Toyota Premio D4 3S-FSE Engine

Has your "Check Engine" light come on?

Based on your description, I can only assume it has.

If this is the case, take it into a Toyota Dealer or any repair shop that can read the error codes.

This will remove all diagnosis speculation and guess work.

Yes the light has come on repeatedly and I took it to the car dealer whose diagnosis revealed that the censor was faulty. the problem did not stop despite changing the censor

Then the dealer didn't fix it. Take it back, demand satisfaction!!!!!!!!!!

Hey I'm having a similar problem but mine only manifest itself when I've been driving for about a hour. Which senor was faulty with your vehicle?

Welcome to the site. If you would start with year, make and engine, we would have a better chance of helping you.

There are two places that would cause your issue that are common. Both are air mixture at idle. First would be a vacuum leak, and the other would be the idle bypass solenoid. If the solenoid became gummed up from fuel deposits, then as the engine warms up fully, and wants to idle at its slowest speed, the solenoid MAY not respond quickly enough to maintain a proper idle speed, or the solenoid may have just failed. Have a competent mechanic read the stored trouble codes if your car is later than a 1996.

thanks for the welcome. i have a 1999 toyota corona, with a 3s-fse engine.

I checked the hoses and clamps and so i guess i can eliminate the vacuum leak. where would i locate the idle bypass solenoid?

The idle bypass solenoid is attached to the throttle body. It must open while at a "0" throttle position to allow sufficient air to enter the engine to maintain a steady idle speed when you do not have your foot on the throttle. When the engine computer sees the engine speed below what it thinks it should be, it opens the idle solenoid to allow additional air to increase the engine speed. When the speed is above the idle speed, the solenoid is not used, and all of the air for the engine passes across the throttle blade(s)

If you can not find your throttle bypass solenoid, you should pick up a service manual for your vehicle. Good luck.

I agree with KJK/USA.

Based on your description, your knowledge of vehicles seems limited. Instead of speculating, take it to a competent mechanic and have them fix it.

Would you try to pull your own teeth, or set a broken bone?

Take it to the man!

Sounds a lot like a vacuum leak. Check all vacuum hoses before spending any more money.

Besides the aforementioned issues, what about a clogged catalytic converter?

Clogged cats will cause an effect similar to a speed restrictor. It will run up till a certain speed, but no further. Think of trying to breath through a straw.

A misfiring spark plug could cause the symptoms described, but so could 25 to 30 other things. If the op paid for a diagnosis, he is entitled to a refund, or a better guess. JMHO.