IAC problem

Tiny
GSMS1968
  • MEMBER
  • 1999 LEXUS RX 300
  • 3.0L
  • 6 CYL
  • AUTOMATIC
  • 94,000 MILES
The car would not idle very well about 400 rpm's. I cleaned the IAC valve and got lots of carbon out of the unit, but now it idles at 3200 down to 1500 and over and over I ran the air conditioner and it stays at 2500 or a little less. I cannot get it to go any lower. It has 12.4 volts key on and a good negative to coil. I unplugged the IAC and it did not lower the rpm's. I can remove the coil and manually operate IAC valve to desired idle. I am assuming it needs to re learn, but I tried for a hour or more with no luck.
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Monday, May 23rd, 2016 AT 7:19 PM

4 Replies

Tiny
HMAC300
  • EXPERT
Clean the throttle plate on both sides as well and check for a vacuum leak or cracked hoses etc. If it continues scan for codes. Most auto parts do for free.
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Tuesday, May 24th, 2016 AT 6:28 AM
Tiny
RENEE
  • ADMIN
Hi Gsms1968,

Here is a link to an article that features written step by step instructions and pictures explaining how to do the scan yourself, also I have included a link to our YouTube channel with a how to video on code scanning. Most scanners are inexpensive to purchase, you can purchase one online from sites like Amazon.com. Once you have the codes please get back to us so that we can further assist you. We are always happy to help.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

https://youtu.be/YV3TRZwer8k

Thank you for visiting 2CarPros.com.

Kindest regards,

Renee
Admin
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Tuesday, May 24th, 2016 AT 1:13 PM
Tiny
GSMS1968
  • MEMBER
Thank you I have a scanner it only had a knock sensor code. I am sure its picking up due to the low rpm rattle that the engine was doing. There are no cracked hoses and lines that I can find. I cleaned the inside of blades and IAC valve and they are all clean as I can get. I did notice now if I unplug the IAC it will idle down to the correct rpm. Confused, Im having my friend bring over a scope to see if it is sending a signal to IAC coil this week.
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Tuesday, May 24th, 2016 AT 6:56 PM
Tiny
RENEE
  • ADMIN
Please come back and post your findings.

Renee
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Wednesday, May 25th, 2016 AT 12:49 PM

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