I think VVT adds another variable to it. The cams are advanced and retarded and could change idle speed too.

 

I had the same problem on my old 1995... I found the problem was exacerbated after a long drive and when pulling off the highway the car would die. I cleaned out the throttlebody and found it to be much better and the stalling quit.

FYI... I just did the IACV delete onmy 1998 when I replaced the power steering pump, but don't recall if it made much difference. It had already fried the alternator before I bought it. And yes, the power steering vacuum lines are at least the same on my 1998.
Don't underestimate the impact of cleaning out that throttle body.

 

How did you delete it? There is no IACV for a 98.

 

Oops. I meant the power steering air control valve on the ps pump

 

I understand now. Initially I wondered why you wrote that since I always find your posts are quite nice and informative.

 

I have an 06 Lexus GS300 that had the Lexus GS & IS Engine Misfire Recall CSP performed in 2012. Last year I noticed that in hot humid weather with the AC on, my idle began fluttering. Since it only happened a few times last year, I wrote it off as a fluke. This year however, the RPMs dropped to 500 or below, triggering the infamous "Check VSC" and "Check Engine Lights". I used a bluetooth code reader and noticed that the car was throwing engine misfire codes in addition to P0505 Powertrain Idle Control System codes. My first thought was that the car needed to have the carbon buildup cleaned again, whcih would costs thousands at the dealership. Luckily, I found people with electronic throttle bodies saying that once they cleaned theirs, the problem was fixed.

Well to make a long story short, I decided to clean my electronic throttle body myself, even though there's been reports of people breaking their $700 throttle bodies in their attempts to clean it. I recorded the whole process, for my youtube channel and of course for Club Lexus members Enjoy, I learned a lot from the process, including scaring myself to death when the butterfly door didn't seat properly.


BTW: I have a whole Lexus Service playlist on my channel which includes dealer footage of the carbon cleanup CSP.

 

Thanks Jayjw!, I had a same problem with low idle speed, I will try swapping hoses by tomorrow

I will give you update

Team Ls400 lol

 

Years late, but ill try this one out. My 95 UCF21 has been giving me fits. Next resort is getting the IACV cleaned and replacing TPS and MAF. Already rebuilt the ECU, wish that had been the problem haha.

 

here is another helpful link to checking out the IACV:
https://planetsoarer.com/IAC/iac.htm