Having some issues with my Passat (2000 V5 2.3L) as it does not really want to start when hot. No problem starting when cold but once the car warms up it can take up to 4 attempts to start it. Recently I have replaced the crankshaft sensor so that can be ruled out. VCDS does not really show any error codes on this. Are there any VCDS blocks that I could read that would reveal more of what the issue could be?
I had a similar issue with mine. The crankshaft position sensor does not always set a code when it goes bad. The temperature sensor is likely the culprit.
A coolant leak won't affect the Coolant Temperature Sensor as long as you have enough coolant to fill the system; in other words, the reservoir always has coolant in it. Another thing besides the temp sensor to look into are air leaks. The engine may start when cold, as the richer mixture commanded by the ECU may compensate for the extra air, allowing the engine to start. When hot, the ECU causes much less fuel to be injected, so an air leak can make the mixture too lean to light. An air leak such as this would also leave a fault code for fuel trim- mixture too lean.
Look at the coolant temperature in VCDS. The coolant temperature sensor is really two sensors in one--one sensor is wired to the temperature gauge, while the other is wired to the ECM. So, the gauge can be reading normally while the ECM is getting a faulty reading.
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