1998 Lexus LS400 idling problems

[Phill 67]

I have Lexus ls400 1998 that has inconsistent poor idling. I believe this may be an ecu issue. Is there an ecu repair service that you’d recommend? Thanks

[messi]

It could also be sparkplugs or coilpack, and no they won't throw up a check engine light 

[Phill 67]

Thanks

 

[Phill 67]

Have you had any ecu issues yourself ?

 

[ambermarine]

It may be the engine coolant temp sensor which throws up this condition, a easy fix. If the ECU was giving problems you would get it over other dynamics of the engine running process. 

[Mihanicos]

Try cleaning the Mass Air Flow sensor.

Clean or replace the fuel filter. Check the fuel pressure and clean the fuel injectors.

Add fuel injection cleaning and maintenance fuel additive to the fuel tank.

Make sure the fuel cap has a good rubber sealant and no air can be drawn into the fuel tank.

Check the fuel canister for leaks and all its rubber tube connections are sound.

Chris.

[Phill 67]

Thankyou for your input/advice I appreciate it, but I really am trying to source anyone who tests the ecu ,it’s proving impossible

 

[shanra]

On 7/29/2021 at 10:47 AM, ambermarine said:

It may be the engine coolant temp sensor which throws up this condition, a easy fix. If the ECU was giving problems you would get it over other dynamics of the engine running process. 

This is what was causing my idling problems the coolant temp sensor!

[Phill 67]

Thanks very much I appreciate it. Where did you source your sensor? Did you replace it yourself? Would you have a part number?

phill

[ambermarine]

Look on eBay for LS400 coolant sensor it is green and fits just to the right hand side of the engine(lookiing from the rear of the engine) at the front top, there are tutorials on utube.

[shanra]

I would get an original part from Lexus as it is a critical sensor. Quite easy to do it yourself.

[shanra]

Trying to access the how to tutorials I keep getting an error: [[Template tutorials/front/browse/rows is throwing an error. This theme may be out of date. Run the support tool in the AdminCP to restore the default theme.]]

[steve2006]

The problem with the “How to” guides is being investigated by admin so should hopefully be sorted soon.

Part number for the sensor is 89422-30030, these are on “special offer” at LPD albeit priced at £70.00.

[MichalR]

Hi all,

nice to meet you all. I wanted to share my possible issue with 89422-30030.

Symptoms:

- car starts perfectly and runs like it should except

- temperature gauge goes up from the moment I start the engine and reaches "red" in about 5-10min.

- even on red the fans do not start (I haven't tested them from electric point of view but fuses are OK)

- I can touch the thick rubber hose that goes to the radiator and it is hot but I would say about 50 deg Celsius so not very high

- I removed the temp sensor and measured resistance, it was about 500 Ohm when hot (but cool enough so I do not burn myself) and about 1k Ohm when it cooled down a bit when I removed it. I cannot find any specs for this sensor.

 

Any idea what it could be?

Also I found the sensors to be  here in quite reasonable prices - should  I just change it or there is some spec I should use to test it?

[Mikaelse]

Sounds like the sensor you removed is working.  I have never had any sensor problem with my LEXUS cars. However on a VAG car it took me a long time to understand that they actually use 2 separate sensors and one was giving me intermittent problems. Changing the OK one obviously did not help. 
Eventually I exchanged the failed one for a non oem sensor (inexpensive one) and it worked but was so so within spec and stopped working after about 2 years . Buying OEM or a well trusted brand at least is a good idea. I often buy brands I trust.  brembo brake stuff , NGK, Nippodenso, Some Bosch stuff , SKF.  Mostly much better prices compared to OEM. Most Suspension bushings I have bought OEM .