USMC97LS

Hi everyone. Bought a 1997 LS400 with 95K miles a few months ago. Recently, it developed a high idle and CEL came on with P0505 code. Dealer "confirmed" it was the Idle Air Control Valve (IACV) and wanted over $1000 to replace it. Bought a used one of eBay and swapped it out. Now the idle bounces between 1-2K RPM. Now some of the things I've done so far:

Before IACV swap:
- Replaced fuel filter
- Seafoam treatment
- Cleaned Throttle body
- Tried to adjust TPS to lower idle

After IACV swap:
- Reset ECU
- Checked for vacuum leaks
- Replaced ECT sensor
- Sprayed "wire dryer" on ignition components / dried with air

Significant Note: About a cup of coolant spilled out of one of the lower hoses of the IACV while removing the original. I figured problem was being caused by wet electrical components but after spending over an hour drying every wire and connector; now I'm not so sure.

Also, car did pull a P1305 code but after checking the connections on the No.2 Ignition coil, light/code went away.

Any suggestions will be GREATLY appreciated. This car is starting to get the best me!

python

iTrader: (4)

no code now? maybe the ecm is relearning. just a thought

USMC97LS

Hi Python,

I've started the car about 30 times so far and had it on for a total of about 10 minutes. How long does it usually take for the ECM to relearn?

Here is a video I just took to give you guys a better idea of the problem:

Thanks.

SC400slide

iTrader: (11)

The CEL is on I see, you should check that out, even it if went away. LScowboyLS would know maybe...

USMC97LS

Just went out to confirm, CEL is NOT on anymore. If/when if comes back on, I'll see if there is shows a new code. Good catch.

python

iTrader: (4)

it will take awhile..go drive it for about 30 minutes to an hour

jhdezls400

Turn ON the car pinch the hose the one came from the intake air connector an you will see the change on the rpm's just pressing this hose the one that go to the IAC Valve the if you see the difference the IAC is bad if you are lucky you cut find one at the junkyard

jhdezls400

I hope this helps!..

LScowboyLS

I had the exact same idle bounce on my 1996 - it turns out it was a combination of bad IACV, and bad ECU caps.

you need to go through the test procedure in the factory service manual to verify if the IACV problem is bad coils or bad bearings inside it, mine was bad bearings - I invented a poor man's IACV out of the cover of a child's notebook for a cost of like $1 and it solved the bouncing idle!

here is the test procedure from the Lexus factory manual - if test 1 fails, you have bad IACV coil, if test 2 fails, you have bad bearings (which can be replaced for around $50 and a helpful machine shop)

USMC97LS

LScowboyLS,

I just got the equipment to test the IACV and just tested the original one I pulled off. It passed the resistance test but did not open/close when tested with the battery.

Unfortunately I did not test the IACV I bought off eBay before I installed it. I will pull it off and test it tomorrow and post the results here.

If it ends up testing OK then my next move is to check for the leaking capacitors.

PureDrifter

iTrader: (10)

+1 sounds like you replaced your IAC valve with another dead one, provided everything was plugged in and connected as it's supposed to have been and there arent any vacuum leaks.

LScowboyLS

if either of them don't open/close with the battery applied, and they past the resistance test, it means that one or both bearings have seized

You can get the new Japanese bearings, but they are not down at the corner auto parts store, I had to go to a bearing specialty place and even they had to order them, total cost was around $50 for the 2 bearings together, one was significantly more than the other, as I recall, and I stuck with very high end Japanese brands, like the ones that came in it.

You will either need a press or have them professionally pressed in, any good machine shop can do it in 5 minutes for $10

while you are waiting for the bearings to arrive, you can always make my poor man's IACV , I drove with it for a year, it's great, almost as good as the real thing, especially if you aren't in International Falls, MN or somewhere.


Oh - I almost forgot! - if you are going to replace the bearings and rebuild one like new, you need to get yet another one on ebay, (non-working is fine if the coils are good) and this time you want the one from the 90-94 models, the reason is, it is essentially identical except like one of the hose sizes requires a slight adaptation, but the important thing is, the 90-94 IACV can be opened up with tools, the 95-97 cannot, but the 90-94 works fine on our 95-97 models. - it would require cutting open to use our year's model, and that is just a lot of needless work, not to mention you have to find a way to reseal it.

Our ECU's don't care that it is the prior generation, the IACV is really a pretty dumb device when it gets right down to it!

USMC97LS

UPDATE: Tested the "new" IACV that I got off eBay and .... passed resistance test but does NOT open or close. You called it PureDrifter. I even bought the one that was advertised as "cleaned and tested" and paid more for it!

Off to eBay for a 90-94 IACV so I have the option to rebuild later on down the road. Might even call around to a few local junkyards to see if they have any older LS(s) to pull from. Thanks LScowboyLS.

LScowboyLS

to use the 90-94, you will have to adapt a vacuum line or two, as I recall, at least one of the lines is like one size off, so you need one of those vacuum line step up or step down adapters, it is one of those that goes over to the snorkel

python

iTrader: (4)

https://www.clublexus.com/forums/sho...d.php?t=551125