Have a 1999 RX 300 and transmission is taking to long to shift, any suggestions, Does IAC valve have anything to do with it?

 

Nope, really only affects how it idles.

Is the fluid/filter fresh and clean?

 

fairly fresh fluid, but not the filter

 

Welcome to Club Lexus!

Reset the ECU, by pulling the battery cables for a few minutes. That should help.

 

Is your overdive on or off?

 

Thanks for the tip, I disconnected the battery overnight got better but is still very loud it shifts but is still noisy. Do you have any other suggestions? I did shut off the O/D did better.

 

Off for now.

 

Problem solved, Cat replaced and trans is behaving baby. However, found out that an exhaust mount needs to be replace it allows the cat to sit and prevents from moving freely. Does anyone know what am talking about? Looks like a motor mount but is by the exhaust and cat.

 

Like this? https://www.clublexus.com/forums/rx-...pipe-leak.html

Just got mine welded up last week, so far so good.

 

Just replaced the Cat on my 1999 RX300 . However I was having problem with the pickup and it was still struggling. Now I have the same code was P0420 Catalyste Sysytem Efficiency Beow Threshpld Bank 1 it also is says pending. Just paid over $200.00 for cat. Is it possible the NEW cat is bad?

 

That code is usually for the oxygen sensor after the cat. Usually the CAT isn't the issue. I had that code a year ago, and i fixed it by replacing the oxygen sensor after the cat with an oem dense one from amazon for only $65.

 

YeP replace that 02 sensor and that code should be gone.

 

Have replaced all O sensors (3) 2 cats and still having problem with car. Shift find from 1 to 2 gear however, as soon as I start going up an incline the car does not shift fast enough and then when it does, it starts to speed up and then slams into gear.

 

Thank you all but the problem has been solved! See attach diagram the third Cat down stream just before the muffer was the problem. "http://www.RockAuto.com"