Sounds like the point where it switches from Open Loop (equivalent to choke on carby cars) to Closed Loop.
In closed loop, the engine switches to using all the engine sensors to maximise engine efficiency.
The behaviour your describing is most likely an engine issue.
I'm thinking it may be the MAF sensor.
On conventional automatic transmissions on modern cars, the ECU and TCU work together to optimise shifts in the transmission. To do this smoothly, the ECU needs to know how much torque the engine is producing at any given moment. It uses the MAF for this.
An out of spec MAF will not throw a code unless it fails completely. It merely gives incorrect air flow readings which leads to incorrect fueling and rough shifts.
You may also be noticing higher fuel consumption, though it won't necessarily be noticeable.
SOURCE: benimur
Hi,
To my understanding, on an Audi A4, error code P1392 indicates camshaft sensor circuit. This could be a faulty sensor the camshafts are not correctly timed. 90s Audis are not very common in my country but from what I can gather:
The mark for the crankshaft gear is on the cover you have to remove in order to get at the timing belt. The sprocket you may be having trouble with is the intermediate shaft (in front of the water pump) and I don't believe that one matters at all since it doesn't drive any of the cams. The intake cams are driven by a chain off of the exhaust cam shaft so only the exhaust cam is driven directly by the timing belt.
Additionally, you may benefit from the Audi A4 Service Manual and/or Audi A4 Cabriolet Workshop Manual.
Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.
Good luck and kind regards. Thank you for using FixYa.
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