Hello everyone, I need help on a VW Polo 9N3 1.4 BBZ.
The engine suffers from severe spark knock/pinging under load (around 2000 RPM) and runs excessively hot.
Here is the live data from OBD (Car Scanner):
• Long Term Fuel Trim: -23.4% at idle.
• Short Term Fuel Trim: -6% at idle.
• Engine Coolant Temp: 95°C cruising at 60 km/h, climbing up to 104°C in city traffic.
• MAP Sensor: Reads normal, 36 kPa at idle.
The radiator fan 1st stage seems not work, it only kicks in at 103°C. I have already replaced λ sensor, radiator, water pump, and thermostat twice. The throttle body has been cleaned.
What could be forcing to pull 23.4% of fuel, lean condition and knocking under load? Could a wrong fuel filter or a faulty EVAP/EGR valve? Any insights on what is the problem would be highly appreciated!
Pinging noise and hot engine 1.4 BBZ
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iichel
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Re: Pinging noise and hot engine 1.4 BBZ
With LTFT at -23%, the ECU is pulling fuel, so the data points to a rich condition or the ECU being fooled into thinking it is rich, not a lean condition.
If it has been running rich for a while, carbon/soot build-up on the piston crowns and combustion chambers is possible. That can create hot spots and contribute to pinging under load. But I would treat that as a consequence, not the root cause.
Pull the spark plugs and inspect them. If all plugs are black/sooty, look for a global rich cause such as excessive fuel pressure, wrong fuel filter/regulator, coolant temp sensor, MAP/IAT issue, or EVAP purge stuck open. If only one plug is black, suspect an injector on that cylinder.
I would verify fuel pressure first, especially if the fuel filter/regulator may be wrong.
If it has been running rich for a while, carbon/soot build-up on the piston crowns and combustion chambers is possible. That can create hot spots and contribute to pinging under load. But I would treat that as a consequence, not the root cause.
Pull the spark plugs and inspect them. If all plugs are black/sooty, look for a global rich cause such as excessive fuel pressure, wrong fuel filter/regulator, coolant temp sensor, MAP/IAT issue, or EVAP purge stuck open. If only one plug is black, suspect an injector on that cylinder.
I would verify fuel pressure first, especially if the fuel filter/regulator may be wrong.
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RUM4MO
- Bling Bling Diamond Member
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- Location: Mid Lothian
Re: Pinging noise and hot engine 1.4 BBZ
My first thoughts are, the air/oil separator is letting too much engine oil through into the inlet area. You might find that your engine is using oil and if so, that would confirm what I'm suggesting.
Also, the pinging/knocking, if what I'm suggesting is true, is being caused by the oil which is not a good fuel, sort of diluting the effective Octane rating of what is ending up inside the combustion chambers - and so the knock resistance is a lot lower than it should be along with the "energy coefficient" of the fuel being used.
I seem to remember that Pierburg provide a suitable oil seperator to replace your original VW Group one - which might even be made by Pierburg.
I've been there done that with a 2002 VW Polo with the lower output BBY engine, the pinging/knocking even in low temperatures had become too annoying, changing to using 97 RON petrol mainly stopped that, but at a price. The oil usage was also a nuisance but I had come to believe that all VW Group petrol engines "liked a bit of oil" - my only other VW Group car experience at that time was my 2000 VW Passat 4Motion with the 2.8 V6 30V Audi engine.
Replacing the oil separator was the very last thing that I did to try to improve things, and it did, although my wife preferred to keep using 97 RON petrol as that improved the drivability of that BBY engine, which frankly should never ever been fitted to that age of Polo as it minimised everything - low power, low drivability and low miles per gallon - a proper turd of an engine even when new!
Also, the pinging/knocking, if what I'm suggesting is true, is being caused by the oil which is not a good fuel, sort of diluting the effective Octane rating of what is ending up inside the combustion chambers - and so the knock resistance is a lot lower than it should be along with the "energy coefficient" of the fuel being used.
I seem to remember that Pierburg provide a suitable oil seperator to replace your original VW Group one - which might even be made by Pierburg.
I've been there done that with a 2002 VW Polo with the lower output BBY engine, the pinging/knocking even in low temperatures had become too annoying, changing to using 97 RON petrol mainly stopped that, but at a price. The oil usage was also a nuisance but I had come to believe that all VW Group petrol engines "liked a bit of oil" - my only other VW Group car experience at that time was my 2000 VW Passat 4Motion with the 2.8 V6 30V Audi engine.
Replacing the oil separator was the very last thing that I did to try to improve things, and it did, although my wife preferred to keep using 97 RON petrol as that improved the drivability of that BBY engine, which frankly should never ever been fitted to that age of Polo as it minimised everything - low power, low drivability and low miles per gallon - a proper turd of an engine even when new!