Any suggestions will be appreciated. I have a Daihatsu Hijet 998 which has failed the MOT on emissions, totally. Every measurement was off the scale. It has 57000 miles on the clock and has had a new head gasket fitted recently. The engine managment light has not shown on the dash. The garage that does my repairs has now run out of ideas as to what could be wrong!
It has had a new oxygen sensor fitted as he thought that might be at fault, but no. Now I have a new oxygen sensor. Rather than pile on the expense I now have the motor at home and am attempting to diagnose the fault myself. As of now I am in the process of ruling out any sensor related faults using an oscilloscope and waveforms for various components that I found on the net. I know I could throw money at it by changing the engine management unit but loathe to do so until I can say that is the problem.
If anyone can help me I will really appreciate it, thank you in advance.