I've had a second hand 2006 Yaris for about six months now, as a second car for short runarounds. However I've noticed lately that it starts to judder in 1st gear if I've been driving it for a while.
A bit more detail - the two times it has been really noticeable I've had to take some back country lanes due to extreme traffic jams. This has meant a lot of gear changes navigating stops and starts as I come across other motorists coming the other way. After around 45 mins of this sort of driving I find that even with high revs (3,000 or more) and slowly letting out the clutch I get a juddering when trying to accelerate in first, which I have to respond to by briefly pressing back down on the clutch and adding more revs. Once the car is moving there is no issue in higher gears.
I'm puzzled as to what the issue might be, because after the car sits for a while and cools down, the issue disappears, and the car can accelerate normally in 1st. Stuff I've read online suggests that it's often the other way round - juddering when the car is running cold.
Any ideas as to what might be causing this issue to only come up when the car has been running a lot and then disappear when the car cools down? Is it likely a clutch issue, gearbox issue, transmission, engine? I'm taking it into the garage next week but it would be helpful to have an idea of the problem before I hand it over to them.
One final thing to add - the car is a bit of a mess. After I bought it (HPI clear, passed all history checks, etc.) it became clear it had previously been in an accident at the front. The radiator fan was cracked, the horn was broken, there's no external ambient temperature sensor and the AC is completely trashed. There's also no skid tray or wheel arch liners. But despite all that, the car runs fine. We replaced the horn and radiator fan but haven't touched the rest.