Hi Folks,

2002 Montero Ltd with auto box. It idles fine in P and N, but when I engage D, it starts to miss and run badly - never quite dies. When I accelerate, it misses a few beats before getting smooth. All fluids at right levels, plugs etc. quite recently changed. Any suggestions where to start?

Thanks,
Jon

 

My first instinct would be fuel system - fuel pressure, etc. It sounds like its not getting enough when under load. Easiest way to see this is to hook up a scanner with live data stream. Then you can see if there is a big chamge in fuel delivery when engine is under load (in D)

 

It seems likely that an idle fuel circuit is not delivering - the pump etc must be ok, because there are no signs of fuel starvation at high speed. How do I diagnose idle problems?