Idle increases once driven

[smokeyo1]

Hi Guys
LS 400 UZE 91
On start up idle is slightly high and drops normally when up to temp, once I drive the car the idle increases and wont drop, If I turn the engine of for ten seconds and restart the idle drops to normally, but then if I drive again the same thing happens
Any one?

 

[Bushwhacker]

The IACV need cleaning?
http://www.youtube.com/watch?v=qzI6798Xpzk

 

[smokeyo1]

Cheers Bushwacker, I have cleaned it, but clearly not enough, I'll give it another go

 

[smokeyo1]

Ok Guys, I took the IACV out gave it a damn good thrashing, er I mean clean, put it back and hey presto its still the same, any Ideas?

 

[gloverman]

Any chance it has a check code? Either engine or Trans? I doing some testing recently when the ECU detected a transmission check code it would idle high. Turn it off and start it and it would drop down until driven. Once I reset the testing I was doing it was back to normal.

 

[smokeyo1]

I did a check test and it showed no code faults, but I will try again, cheers Gloverman

 

[smokeyo1]

Ok tried the check, no faults showing?

 

[spf_lexus]

You could also have an intermittent vacuum leak as this will cause a high idle. You could use a smoke machine and check for leaks or just cap off all sources and reevaluate. I would suspect the 2 P/S vacuum assist lines or maybe the EVAP purge valve.

 

[smokeyo1]

Cheers fella I'll try that, I have sprayed all hoses with wd40 and nothing changes, but worth another look

 

[smokeyo1]

I am now at a loss, although it will only do it once now, once the idle gets high, I turn it off, restart and let the idle settle down, once there it stays low and even, but its driving me nutts literally

 

[cthommes]

Thread resurrection-- I'm having this exact same symptom in my otherwise fantastic swap project (using a 92 SC400 Engine/ECU/Trans). Any new developments or was a cure ever found?