THis car came in for a regular service after which the car returned a week later with the MIL on and would slightly misfire intermitently at idle. The DTC mentioned above was read and deleted which returned a few days later. Firstly i believed this to be caused by an air leak so checked no pipes had been left off or rags left in the intake trunk, i found none visualy and a spray of carb cleaner around the engine made no change to the idle or engine note?
I checked the live data which showed the H02S1 switching correctly and the rear staying at around 438mv. When i checked the Maf reading at idle it showed around 4.4 g/s a little under the ESI spec of 6.5+.
I scoped the MAF and H02S1 during cruise both performed as expected but at snap throttle there was no initial peak from the MAF (went to about 2.6v) and during the rest of the WOT the 02 sensor dropped to 0v then back up to 0.8v so it was clearly underfueling during this period, what baffled me was the fact that if you hold the idle at around 1000rpm (normally 700) then hit the gas pedal you get a perfect MAF and 02 sensor trace? it seems as though either the MAF is undercalculating the air or something is stopping the engine from breathing properly? All injectors(Volts and current) checked as well as cleaning out the throttle body and EGR valve, also removed the 02 sensor incase the CAT was blocked which had no effect? Any ideas? sorry for the extensive post!also with the Solus pro the STFT fluctuated between 0 and -2