When driving steady with tach at 3000 rpm engine RPM will drop suddenly to 1000 RPM and than suddenly return to 3000 rpm while keeping steady pressure on the accelerator. This happens at any speed or RPM and the transmission does not shift correctly and will not go into passing gear when accelerator is fully depressed. I just recently had the timing belt replaced by your group so that should eliminate that. The car needs the Valve Cover Gaskets replaced but need to resolve this before I do that. I have sprayed carb cleaner on the engine trying to find a vacuum leak and found none.
My car has 122000 miles.
My car has an automatic transmission.
Hi there. It’s quite possible that this issue is directly related to the transmission or torque converter on your Hyundai Sonata. In many cases, the slipping RPM is caused when the transmission slips into a higher gear (like the 3000 to 1000 RPM issue you described). This can be caused by low transmission fluid or perhaps a damaged internal hydraulic line inside the transmission. It could also be as simple as a shift sensor or other electrical components. Before having any repairs completed, it would be best to have one of our mobile mechanics complete a car is hard to shift inspection. The key thing to remember is if you book this service, please ask the mechanic to test drive the Hyundai with you to attempt to replicate the symptom, as this will give them a better clue as where to begin the diagnostic work.