[Sigurd]

You read right. I have lost just over 10mpg on my normal trips.

I have been battling P1128 (long term trim too lean) issues for about a month. I could clear the code and get an extremely rough idle for awhile, until the short term trim maxed out at 25%. Then it would run okay. 10 miles later, the long term trim would set at 23% and the car ran wonderfully. City trips around 34, idle at 0.25 gph.

Last night, I popped the hood and found that I had either bumped or never reconnected the PCV valve to the intake. I reconnected that and took it for a drive. Started right up, smooth idle, smooth acceleration. Then I took a look at my UltraGauge. Short term trim is hovering a few percent around zero (good). Long term eventually has set itself around 3%. Idle gph is now 0.38 and my city trips are at 24. Even my 60 mile cruise on the highway got me 26 instead of 35.

Has the ECU just not relearned its stuff after driving with an intake leak for so long? Any ideas on what could have gone wrong?

98 Jetta 2.0L. I currently do not have any codes.