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Toyota Repair/1998 Camry: 1MZ (V6 engine) idling problem


Hello Ted,

I have 1998 Camry with the 1MZ (V6 engine).  It has an idling problem which initially seems to indicate a faulty IAC Valve but the symptoms that my car has are different from other IAC Valve problems that Iíve read about.  Iím trying not to over think this but at the same time, I donít want to go through the trouble and expense (>$200 in parts alone) to replace the IAC Valve unless I have reasonable evidence that it is bad.   

First of all, cold starts are always fine.  The problem is with warm or hot starts.  After a successful cold start and warm up, I can turn off the ignition then restart the car and it will idle around 500 RPM (too slow for safe operation).  It will stay this way forever until it is driven.  After driving for about five or more minutes and reaching a stop, the car will return to its normal 900 RPM idle range.

When the engine is idling normally, I can short TE1 and E1 on the Data Link Connector 1 and the engine will idle up as it is supposed to.  When the engine is NOT idling normally, shorting TE1 and E1 has no effect.

Per the Factory Service Manual on page EG2-544, I checked for continuity between RSC (Rotary Solenoid Closed) and ground and RSO (Rotary Solenoid Open) and ground and measured continuity at both test points.  

Before removing the IAC Valve as suggested on page EG2-545, I measured about 6 VDC from RSC (Rotary Solenoid Closed) and ground, when the car was idling normally.  When the car idled slowly, I measured about 7 VDC.  I could not get a VDC measurement for and RSO (Rotary Solenoid Open).  I also donít know if this is supposed to be a variable signal or if it should be either 0 VDC or 12 VDC at RSC (Rotary Solenoid Closed).  Any thoughts?

I find it difficult to believe that the IAC Valve is faulty as it operates normally for miles but it does not malfunction until after a warm start.  I see that the VDC signals for the IAC Valve are controlled by the J/B No. 2 EFI Main Relay but it seems to me that a relay would either provide 12VDC or none at all.

Not sure where to go from here.  Do you think the IAC Valve could be bad but just suddenly start to work after a few minutes of driving?  Do you think that the IAC is not getting enough VDC?
I would appreciate any insight that you could provide.

Thank you for your time,


Hello, have you tried just cleaning the throttle body? If not give that a try firstl remove the intake hose and thoroughly clean the opening past the throttle plate using a stiff brush and a can of intake air cleaner, disconnect the battery while doing this after that drive the vehicle as usual and let me know if there is an improvement.

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Ted Ritter


I have more than 28 years experience as toyota technician, I will be able to answer most questions related to the Toyota product line up to the present year models,I am located in the US but welcome questions from other regions of the world. When asking a question please provide specific information: year,model, engine,transmission information. Provide as much information as possible including a brief repair history if possible. I have been a volunteer here for more ten years an have answered over 16,000 questions helping Toyota owners with their problems and save thousands of dollars without any compensation, some of my answers are published on many other websites including google and various automotive forums. DONATIONS ARE VERY MUCH APPRECIATED, IF YOU HAVE RECIEVED HELPFUL INFORMATION PLEASE MAKE A DONATION. AS OF TODAY (JULY 22, 2014) ALL REQUESTED GRAPHICS, ILLUSTRATIONS, DIAGRAMS, PHOTOS, WILL REQUIRE THE MINUMUM DONATION UP FRONT.


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