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For the last couple of days I noticed that my short term and long term fuel trims have elevated severely at idle. In the past values were around 0 to +3% now they are above +10% which indicates there is a problem (running to lean). When driving a while I noticed that the fuel trims return to more acceptable levels (around +3% and lower LTFT).
This seems like a classic case of a vacuum leak. I have checked under the hood but could not hear any hissing or find a broken vacuum line?
I have checked my mass airflow rate (~98kPa @ wot) and manifold pressure while driving and it seems like the mass airflow rate is rather low @ around 50/60 g/s @ wot (should be around 72 for a 1.8L).
Update: Tried again pulling through WOT at German autobahn and I was able to reach 72 g/s around 4000rpm.
Though I must say that I recently filled it with E10 fuel (normally E5), and I know that E10 could make fuel trims positive but by this much?
Since yesterday I added injector cleaner in the tank and filled it up again with E10 (half a tank) but my fuel trims are still abnormal positive. Anybody know where to diagnose further? Idle After a decent drive
