Bad Idle

[mamun22s]

I had a Toyota Clavia VITZ 2000 VVT-I 1.3L 2NZ-FE car. For the last few years it had a idle problem. Sometime all on a sudden it had a high idle like without pressing the accelerator it runs 25~35 Km speed. Then I adjust the throttle cable. after few days it starts low idle and car stall on low speed driving then again I have to adjust the throttle cable. One of engineer ask me to change the throttle but after change I face the same problem. I also check all the air pipe and found lo leak there.

[YarisSedan]

Id suspect a defective/stuck/clogged idle air control valve. If your remove the rubber boot that goes to the throttle body you can see several small holes inside the throttle spray some carb cleaner with straw down there and let it soak for a few minutes and while your in there clean the throttle body open butterfly and spray a bit of carb cleaner and reach in with a rag and clean as much of the black carbon and gunk that you can. reassemble and get ready to keep your foot on the gas for a little bit when you try to start it to blow out the carbon out of the exhaust afterwards it should run a lot better and smoother. If no change it may require replacement of the idle air control valve typically this corrects the issue and cost little to nothing.

[mamun22s]

Thank you for your answer. I had change the full butterfly with iac. it runs good for 3 months. Now the problem starts again. Sudden high idle and Engine start heating.

[mamun22s]

Can any one let me know the function of the parts and what happen when it's defective.

[BLOODY_STONE]

clean the MAF sensor and the air intake manifold .. i think that is the issue