The vehicle was completely serviced and checked and all replacement parts replaced!
My hunch is that it is the o2 sensor! This is a lean burn engine, with a 4 wire o2 sensor. It is extremely dependent on the feedback from this sensor under light throttle conditions, when in lean burn mode and I guess it is running too rich or too lean at the time!
After about 50% throttle, there are butterfly valves in the intake runners switching it from 12 to 16 valve operation. Then the car seems to run fine.
The worst part is that this engine will not run with any other 02 sensor!
@KKOOL, sir g could you please help in finding the correct o2 sensor for this engine (7A-FE LEAN BURN)?
Part # for these sensors starts with 89463-XXXXX
Cheers