1999 Lexus RX300: Engine idles low and stalls in morning?

The Engine idles very low while start up in the morning.Also a stalling is noticed.
But once the engine warms up is starts and runs fine.


In this types of problem there are several possible causes for low idle/stalling when engine is cold - low fuel pressure, vacuum leak, faulty coolant temperature sensor, faulty Throttle Position sensor, faulty mass air flow sensor, sticking throttle body throat plate.

To find out which of the above is the cause, you will need to leave the vehicle overnight with a shop so that they can test it with a diagnostic scanner when cranking the next morning and engine is cold. They wont be able to test it after having driven straight to them as the engine will be warmed up and nothing will show as wrong.

If you are going to do the testing, you will need to do it first thing before its being driven and will need a fuel pressure gage, a voltmeter and scan tool to test the above mentioned possible causes.

These details will help.
Thanks.

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Idles at low rpm and will not rev up?

This problem is faced by many others too.
First check out this.
If you remove the air intake tube and turn the key on to the run position and get a helper to press the throttle pedal does the throttle plate open?

If it opens, then --
Disconnect the negative battery cable and wait 5 minutes then reconnect. Now with the air intake tube still off get some one to start the car and watch the throttle plate. If it starts it will run rough. If it starts then have them apply throttle and see if it will rev up. If it will not rev up then the electronic throttle body is faulty. If it revs up then reconnect the air tube and disconnect the battery once again to clear the computer of any faults you caused by running it with the air intake tube disconnected.

But if it revs up by this procedure then, throttle body is faulty.