Poor hot starting

My 2001 Toyota Yaris 1000cc is very hard to start when hot. There is no problem when it’s cold and there here are no recorded fault codes. Mr Swerno

If you have the device to read off live data from the engine, this would be my first move. As the engine starts fine from cold and runs well, the most likely problem is the engine temperature sensor (ETC). If this is giving false information to the control systems it may affect the hot starting.

Another problem with some Yaris engines was carbon build-up that caused the valves to stick and reduce compression when hot, making starting difficult. Carry out a compression test to ensure this is not the case.

Finally, the crankshaft position sensor can cause a hot starting issue, but this usually leaves behind a code. injector pump but there was no change or improvement. I also got the car hooked up to a diagnostic scanner at a Toyota dealer, but no faults were logged. I have fitted a new turbocharger and have tried driving the car with the exhaust removed, but there was no change. I then took off the throttle body and checked the inlet manifold to see if coke had built-up, but it was fine. I was told that the intercooler could be clogged, but intercoolers were not fitted to this year of vehicle.

One unusual aspect of this problem is that if you drive the car fairly hard up through the gears, once it hits 26002700rpm, you can feel it pick-up and drive normally. However, once you go up to the next gear, the revs drop and the car is back in slowcoach mode. I took off the timing cover to ensure the timing had not jumped one cog, but it was fine.

Michael Carty