my lexus RX300...developed this problem of jerking and gets worst if i engage reverse gear or turn on the air condition.The engine runs quite rough and its movements is quite dull with smelly smoke from the exhaust pipe atimes and often atimes i hear the engine running on high tune even when i remove my leg from the gas pedal leading to high engine temperature. i have changed plugs severally, changed fuel pump,i maintains regular change of my oil and filter.
can someone help me out with an idea as my mecho have ran out of idea to fix this problem.
THANK YOU ALL.

obilizy: my lexus RX300...developed this problem of jerking and gets worst if i engage reverse gear or turn on the air condition.The engine runs quite rough and its movements is quite dull with smelly smoke from the exhaust pipe atimes and often atimes i hear the engine running on high tune even when i remove my leg from the gas pedal leading to high engine temperature. i have changed plugs severally, changed fuel pump,i maintains regular change of my oil and filter.
can someone help me out with an idea as my mecho have ran out of idea to fix this problem.
THANK YOU ALL.

Have you car scanned to diagnose fault. No point changing parts, without knowing the faulty culprit(s)!!!