Lexus082

Not sure why, but after I had a new starter installed I had a high idle speed of around 1000 rpms. Also, when the engine is cold and is first started and the engine begins to warm up the rpm's do not drop like they are supposed to. I turn on the a/c before I put it in drive to lower the rpms so its not so much of a shock to the transmission. Which is another thing, when I turn on the a/c the idle drops, when I turn on then rear defroster the idle drops a little bit more, as with the headlights...etc... Turning on each one drops the idle speed (in park) down just a bit lower. Idle speed is steady and doesn't junp back and forth. Rpm's seem to increase slightly as the engine warms up from cold. I don't have any check engine lights on at all also.

JspecSC3

iTrader: (4)

Moved..

Welcome to ClubLexus.

FormosaSC

i have the same problem, wonder if its the spark plug

Gunnar

Idle air control valve perhaps?

Lexus082

Wouldn't that cause an low and high unsteady idle (back and forth) or throw a check engine light? I understand how it could be the IACV from researching what it actually does. Most people have stated along with the faulty IACV their idle speed changes from low to high, back and forth. Maybe that symptom is not true in all cases. I'm just trying to logically troubleshoot it, but I'm not too familiar with the iacv.

Gunnar

Yeah, when I think bad IACV I think of a car having idle surge, I've honestly never heard of a car having your problem.

Lexus082

What if the iacv failed completely, would you get a constant idle speed if that valve couldn't open or close at all.

Carib

I had a similar issue caused by multiple problems.

When I changed my starter, I forgot to connect the plug for the Idle Control Valve... when I started the car, it raced up to 3000+ rpms. After connecting it the revs settled at a 1500 rpm, which was better, but not good enough.
After more troubleshooting, I found one of the air hoses was not tightened properly... (this is the big one that connects to the IAC valve).

The revs dropped, but only to 1200rpm or so.
Turned out it was cracked... Replaced it, and now the engine idles at around 600 rpm when warm and about 1000rpm when cold (it progressively drops as the engine gets warmer).

With that said, double check the air/vaccuum hoses...
Hope this helps with your troubleshooting...

Lexus082

When you had this problem did the crack in the hose prohibit the engine idle to progressively drop as the engine warmed up? My idle speed doesn't come down as the engine warms up from cold. In fact it increases slightly.

Lexus082

I took the car to the Lexus dealer and they told me I needed a new throttle body assy. I took the throttle body off the car completely and cleaned it. Then I checked the butterfly valve to make sure it closed all the way and that it wasn't stuck. Everything seemed like it was ok with it. Is there anything else that could be possibly wrong with the throttle body that would require a replacement?

I ordered a used throttle body and am still awaiting its delivery on Monday. I still have a feeling thats not causing the high idle, but won't know for sure until Monday.

Also, one other thing to note: when Toyota replaced my starter whenever they re-installed the throttle body the dash-pot filter and cap were missing. For those that don't know, Dash Pot (DP) System is to improve driveablility, when decelerating the dash pot opens the throttle valve slightly more than at idle. This causes the air-fuel mixture to burn completely. Does anyone think that since that filter and cap are missing that maybe contributing to the higher idle speed? Everything was ok, before I took the car to toyota to have the starter changed. They also told me the TPS sensor was going bad. So when I got into my car for the first time since the starter was installed it started, but had a very low idle speed and the car was shaking a little bit. So I told the service advisor that and he said once the TPS sensor is changed out it would probably stop the low idle/shaking. Since I had the TPS sensor replaced its had a high idle speed.

Blizzy

iTrader: (-1)

when you said that you investigated the throttle body and the butterfly was working perfectly, my initial reaction was the TPS. If the throttle is working, but the TPS is reading its location wrongly, choppy idle is a potential result.

Given that the TPS has already been swapped out, I would definitely check your hoses and inquire about that DP System with the dealer. I have no experience with this DP system, but perhaps that is indeed an issue if the installation of that was linked to the idle problems.

Lexus082

Well, today I swapped out throttle bodies. The idle speed is now too low and it idles at 400-500 rpms. The entire car shakes slightly, (hopefully just due too the low idle speed. So now its doing basically the same thing as when I first got it back from the toyota dealer; low idle speed and car was shaking slightly. For some reason, I'm afraid after driving it a few hundred miles the computer will try to adjust and may cause it raise the idle speed back up to a 1000 rpms. I installed the used throttle body that included the tps sensors. When I accelerated ever so slightly in park to bring up the rpms the car stopped shaking, but when I take my foot off the gas the rpms go back down to 400-500 rpms it starts to shake again.