Reader Question Austin,
My son drives a 2001 Hyundai Sonata. Intermittently for the past six weeks, when slowing down to a stop, the car makes a loud, clunking sound. When accelerating from a stop, the car makes a loud, clunking sound, there is no power, and the engine light comes on, but the revs are up. We took it to a transmission specialist who diagnosed that the knock sensor needed replacing.
He replaced the sensor and changed the transmission fluid (which did need changing). The problem disappeared for 9 days and then re-appeared. My son was accelerating on a green light after stopping at a red light, and had to pull to the side of the road because there was no power.
The car behind him almost collided with him. We took the car back to the transmission specialist today to run some more diagnostics, but I am afraid this is going to cost us a fortune before the real problem is diagnosed and fixed. Please help. Thank you. Jennifer
I do agree with the first diagnosis of a bad vehicle speed sensor, and it is strange the vehicle was fine for 9 days after it was replaced.
I don’t know if I would think the sensor was the cause of the noise though, for that I would look at the engine and transmission mounts and see if one was broken. If the engine or transmission is banging about it could have damaged the sensor…and the new one.
You might ask them if they checked the mounts, especially if they say the new sensor is bad…..something had to cause the new failure. It COULD be possible that there is an internal problem in the transmission…..but try to rule out the more obvious items first.
Let me know what you find out.
Austin C. Davis