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High idle after idle air control valve change

Tiny
DRAKMNSTR
  • MEMBER
  • 1999 LEXUS RX 300
  • 3.0L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 152,000 MILES
I replaced IACV valve on my vehicle listed above. The job is pretty straight forward. I replaced it with a brand new part from eBay. The part looked just like the one I removed. The price from from the original was very different. The eBay part was much cheaper.
I started the vehicle and the Rpm's were very high at 2100 Rpm's. It Rpm's would eventually get down to 1100 but would have a tendency to go higher after car was driven. I checked for vacuum leak at least 7 times. I used carburetor cleaner, propane, and water. All lines look fine. I removed the electromagnetic motor which is the black piece. I swapped it out with old one. I knew that one was working fine. Same issue with Rpm's. I must also note that I leaned throttle body well when it was removed. I cleaned mass air flow sensor. I used a brand new gasket when placing throttle body back. Rpm's drop but very slowly when I depress accelerator. Car drives with no hesitation but I do noticed that I get that additional surge one stopping due to Increase in Rpm's. The Rpm's should be around 750.
So I am stuck with this Rpm issue. I tried the idle relearn procedure and reset the ECU. This did not work. I do not think the battery has nothing to do with the high idle. I can hear the idle control valve open because of the high wine but settles down a little. I am
not sure what to do. Any advice?
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Monday, October 7th, 2019 AT 7:29 PM

8 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,336 POSTS
Welcome to 2CarPros.

Honestly, I have no idea what brand part you got. Often times the parts are very inexpensive and poorly made. (Not always but often) Now, I do need to know what the symptoms were prior to replacing the IAC. What prompted you to replace it? Were any codes pulled related to the IAC?

I realize you checked for vacuum leaks. However, check to see if the PCV is stuck open.

Let me know.

Joe
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Tuesday, October 8th, 2019 AT 6:40 PM
Tiny
DRAKMNSTR
  • MEMBER
  • 4 POSTS
Hi Joe,
I removed the hesitation on acceleration. I cleaned it as per you tube videos. The IACV was built up with carbon. I did use carburetor cleaner and it was better than new. I am not sure I did a great job and the hesitation started again on a relegation. I removed the black piece and the magnet broke off IACV. I had buy a new one. I decided not to by a pre own one. EBay had new ones for about thirty dollars. I was skeptical but tried it. The IACV moved freely and no leaks once I used an original Lexus gasket. The car dives but it does not rev low like it use to. The Rpms do not drop when releasing the throttle when in park or neutral. There are no codes. I have an obd2. I was going to try something I read on your site. I was going to remove electromagnetic Plug aka black piece, and see if it starts. I did recheck a week ago for freedom of movement of IACV and it was flawless. It move with no difficulty. It does not rotate 360. That would indicate something was wrong with the valve. There is also one more thing that I will check. I do recall two vacuum hoses going into a small plastic box. I will forward pictures regarding this and location. PCV was replaced when I did a tune up on vehicle.I did remove it and shook it. It appears valve is working fine but I will recheck that again. I will also give you a short video on start up. Car still drives well! Thanks for your reply and I will recheck.
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Wednesday, October 9th, 2019 AT 7:19 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,336 POSTS
Welcome back:

Let me know what you find. Also, if you can upload the video, I would like to see what is happening.

Joe
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Thursday, October 10th, 2019 AT 6:13 PM
Tiny
JIS001
  • MECHANIC
  • 3,408 POSTS
Hello and welcome to 2CarPros. I wanted to jump in here because of the Ebay part. When an idle control valve cost a couple hundred dollars vs. $30.00 then there is going to be issues. At this point I would say install the OE part and let's go from there.

If you came in to a shop they would tell you the same the thing. The inferior part needs to go to properly diagnose from there. If you have the old part I would recommend you put it back and then have professional look at it. Just my thoughts.
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Saturday, October 12th, 2019 AT 12:41 AM
Tiny
DRAKMNSTR
  • MEMBER
  • 4 POSTS
Hi JISOO1, thank you for your reply. I went back today to Everything out. I even pulled the electromagnetic piece out. Check engine came on as expected. Car started and Rpm's were higher than ever. IACV moving freely with no problem. I may purchase a real authentic IACV but I checked it before I put it in. SEEMS exact but of course I am no expert. I will show three videos. Thanks for looking.
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Sunday, October 13th, 2019 AT 9:43 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,336 POSTS
Welcome back:

As mentioned, I worry when aftermarket parts are used for specific types of repairs. Tell me this. When you replaced it, was everything where it mounts clean and carbon free? Also, have you tried cleaning the throttle body? When you had the throttle body off to replace the IAC, are you certain it was resealed properly and there are no vacuum leaks?

Here are the directions specific to your vehicle for replacing the IAC. Take a look through them to make sure everything was done.

1999 Lexus Truck RX 300 AWD V6-3.0L (1MZ-FE)
Removal and Installation
Vehicle Powertrain Management Fuel Delivery and Air Induction Idle Speed/Throttle Actuator - Electronic Service and Repair Procedures Removal and Installation
REMOVAL AND INSTALLATION

pic 1

COMPONENTS

REMOVAL

1. REMOVE THROTTLE BODY

pic 2

2. REMOVE IAC VALVE
Remove the 4 screws, IAC valve and gasket.

HINT: At the time of installation, please refer to the following items. Place a new gasket on the throttle body.

INSTALLATION
Installation is in the reverse order of removal.

_____________________________________

Let me know.

Joe
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Sunday, October 13th, 2019 AT 8:01 PM
Tiny
DRAKMNSTR
  • MEMBER
  • 4 POSTS
Hi Joe,
I purchased an original OEM and a throttle body that had only 41000 miles on it. The price was to good to pass up. I removed the bLack piece to clean because I knew it may have a lot of carbon and possibly may be sticking. It was. After replacing the throttle body, Presto! Car idles fine. You were correct about the low cost parts. OEM will never let you down!
I attached a short video. I did clean it with throttle body cleaner. All good. Thank you!
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Wednesday, November 13th, 2019 AT 6:18 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,336 POSTS
Hi:

That's great news. I'm glad you got it going properly. Honestly, aftermarket parts for general repairs are perfectly fine. However, when you get into more involved and sophisticated components, it's easy to get something that just doesn't work properly. It's actually frustrating. There was a time that aftermarket parts were excellent. However, we now import things from places I never even heard of. LOL

Regardless, it's great to hear it's fixed, and even better, you found an OEM part for a good price.

Take care and feel free to come back anytime.

Joe
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Wednesday, November 13th, 2019 AT 6:23 PM

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