2006 Prius seems to lose power, hesitate, or temporarily stall while coasting
I always come here if my 2006 Prius (165,000 miles. original owner) has any issues. Almost 100% of the time, I walk into the dealer and tell them what I've read the likely issue is, and this forum has ended up nailing it. This time, I couldn't find anything that sounded exactly like what I was dealing with. I took the car in 3 separate times, over 6 months, and kept being told there were no codes and they couldn't get the problem to duplicate. Finally, I got the big red triangle of horror, so they had to spend some real time and effort diagnosing. It took 24 hours, and communication back and forth with Toyota head office I guess, to figure it out. So I thought I'd share what happened in case anyone else has the same issue:
1. Around 155,000 miles, the car started "hiccuping" at infrequent/random times. The best way I can describe it is by saying it felt like I was hitting a large pool of water. The car would quickly lose power/speed but almost instantly return to normal. No lights, no warnings. Any passengers with me never even noticed.
2. Over the next 2 months, the hiccups became more frequent. I was able to figure out that they occurred most often while I was keeping a constant speed. Didn't matter if it was 35 or 75, cruise control or not. In a 25 minute ride to work, the hitting water sensation would happen a dozen or more times. They seemed to be slightly worse when the car was started after sitting for several hours, but never stopped even when driving after an hour or more.
3. It got to the point that I was worried the car would completely stall on me on the freeway, so I had to drive in the outer lanes for quick escapes to a pullout just in case. Hiccups became obvious enough that passengers could tell when they were happening. I told the dealer after my third fruitless visit for help that I would just have to drive it until it died on me.
4. The car finally gave out its warning lights (a mile from home on a quiet, side street thank goodness!) At first, all they could get the codes to say was that the engine had "failed to start." Toyota headquarters weren't really able to help. They started replacing suspected parts with spares from the garage to see if it would clear the issue. Nope! A technician took the car out again, once again hooked to the diagnostic computer, and had it completely stall on him as he exited off a ramp. The diagnostic computer stopped recording everything about the car, which they said they couldn't understand. This time though, when they got the car back to the dealer, the internal code indicated Throttle Body failure. Whoo hoo! Finally, something to work with.
Really long story short: ordered a new throttle body, installed it, and the car runs perfectly again. Back to 48+ mpg, $1375 poorer, but incredibly received my car runs safely again.
So, while I hope no one else has to go through this nightmare, I also hope it might help anyone facing the same problem get things fixed more quickly.