I have a 2001 Toyota highlander that has 52000 miles on it. Recently when the engine is cold but it's like 70-80 degrees outside, when engine is first started and accelerator is pushed down lightly while in park it revs normally but if push down considerably the engine delays or hesitates and its like its almost going to backfire for 1 sec then revs up if repeated same thing until it is warmed up alittle. The same thing happens if I jump in and drive. Is this normal? Its never done this over the winter, is something wrong or is this normal? Air sensor? fuel filter? If no ideas, please direct me to a appropriate toyota forum Can't find a good one from google. Well maintained Oil change and air filter replaced at right times. Thanks Jonathon
Jonathan, I'm going to assume the check engine light has not come on? If it has, the dealer can pull codes with a scantool and that will help immensely with diagnosis. If the light has not come on there are a few possibilities. 1-in some areas oxygenated fuel is used during the winter months to help lower emmissions. This fuel doesn't like cold starts in warm weather and can cause drivability problems like what you describe. 2-If the engine has been steam cleaned or pressure washed recently, moisture can get down into the sparkplug tubes and cause spark jump on cold starts when there's lots of condensation inside the tubes. 3.-one or more of the ignition coils may be weak. 4.-possible vacuum leak causing overly lean condition when cold before engine goes into closed loop. 5-dirty throttle body. I tend to want to go with an ignition problem when engine cutout and near backfire are reported. Another thought--when you start it cold with ambient temp 70-80 degrees does the engine catch quickly and rev up to maybe 1600-2200 rpm then drop to about 1200 during initial warmup, or does it start and almost die or idle slowly? If the latter you may have a bad Intake Air Control valve (IAC valve) which is the device on the bottom of the throttle body that bleeds in extra air on cold starts to give you fast idle. Your best bet may be to leave the vehicle overnight at the dealer or good independent Toyota specialist and let them experience it.
