Thanks Hypervish and Salim,
These are helpful data points. I look forward to getting the actual specification and test conditions from Salim so I can apply them to my RX and compare the results.
I have done detailed measurements of idle rpm changes with varying loads on the engine to test various sensors and IACV performance. Quite interesting data (but pretty nerdy). If you're interested I can post my results.
Baetke

 

Hi Salim, thankyou again for researching and your prompt response.

1. The CEL light came on, i checked it was 0440 code which is for emission, so could be a loose fuel cap, but once i reset and take in for about 300 miles drive i dont see the light except in city driving. I had this way before i could open the intake manifold or the timing belts.
I changed the air filter and have new 6 NGK iradium plugs, all i did it my self after getting duped with Lexus/Toyota and some local mechanics.
yesterday i took the throttle body out to clean the butterfly since there was carbon formed around the butterfly valve. I got the valvoline carb/throttle body cleaner and planning it to do it this weekend.
I was comparing my lexus with my wifes Honda Odyssey and this morning i drove the Odyssey and it is still smoother with 110K miles on it vs the lexus started giving me problems right at 65K. Those Toyota Vehicles, I just hate them.

I torqued all the 4 bolts on the intake manifold so i dont think i have vacum leak there. Let me see after the throttle clean up, it should better, keeping my fingers crossed.

I also noticed that i have to constantly give gas to get the vehicle moving, once i take my feet off the accelerator it slows down immediately in decrease of 5 miles......

Car is not smooth as it use to be and like i said, if i drive above 1000rpm it is ok, but when i stop in D mode i feel the needle for rpm at about 400 to 500 rpm and the car is like sputtering/ vibration ( i dont know the right terminology to describe)

Please any advice.

 

Mines is a similar problem. N at 650 to 750, but on Drive idles at 400 to 500 RPM with a noticable vibration, change cyl 2 ign coil as i had a CEL for P0302 long back. I will also check the 3 spk plugs to see if they are burning or totally white tonight.

 

If city driving brings back p0440 ... then you need to get to the root cause. Your ecu will do funny things based on the inputs it gets.

Do you get 2250rpm at 60? If not then that would be an overdrive issue.

Vehicles have different roll based on their profile. Your tires can make a huge difference. Are you getting above 16mpg avg <= again this number can vary due to many things.

Salim

 

yes i get anywhere from 2250 to 3000 RPM based on 60 to 75 mph

I drove last friday to WV and my avg was about 19 MPG Avg, but i was not happy with the way the car was driving and felt it rough and dragging compared to my Honda 03 Odyssey. I drove my Odyssey to downtown today at about 75 mph and the rpm was around 2000 to 2250. Honda Odyssey has 110K miles and Lexus currently has around 99K miles. I have been trying all options and not able to get to the root cause of this vehicle. I think i may have to pop it out. instead of wasting too much time and go for any Honda vehicle aapka # milega ?

Thanks again Salim for your help and i do appreciate your time.
Mathew mathewd23@yahoo.com

 

We are doing apple vs oranges. Cant compare different vehicles. I am not trying to say which is better. RX will feel and behave differently. The gear-box is different and you will get get a different number for rpm - speed. Your mpg and idle speed seem in line with other owners.

If the P code comes on during city driving, then try to find out why.

Salim

 

Have not found the spec but here is another data point.

After driving around for about 1/2 hr (everything warmed up).
Trans in P.
Radio Off
Headlamp ON (high beam off)
Rear def On
Ac off
foot on the brake pedal
idle is at 750 <= eyeballed the gauge.

Salim

 

Thanks Salim. Here's the idle data I collected with my scan tool.

Car fully warmed up and in park and all accessorys OFF. The black line shows the engine rpm with the scale on the left side of the chart. The red line shows the IACV position with the scale on the right side of the chart. With no loads the car idles at 700 rpm and IACV is 14.5%. As I add in the various loads shown in the chart you can see how the rpm initially dips and then recovers to 700 rpm as the ECU opens up the IACV a little further. With all of the loads on, the IACV is open to about 23.5% but the rpm stays at 700, as it should. This is how I verify the operation of my IACV.

Baetke

 

At what ambient temperature did you perform this test? Just curious to know.

 

Engine temperature was 180F. Don't recall the exact ambient temp but it would have been about 45-55F in my garage.

 

Hi Guys, I am back again, sorry for asking too many questions, but i dont think i am able to fix the issue that i have and not knowing what to do, feel like pulling my hair out.
This is for my 2000 Lexus Rx300 with 99K miles.
This weekend i took the throttle body out and cleaned it with the carb/throttle body cleaner by using Valvoline product. checked the MAF and the IACV and cleaned both.

I took a small pipe and tried to hear any vaccum leak, but found none. Took the car for a test drive on highway and same issue, I need to continously accelerate to keep the car going or it just slows down immediately. I got a P0150 code which is a O2 sensor ie bank2 sensor 1 behind the radiator. I did replace this when i had purchased the car at 65K with a Denso and that was in 2008. Can this go bad in such a short time and only with 35K miles. I am confused. Could that be the problem for the highway driving. I also added SeaFoam to my fuel tank and always use Shell Gas 89. I also noticed some smoke in the morning when i start my car near the flexi pipe.

I need some help please to determine what is causing the car to drag on highway.

Thanks

 

Hi Salim,

The Code is P0440, i get it anytime and there is nothing to connect with what could generate that code. I checked it at Autozone and they told me it is emision or gas fuel cap. I replaced the cap with a new one, but did not help. I took it to toyota since I had a mechanic friend and he checked with his scanner and found no issues with Solenoid or Charcoal Canister. . Only thing i recall on this post that overfilling your gas tank can cause a canister to go bad, and i use to overfill it to round it to the nearest dollar, but that was around 6 mos back,

I also read that if i take the car for a long drive it will not come and i did notice that if i drive on a long drive, the code does not show up even after driving 300 miles or so, but immediately shows up once i am driving in the city

 

Mathew .. I tried to explain the 'slow down'/drag is not a problem as your mpg seems ok.

Do you have a code at this time ... your post indicated it come on during city driving... Have a competent mechanic fix this. Some of the evap codes are very hard to trace and can add up in labor charges.
search found this for me
https://www.clublexus.com/forums/rx-...ode-p0440.html
If it is the charcoal filter, you may have to replace it.

Your idle rpm seems reasonable, but you are feeling vibrations ... how bad and what is the condition of your engine mounts? This may be tied to your CEL


Visit a muffler shop and they can tell how to fix the leak.

Salim

 

Salim, Thankyou again for the advice and pointing me in the right direction. So let me put this in a bullet format to explain all the issues and summary of what was done on this car when i purchased it in 2007 with 65K Miles and want to avoid confusion.

1, Changed O2 sensor on Bank 2 Sensor 1 in 2008 when the car had 65K miles and now it came again at 99K miles, i did a reset yesterday morning and it did not come till now, does it needs to be replaced within a short span of 35K miles ?

2. I checked the engine mounts and they are good, like i said it is not vibrating too much and does not sputter if the car is above 1000RPM only a little bit like a misfire when the car is in D mode at the traffic light when it goes to 500RPM. The funny thing is there is no CEL for Codes P0300 to P0306 so i dont even know if my ignition coils are bad. I replaced all 6 spark plugs with brand new NGK irradium at 98K miles.

3. Since oil was leaking from the back Valve Cover and falling on to the Flex pipe, I think there is a leak in the flex pipe and i am thinking of taking it to a muffler shop and get the flex pipe replaced with a 2.25" and 6" long flex pipe.

Saiim Thanks for the link and i took a quick peek at it, in fact i have replaced the PCV (was clogged) , cleaned the MAF sesor and replaced the gas cap too when i took the intake manifold out, but my reason for P0440 is due to over filling of fuel in the gas tank which then goes to the charcoal canister to get burnt out, but that only happens if you drive on long drives, I had the same problem with my Honda Odyssey and i did take the car for a long drive to NY and it never came back.


I am not worried about the P0440 code or the P1150 code as i can take care of it. The only concern is when i drive on the highway i feel like car is not driving as it should be and need constant acceleration to keep it above the 65 to 70 MPH mark. I dont know what else to look for.

I will truly appreciate any help form the experts to get my problem resolved for the highway driving.

 

Mathew:

SUV are bad at high speed >65mph. It is the profile/drag issue.

If you pose the question as what is wrong with your RX ,,, the answer will be .. if your mpg is reasonable (which it is) then there is nothing wrong with your RX.

If you pose the question, how I can improve it .... then we need to look at tires. There is little you can do to the body profile and the only variable you can play with are the tires/wheel/inflation-level and tread-pattern. I am assuming you are driving with windows closed.


Salim