MattLS400

Cowboy, as outlined, I have carried out the above and my RPM is 400 at Normal Operating Temperature( For my Car this is At the 50% or half temp gauge mark )
What could possibly explain my RPM dropping so low when the engine temperature reaches this mark?

N.B--please note that at the 40% mark of the temperature gauge, this rough idling problem and shutting off does not exist.

fixmiester

Put a scan tool on it that has live data feature; see if the rough idle ocurrs when the system goes from open loop to closed loop. Then you can look for the real cause.

MattLS400

Thanks Bud..Cowboy, does your recommended scan tool have the live data feature ? From your thread:
https://www.clublexus.com/forums/ls4...uld-spend.html

Odzsee

Hi MattLs400,

I had the same problem. The solution is very simple.--> Throttle body cleaning.

My problem: A/C compressor off when engine warm, because it is too low idling. A/C compressor on when runing engine.

I was thinking that we could be in trouble. Idle RPM warm-->450 Too low.

I look my throttle body. Butterfly valve is very dirty. I cleaning my throtle body, thereafter RPM 650 and A/C compressor not off.

Steps:

1. Battery negative cable take off. !!!!Very important!!!
2. Cleaning throttle body.
3. Waiting 30-40 minutes. The engine computer must forget the old/bad RPM.
4. Battery negative cable take on.
5. Automatic transmission--> "P" and running the engine.
6. Let the engine run for 30 minutes. Do not give me gas, automatic transmission olny "P" position. (This engine computer learning time)
7. Enjoy the new 650-700 RPM.

This repair very cheap.
I hope I could help.

shanjam

simple auto choke on when cold ,auto choke off when at right temp.if car is not lumpy leave alone

MattLS400

Hmmm interesting Odzsee...... I have done this a couple times to reset the ECU....It runs smooth for a while, yet it goes back to the same problem....

But, question as to why it may not be throttle body cleaning....>> The problem only happens when the Engine is warm (Half Temp)...Therefore, if it were a dirty Throttle Body/ Butterfly issue, won't the problem persist all the time, irregardless of when the engine is cold/ hot?

MattLS400

Hmmmm....some good food for thought there Yamae....Thanks!

I have made videos of the problem being experienced on this car. How can I upload these videos ?

Yamae

400rpm is too low. Why don't you simply remove the IACV from the throttle body and check the air passage located at the center part of it. The attached drawing might help you. I'm sure it is badly clogged and you need to clean it.

When the car is warmed up and the IACV is almost closed but still passing thorough some air for the idle, the clogged passage limits the amount of it. This must be your situation, I bet.

At the idle, the engine needs about 50g/sec of air but the clogged passage can't pass through that much. Yours must be passing only 35g/sec or so, according to the calculation.

PureDrifter

iTrader: (10)

Clean throttle body, don't overcomplicate the first step of troubleshooting.

L8274Jones

Ok Guys There is another Temp sensor in the system This is right next to the Gauge sensor This one has Two wires and talks to ECU It can also be bad and If so tells the ECU the engine temp wrong info and can confuse the situation .... If it is bad and tells ECU engine is clod still it Affects Mixture ie it runs rich always and your gas mileage suffers too !!

L8274Jones

Sensor I bought Online True Blue Auto Parts Beck?Arnley #158-0421 $23.65 Free Shipping
I renewed both these sensors as cheap Insurance to get proper info to me and the ECU

http// trueblueautoparts.com

timmy0tool

iTrader: (7)

a good link to fixing a IACV for those interested.
http://planetsoarer.com/IAC/iac.htm

LScowboyLS

yes, that is the best fix for Idle air Control Valve!

if anyone needs the original correct IACV bearings brand new made in Japan - PM me

LScowboyLS

those two sensors are so critical in my book that I go with strictly Toyota on those!

MattLS400

Yamae and Puredrifter, Thanks Ill surely do that. My IACV was serviced and was inspected to verify whether or not the clicking sound was present to ensure it was working. The sound was present. However, this was not inspected at the temperature I experience my problems ( Half temp). IPreviously, didnt know that the IACV operates differently at different temperatures. More fingers are pointing towards a clogged IACV...the further below is a link to the video of my problem...

L8274 I am now being informed of this. I have changed my Engine Coolant Temp Sensor to OEM 89422-20010.....Now you're telling me there's another which should have been changed ? Thats weird, I was never informed that there are 2 ECTS...Please, send me a link for this other Temp sensor and where is it located?


Members,
the following is a link to the video of the Problem I am experiencing with my 1996 Celsior (1UZ-FE)