2004 Audi A4 1.8T BEX starting issues and running rough

[Dan A4 1.8T]

Hey all, hoping someone can point me in the right direction to repair my 2004 Audi a4 1.8T. Problem I’m having is hot or cold intermittent hard starting (cranks and won’t start first time but always starts on second or third attempt) code was P1128 Lean bank 1. I have changed both Coolant sensors, spark plugs, fuel filter, maf sensor, front 02 sensor and tried a new purge valve. No difference. Strange thing is with the new lambda sensor im getting P0130 code and it keeps coming back straight away after I clear it. The rough running almost feels like a misfire worst around 2500rpm. What else could it be?

[Darepoole]

Are you sure the oxygen sensor you replaced is the bank 1 sensor?


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[Dan A4 1.8T]

Yes front pre cat sensor, strange thing is I was never getting a code for 02 sensor before I changed it but was advised by mechanic the lean code was either maf or pre cat 02 sensor after changing both of them the car is running no better and now has the P0130 code 02 sensor circuit malfunction bank 1 sensor 1

[Darepoole]

If you have vcds log 030, 032,033. If you don’t have vcds do an ohm reading on the sensor. If it’s not a genuine Bosch sensor it may be defective. Aftermarket sensor can be hit or miss


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[Dan A4 1.8T]

I don’t have vcds I have a snap on modis ultra, what should the reading be for the sensor functioning properly? It is a Bosch maf and a Lucas 02 sensor

[Gin+]

Kinda sounds like crank position sensor. Does the tach bounce when it's cranking over but not starting?

[Dan A4 1.8T]

No bounce it just turns over as normal but won’t start, once started it sometimes idles like there nothing wrong next time it’s lumpy. Anyone know what the 2 coolant temp sensors should be reading, also 02 sensor readings so I can check live data? Also any idea if there’s common pipes to look at for vacuum leaks?

[Gin+]

Let me rephrase, if the motor is turning over but not starting, and you don't see any movement on the RPM gauge, you could have a bad crank position sensor. If the ECU can't sense the motor rotating it won't send any fuel or spark.