Before posting this thread I did some research and found some information, including a great tutorial by The Mole on how to clean your IACV (SC3):

https://www.clublexus.com/forums/per...rol-valve.html

My situation is this:

1993 SC400, 51,000 miles. I've never had a problem with it ... at all. The car runs like as new but has stalled twice in the last two days ... while it was moving. When started and warmed the car idles at about 650 RPMs (shouldn't it be 800 RPMs?) The stalls have occurred when I was releasing the gas pedal ... the tach showed a noticeable drop in RPMs at the time, down to about 300 RPMs. Some times, at a stoplight (while in drive) the idle will drop (consistently) as low as 4-500 RPMs.

My questions are as follows:

1) What SHOULD the normal idle be for a stock SC4 in park and in drive?

2) I know that this could very well be a dirty IACV ... but the engine only has 51K miles (and 16 years old). What is the most probable cause ... and solution.

3) the '93 SCs are OBD I. I have an OBD II scanner. Is the OBD II scanner backwards compatible ... and does the SC4 have the same port interface as a later (OBD II - equipped) SC?


Other than this one minor issue the car runs like a dream ... and if I continue to care for her as I have been should go (I estimate) another 50 years or more.

Thanks for all your advice ... and you too Mole.

 

check your spark plugs and wires... you can be losing power on the spark which may cause you to stall.

 

1)- mine seems to like 650 RPM's but it's hard to tell with the factory tach.

2)- My 92 just hit 59K, the other day the bodyshop hosed down the engine, causing a miss. Was gonna install new plugs anyhow so I swapped them and checked my factory wires, discovered 2 were way out of spec (like 45K ohms and spec is <25K Ohms). I swapped them all out with NGK wires and all is well. My plugs look well used by that point.

3) OBDII scanner won't work with car. I wish it would. A paper clip and read flashing codes. Assuming your CEL is on this should be done too.

Frankly, I would check the wires, and do the IACV cleaning, it's free to do this before you start throwing more parts and time at it.

 

I located a great link if you have an SC4 and your IACV requires cleaning:

http://www.planetsoarer.com/IAC/iac.htm