Idle Rpm

[Csosz74]

Hey guys,

there's a question I've always wanted to know the answer for.

I have a 1990 Ls400. When I start the car and the engine is cold, my RPM is (with the trans at D) around 400-500 rpm. I leave for work and go cca. 18 miles on the freeway. When I exit the freeway and stop at the red light, then the rpm goes down to 200 (in D of course). Is this normal? Of course I know that when it's cold then the rpm is higher, I just don't know how it's called in English. Why it doesn't lower the rpm while driving? It only does when I stop for at least 15 seconds.

Hope I was clear

A

[steve2006]

Hi,

Search the forum for throttle body cleaning and ICV cleaning your RPM should be 650 when the engine is warm.

[eatingupblacktop]

Idle should be ~650 rpm.

[Csosz74]

thanks

will do that

A

[oldskewel]

Hey guys,

there's a question I've always wanted to know the answer for.

I have a 1990 Ls400. When I start the car and the engine is cold, my RPM is (with the trans at D) around 400-500 rpm. I leave for work and go cca. 18 miles on the freeway. When I exit the freeway and stop at the red light, then the rpm goes down to 200 (in D of course). Is this normal? Of course I know that when it's cold then the rpm is higher, I just don't know how it's called in English. Why it doesn't lower the rpm while driving? It only does when I stop for at least 15 seconds.

Hope I was clear

A

Those numbers sound pretty low. My '91 idles smoothly at 600 when warm, maybe 1000-1200 when cold. AC on/off will affect this as well. It seems almost impossible that your car could really be idling at 200 - seems it would be very rough and stall.

Does it seem smooth at 200? Assuming it does, my first guess would be that your Tach needle is off by about 400. So it's really idling at 600, but indicating 200. Do you have an easy way to test this separately (e.g., timing tool around an ignition wire)?

Here's another way - I've noticed that redline for my '91 is spec'ed at 6000, but in a WOT startup, it will shift at 6200. If you do this test (professional driver on a closed course private road with helmet on, of course) and you notice it shift to 2nd at 5800, it would be another indicator of the needle being off.

[jcrome04]

In D I'm at about 600, sometimes a little lower.

I still need to clean my IACV :P

[VBdenny]

engine should idle exactly at 600RPM's when engine is up temperature.

[Csosz74]

engine should idle exactly at 600RPM's when engine is up temperature.

Is that in 'D' or in 'P'?

Here are my numbers:

cold start in 'P' 1000rpm, in 'D' it's 600. When it's warm, 200 in 'D', and it runs smooth. When I add gas to rev up to 600, it does not sound really well.

I can live like this, the only thing that bothers me that I leave from work, take the freeway, after 22 miles I arrive to home and it still on higher rpm, only when I stop at the parking lot then it calms down, not on the way home during driving.

That means it consumes more fuel I guess.

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