2 Attachment(s)
2.0 FSI Poor idle when cold
After my daughters Golf left her stranded for a while Ive swapped my trusty SAAB for her dubious Golf :eek:
Ive got most things sorted out from door locks to faulty light switches, broken wires etc. But I am stumped on this one.
When starting from cold.
fires almost straight away revs shoot up and drop to around 1200RPM where it stays for almost exactly 30seconds, duringing this time the idle is lumpy and will on occasion miss fire a number of times but not always. If you try to drive off in this time - you just dont it drives terrible.
after the 30 secs idle drops down to around 800RPM and smooths out considerably and all is well. Although it it could be better but its not bad.
stop the engine and restart and idle almost imdeiately settles at around 800RPM and is relatively smooth.
This occurs both in the morning when its cool around 17deg or so and the afternoon when its around 30deg.
VCDS scan shows
Nox sensor Low flow (this only shows up after going for a drive)
MAP thermostat open circuit
Evap flow issue ( because in hunting for a solution I found the evap purge valve to be open all the time. I have plugged the pipe to stop the leak while I wait for a new valve to arrive)
Here is a couple of graphs Ive made from the VCDS logs which show the issue nicely the dodgey section is the first 30 secs the second rise in the idle speed at around 40 seconds is me intentionally raising the RPM to around 1200 to see what effect that has on timing etc.
The low manifold vacuum and extreme timing retardation is what stands out to me but the question is why?
Attachment 42865
Attachment 42866
I had been looking for Vacuum leaks and found a couple - Evap purge solenoid and the PCV tubing which I have plugged with no noticable change.
The 30 second duration seems to be possibly the length of time the ECU runs in MAP mode before changing over to a closed loop mode and taking care of the problem.
Ive been continually frustrated by the lack of information about the non turbo variant of the FSI motor - if anyone can point me to some detailed documentation or offer some ideas I would be very greatful.
Im thinking perhaps it is a sensor giving bad data but with limited detailed documentation it makes it a bit tricky. Everything Ive seen just refers to VAG Self diagnostic procedure xyz.....
THE VAG self study articles are great for an over view but thats about it.