Idle Issue With 93 Ls With 150k

[DuaneG]

I just spent the better part of 2 hours reading an older thread on here concerning an idling issue with 95's and I read that there were some older LS's with similar problems:

1. Car will idle in 500-600 range, then drop to 300-400, then go back up to normal.

2. Occasionally it will- when stopping- drop below 200RPM for a second, then back up to the normal range.

3. There have been times when the car has died on pulling away from the light. This has happened a couple of times.

4. This problem has only happened to me when I am stopped at a light or when the car has been running for a very short time after sitting for a few hours to overnight.

5. The problem is intermittent, although I feel the problem will get more frequent if not addressed.

I read a couple of possible fixes:

1. Fuel filter

2. IAC?? Where is it?

3. ECU, but that has not been verified for older than '95 cars.

I have this problem and I am searching to fix it, so I thought I would start this thread so that we can find a solution for the old LS's

D

[vyhanh]

Do a search for trunk wiring.

Good luck

I just spent the better part of 2 hours reading an older thread on here concerning an idling issue with 95's and I read that there were some older LS's with similar problems:

1. Car will idle in 500-600 range, then drop to 300-400, then go back up to normal.

2. Occasionally it will- when stopping- drop below 200RPM for a second, then back up to the normal range.

3. There have been times when the car has died on pulling away from the light. This has happened a couple of times.

4. This problem has only happened to me when I am stopped at a light or when the car has been running for a very short time after sitting for a few hours to overnight.

5. The problem is intermittent, although I feel the problem will get more frequent if not addressed.

I read a couple of possible fixes:

1. Fuel filter

2. IAC?? Where is it?

3. ECU, but that has not been verified for older than '95 cars.

I have this problem and I am searching to fix it, so I thought I would start this thread so that we can find a solution for the old LS's

D

[steve2006]

1st fix normally is to clean the throttle body see link below on how to

http://www.lexls.com/tutorials/EFI/throttlebody.html

[eatingupblacktop]

Here's a link for Step By Step Instructions For Iacv(idle Air Control Valve)/isc/throttle, and Step by step instructions on cleaning the IACV/throttle body:

http://us.lexusownersclub.com/forums/index...showtopic=30723

[vyhanh]

Sorry: Your link referred to RX300 not LS400 !!!!

Here's a link for Step By Step Instructions For Iacv(idle Air Control Valve)/isc/throttle, and Step by step instructions on cleaning the IACV/throttle body:

http://us.lexusownersclub.com/forums/index...showtopic=30723

[eatingupblacktop]

Sorry: Your link referred to RX300 not LS400 !!!!

Here's a link for Step By Step Instructions For Iacv(idle Air Control Valve)/isc/throttle, and Step by step instructions on cleaning the IACV/throttle body:

http://us.lexusownersclub.com/forums/index...showtopic=30723

So you noticed? My bad. Didn't title it properly. Happens.

Nevertheless, here's a pic of what it looks like and and exploded diag to show where it's located.

It's on the TB. If you look at the diag, it's the one on the left side. I've colored it yellow.

Before replacing (they're not cheap), a couple of things you can check are the gasket and the plug. Make sure the connectors in the plug are clean and the connection is tight. Another is the spring. Make sure it's clean and working properly.

[glenmore]

I have a 1990 with similar symptoms. The idle has dropped to about 400 all the time now from IIRC about 550. A few times the car has unexpectedly rev than returned to normal, sometimes the RPMs will drop and the car will stall. Changing the fuel filter and cleaning the throttle body has had no effect. I "think" it is a dirty or failing idle air control valve (iacv). Since symptoms have been rare and the car is away from home, I haven't done anything further. A new part is around $600 from Lexus. They pop up occasionally on ebay.

glenmore

1990 LS400

1991 300Ce

2000 C280

[DuaneG]

I know. I have the same intermittent dilema. I will drive the car for 4-5 days with no problem, then it will happen once. I may try the throttle body fix and see how it works for me.

D