///MDex

But ther is no either when the car is in drive and your foot is on the brake, right?

BananaGS

Engine is loaded when you are in D, whether you are on brake or not, the TC still spin, but due to the fluild transfer, the car can control some of the hydraulic valves in the tranmission to diverse the fluid power so your engine won't die. (ie ever drive a clutch equipted car? hee hee, if you don't engage the clutch in 1st and you are on brake, you know what happen when the moving engine is directly connect to the non-moving wheel hee hee)


As far is this problem goes, I had the following replaced:
-TPS sensor
-TPS assembly
-Throttle body (includes all the motors and electronics on the throttle body)
- can someone here replace the MAF sensor and let me know?

-Still have low idle at stop light. (400 rpm), I managed to increase the throttle cable tension just a tiny bit, got the idle rpm up to 620rpm now. I think I will back it off to 500 or so. So far, this is the only fix that work for me consistently (2 week of running, the car drop down to 400 only ONE time, instead of 80% the time, so I am pretty happy with this)
(yes I know the car throttle is electronic controlled )
-Side effect of this adjustment is: the car take ever to slow down when you let your foot off the gas, so this is not a great fix..

BTW: no complaint about my car or Lexus service
I would buy Lexus again any day.

JacobT

I think it's the ECU software programming issue. In order to achieve the Ultra Low Emission goal. Toyota designed the fuel mapping idle way too low. They probably designed it with some accessaries turned on but induced a bug in there when there's nothing on except the engine load.

How about a new ECU to fix the problem

Hohlraum

1. yes I have the low idle problem
2. it only happens with the heat/AC off (and I wanna say its only when i'm in POWER mode, but I don't recall)
3. its never died on me and if ever did I'd be seriously pissed

I had a 300M with a rough idle problem (can't remember if it ever died though) after a couple years of ownin it.. they replaced some TXX (where XX is two letters i cant remember hehe) valve and it fixed the problem. Might be common among a variety of cars.

GSquicksilver

as far as i know, i believe only the GS430 achieved the ULEV status, not the GS400. for sure, i know the GS400 didn't qualify for a LEV, but i believe the 99 model did. can someone verify this?

ChrisK

iTrader: (1)

My 95 SC400 has similar problem as well. On hot days, when driving with A/C on the car idles OK at 800 rpm. On the other hand, when I decide to shot the AC off, while driving, when I get to the stop the car idle drops to 200 rpms and sometimes dies. Also I've noticed that the car takes its time to readjust when A/C goes off or on. For example, when sitting at the light I turn the A/C on the rpms will jump from 400 to 1000 and after the second it will go down to 800. As much as the rpms should jump up with additional A/C load, I don't believe it should go to 1000 and drop down to 800. The same problem is with turning the A/C off. First it drops very low, 200 rpms, and goes back up to 400 rpms after a second. Same scenario happens when while in motion the A/C is getting turned off, when coming to the stop the idle is "getting lost" at first and then it "finds" itself. I personally think this is the computer programming problem. It simply cannot adjust quickly enough to new conditions, and it doesn't recalculate on the fly, it waits for things to happened first and then it is trying to readjust.

GS4spinnin

I just bought some new plugs from the dealership, Denso Iridiums, and my low idle problem went away, it would die on me and shake my car also at red lights, but the new plugs fixed the problem for now anyway, try it out if you guys want...

CKIM

iTrader: (1)

I have a CPO '99 GS4 (bone stock) that was idling around 500 at a stop. I took it into the dealership, and they came to the conclusion that it was due to carbon buildup in the throttle body. After getting raped for $100 for the work that probably took 10 minutes, I took it back 3 days later because my car was idling between 400-500 at a stop. So whatever they did made it worse. These guys at Jim Falk lexus have no idea whats wrong. So like you Bananags they are replacing my throttle body again. This will be the 2nd time I'm getting my throttle body replaced, because the first one failed a year ago.

I'm really getting fed up with all this. If anyone is taking this to corporate add me in.

Chris

GSquicksilver

GS4spinnin,

the first thing i did was replace the spark plugs with brand spankin new denso iridium plugs. same issue. i still say we should SUE lexus for this BS

Threxx

Every automatic vehicle I've ever seen has had a very different idle RPM from neutral\park as compared to drive or reverse.

The load is completely different from one to the other. In neutral the engine is seperate from the transmission, in drive it is engaged with the transmission, even if you aren't actually moving... the hydraulic pressure is there.

UTGS400

So far my dealership has tried cleaning the throttle body and increasing the opeing of the throttle body from 12% to 15%. Now the problem is even worse. When I start my car, the tachometer bounces from 300-600 rpm and finally comes to rest around 500 RPM. Every few stops, the RPM's drop to around 300 and eventually come up to around 500 RPM.

The mechanic stated that he has had many complaints about this problem and has started investigating. Next on my list is the replacement of my throttle body.

JacobT

Chad,

Have you talked to Randy who is the chief tech. in Lex of Austin. He replaced my TPS and now the car idles at 625 prm constantly.

UTGS400

Yes, Randy is the guy who has been helping me out. He seems like a great guy...I have faith he will solve my problem.

twenty1

add me to the list of those that have read this thread and now feel better knowing that they aren't the only ones having problems with their idling. i will re-post what i wrote in another thread, and give you part 2:

i don't know if i'm posting this problem in the right spot. if i'm not, please forgive me. anyway, the check engine light of my 98 gs4 came on saturday afternoon, and was on all day late saturday afternoon until mid afternoon sunday. i had turned the car off, and when i came out later and turned it on, it was gone. it was about 75-80 degrees then. our first genuinely warm day in mn so far. today, it was 90. late afternoon
today check engine light came on. as i left target and was pulling out the parking lot, the car cut out. i started it back up again, and i pulled into a parking lot, and noticed that it was running at really low idle rpm 250-500. it was on the verge of cutting out again, but i turned the car off. i was on the phone with lexus service at the time. upon restarting, i was having the same idle problem, but the car didn't cut out for the remainder of my drive home (about 1.5 miles). i guess i'm kinda inferring that maybe this is heat related. maybe it's just a coincidence.

part2:
now i know it's not a coincidence. i got my car back thursday. it ran fine, but i hadn't paid attention to where it ran when it was idling this morning, it hesitated for a second during acceleration. it cooperated fine the rest of my drive to work. i left work to go to mcdonalds and i was losing power (acceleration), and then it would come back, like i was running out of gas. i made it thru the drive thru, and a block away from mcdonalds, it died at a red light. every time i tried to re-start it, it would turn over, and rpm's would be low, and it would cut out. it all happened fast enough that i basically had to sit in the intersection, stuck. roadside assistance got called, and they came and towed my car. second time i've had this problem in a month. i had no problems prior to this. this is beyond unacceptable to me. and the most frustrating part is, it doesn't sound like there's a solid solution!!!

so, i will keep everyone here posted on what happens with mine. they replaced the fuel pump the first time. they couldn't find a problem at all, but they did it in hopes that if there was a problem that they couldn't find, that would fix it. what i want to know is, is anyone here writing a letter? if noone responds that they have by monday, then i will. matter of fact, i'm gonna write one in the meantime. if this problem continues, more than letter writing may have to happen to get the problem rectified. but, it's a start...

twenty1

well, sounds like i had a different type of problem. my fuel gauge indicator is way off. i had a little less than half a tank showing, when really, it was on E so, they are going to get that fixed, and give me a full tank of gas. hopefully, that is all the problem that this is, and nothing else. will keep you posted...