Ls4000101

I've owned my 91 LS for about 7 years now and really havent had any issues with her, besides the power steering leak taking out the alternator, or the draw from the system i have in her. She has always idled at this speed amd thought it was weird amd asked the guy I purchased her from if it was normal and he said it was. Well scrolling through some of the feeds I'm learning that it should idle a little higher, about 800 rpm? Is the correct idle speed 800 rpm or os 400 rpm the normal? I saw anthread that says you can relearn the idle by tumbling the ignition twice and start it on the 3rd with your foot on the brake. I've attempted that and she is not responding to it and continues to idle at 400 rpm. Which I have read that I will need to disconnect the battery, remove the throttle body and give it a through cleaning to hopefully bring her back to proper idle speed. Does all of this sound correct? She does have the check engine light on for the EGR valve but has not been a issue seemingly....any input would be much appreciated. Thanks everyone.

Ls4000101

Sitting trying to get her to "relearn" her idle . With everything off. I am hearing what sounds like a small electric motor whirling intermittently. No idea if its inside or outside the vehicle or if it is even related to this idle question I am inquiring about.

CELSI0R

Regular idle for our cars is around 650 RPM, if I recall correctly. I also own a 1991.

I would recommend checking your Idle Air Control Valve (IACV). I don't think the start cycling will do anything.

Another user has had what sounds like the same issue:
https://www.clublexus.com/forums/ls-...e-working.html

This owner had the 400 rpm idle issue.

Here is an in-depth write-up from PlanetSoarer:
http://www.planetsoarer.com/IAC/iac.htm

Here is a video about the IACV and cleaning it on a 1992 SC 400:

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For the EGR code:

Let us know what code you are getting. The 1990-1992 LS 400s have a vacuum operated EGR system. This is the same pretty much across all Toyotas, until the switch to the electronic actuator controlled systems (1993+ for LS 400).

Here's an informational video:

These jobs are also worth doing. The PCV valve is a commonly neglected part that is worth replacing. Just be careful not to let parts of it drop into the valve cover, upon removal:
http://www.lexls.com/tutorials/emission/pcv_valve.html

This is how to clean the EGR filter:
http://www.lexls.com/tutorials/emission/egrfilter.html

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Before changing anything, diagnose, diagnose, diagnose.

Hope this is helpful.

oldskewel

iTrader: (1)

If nothing else is "wrong," the first thing I'd consider is that your tach is reading low. So if you really want to dig into stuff, looking for a problem, I'd start by measuring actual RPM directly. You can do this with something that clamps onto one of the spark wires, counting the rate of pulses.

In general, the instrument panels on these early cars (my '91 has both tach and speedo malfunctioning) tend to fail after a while.

CELSI0R

Excellent point! I had the same issue with my cluster, before repairing it.

I actually did not know about these tachometers you mentioned, but here is a video for OP about them and how to use it:

I might purchase one myself for diagnostics. They're quite cheap, too.

timmy0tool

iTrader: (7)

low idle is a common thing on these cars as they age, but if the car drives fine I personally wouldn't worry about it too much.
usually when the AC turns on the idle should go up to compensate for the extra engine load.

the IAC clean up from plantesoarer is a likely candidate to why things are idling low.

EthanS

Once fully warmed up, have you noticed a difference in idle speed between having the transmission in D/R vs. P/N? Give it a try and let us know.