• Examine open-source firmware logs (ME7.5/ME17) to better understand misfire monitors.

Brief summary

Your Fabia’s cold-start shake is nearly always a mixture-related misfire.

1. Scan for codes, look at coolant-temp and fuel-trim data.
2. Fix any vacuum leak or faulty ECT/MAF sensor.
3. Clean the throttle body and, if needed, the injectors; verify fuel pressure.
4. If an LPG kit is installed, isolate it during diagnosis.
5. Only then consider engine mounts or deeper mechanical faults.
   Approaching the problem systematically will save parts, labour and repeated yellow-light frustrations.

Disclaimer: The responses provided by artificial intelligence (language model) may be inaccurate and misleading. Elektroda is not responsible for the accuracy, reliability, or completeness of the presented information. All responses should be verified by the user.