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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While stop engine idles like cylinder missing?

Common problem noticed on many car models.

Basically in this types of cases,you get steady check engine light on dash.The steady check engine light on dash is indication of error code stored in cars computer memory.

More than likely you have the beginning of an intake manifold gasket leaking. As this gets progressively worse the check engine light will illuminate and you will end up with cylinder misfire and a P0171 lean condition code. There is a new redesigned intake manifold gasket. This predominantly only happens when it is cold outside. This is easy to detect when you start the engine and when it is idling rough spray carburetor choke cleaner along the plastic manifold and the cylinder head surface. If its smooths out then you know is leaking. You also need to clean the mass airflow sensor. These are notorious for getting contamination on them. It will cause the vehicle to run extremely lean also.

This details will help.Thanks.

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