Hi I have a auto 99 4 cyl that can't maintain a constant rpm. e.g. coasting then accelerate to desired rpm and it will suddenly drop by 200-400 rpm with a low to moderate load, labouring the motor slightly. It drives great for 230k kms (cambelt done at 206) and after doing the usual service oil,fuel/air filter,plugs and leads,ATF/diff oil recently I'm all out of ideas.