when your vehicle starts getting lower gas mileage or the engine hesitates when you press the accelerator.
however, these above symptoms are also related to other issues like dirty throttle body, spark plug failure, fuel pump failure or dirty fuel filter.
imho, injector cleaning should only be done when all of these issues are resolved.
on how much, no idea though, but i heard servitek alabang does that for 1,500 for sedans. have not tried it though.
gano katagal? siguro mga two hours the most.
for diesel engine, the best that you can do is diesel purging using liquimoly diesel purge. maganda yung direct feed yung diesel purge to injection pump to clean the injectors.
google mo lang, daming instructions online. if ayaw mo mag DIY, meron ganyang service si PowerTorq. 950/can yata diesel purge + 500 labor.
I have searched liquimoly here at davao, but not able to find one, also talk to them via their FB page, and they said they have no seller here, not sure if there are private seller, in case you able to find one, please inform me, I will DIY the cleaning.
Have you tried putting 2T oil? mixing it on your Diesel fuel. I have done on alternate basis.. minimized the nginig. Forgot to mention it on the other thread.
For cleaning injector, I asked one diesel injector calibration center at Cabaguio, cleaning only, 100 pesos per injector, if my memory is not wrong, but there might be additional if they found some thing that need to be replace since they are going to remove the injectors.