I had been experiencing a hesitation under part throttle from 1500rpm to 3000rpm. During start up it would take longer than usual to come out of cold start mode. Gas Mileage was not good, well worse that usual, and tail pipes are now black and I have been burning oil about a liter every 2 weeks. I will save you the details of parts I changed (most should have been done as maintenance at this many KMS, 207000kms) As I was scanning I noticed the ecu would kick it in to open loop under part throttle and the hesitation was between 1500-3000rpm and at 3000rpm the car would go into closed loop kick and drive normal. Coolant temps were in spec and went up in 1 degree increments, in spec as it should (during the warm up period). Some of you are asking why is the car in open loop? good question it should not be under these conditions. That was the issue, the car would go into open loop when it was not supposed to causing all kinds of issues. Problem was the coolant temp sensor. I will have to take it through a few drive cycles before I get excited but for now the hesitation is gone and the car is hitting the Lambda targets and going into open/closed loop as it should.

FYI Coolant temp sensor not fun to get at. The plastic retainer clip is almost sure to break so if you are doing this as DIY project get a clip and save the headache.