Weird Idle

[Al.]

Hi Everyone,

I have been a lurker on this website for many years, I own a 98 LS400 (second owner) for the last 5 years.

I have never had any issues with the vehicle whatsoever. Currently I have 91K miles on the ODO (it is due for a timing belt replacement, will be done in the next 2-3 weeks).

Recently I noticed that the car idles around 650 RPM in park or neutral, once I put the car in Drive the idle will drop to 300 RPM and will maintain that RPM even in a bumper to bumper traffic, at a stop sign or set of lights, the car never stalls at that RPM level and I never experienced this before and of course no engine lights that can lead me to the cause. (historically the car always idled @ 650 RPM in neutral or in Drive).

I took the car to a local mechanic (always services my vehicles) and was not able to trouble shoot the problem and also was able to confirm that it is not IAC or the Air Mass sensor. Also he checked the Air Intake and stated that is so clean that you can eat off of it.

Note: The car received a new set of spark plugs 11K miles ago as preventative maintenance as they were not in need of change at the time but I did any how.

I have done a search and I am very much aware of the ECU problems that plagued the 94-96 Models. I am not sure if the 98-00 has a similar issue, I have checked all data for TBS on this and nothing was published.

Thanks to all I look forward to your advise and direction.

Al.

[oohryry]

Hi Everyone,

I have been a lurker on this website for many years, I own a 98 LS400 (second owner) for the last 5 years.

I have never had any issues with the vehicle whatsoever. Currently I have 91K miles on the ODO (it is due for a timing belt replacement, will be done in the next 2-3 weeks).

Recently I noticed that the car idles around 650 RPM in park or neutral, once I put the car in Drive the idle will drop to 300 RPM and will maintain that RPM even in a bumper to bumper traffic, at a stop sign or set of lights, the car never stalls at that RPM level and I never experienced this before and of course no engine lights that can lead me to the cause. (historically the car always idled @ 650 RPM in neutral or in Drive).

I took the car to a local mechanic (always services my vehicles) and was not able to trouble shoot the problem and also was able to confirm that it is not IAC or the Air Mass sensor. Also he checked the Air Intake and stated that is so clean that you can eat off of it.

Note: The car received a new set of spark plugs 11K miles ago as preventative maintenance as they were not in need of change at the time but I did any how.

I have done a search and I am very much aware of the ECU problems that plagued the 94-96 Models. I am not sure if the 98-00 has a similar issue, I have checked all data for TBS on this and nothing was published.

Thanks to all I look forward to your advise and direction.

Al.

Sounds like you are about to have the same problem that I have. Throttle Body. That's what happened when I first had trouble with my throttle. However, Lexus told me it needs to be replaced. I'm aint got 1300 to give when health insurance is 600.00 a month. I ride around with the A/C on. But hey, they have a throttle body cleaning post on here that shows you how to clean it. Just my opinion, hope that helps. But you gotta still love it considering you never had any problems out of her. Only other vehicle I can say that for was my Camry.

[Al.]

Hi Everyone,

I have been a lurker on this website for many years, I own a 98 LS400 (second owner) for the last 5 years.

I have never had any issues with the vehicle whatsoever. Currently I have 91K miles on the ODO (it is due for a timing belt replacement, will be done in the next 2-3 weeks).

Recently I noticed that the car idles around 650 RPM in park or neutral, once I put the car in Drive the idle will drop to 300 RPM and will maintain that RPM even in a bumper to bumper traffic, at a stop sign or set of lights, the car never stalls at that RPM level and I never experienced this before and of course no engine lights that can lead me to the cause. (historically the car always idled @ 650 RPM in neutral or in Drive).

I took the car to a local mechanic (always services my vehicles) and was not able to trouble shoot the problem and also was able to confirm that it is not IAC or the Air Mass sensor. Also he checked the Air Intake and stated that is so clean that you can eat off of it.

Note: The car received a new set of spark plugs 11K miles ago as preventative maintenance as they were not in need of change at the time but I did any how.

I have done a search and I am very much aware of the ECU problems that plagued the 94-96 Models. I am not sure if the 98-00 has a similar issue, I have checked all data for TBS on this and nothing was published.

Thanks to all I look forward to your advise and direction.

Al.

Sounds like you are about to have the same problem that I have. Throttle Body. That's what happened when I first had trouble with my throttle. However, Lexus told me it needs to be replaced. I'm aint got 1300 to give when health insurance is 600.00 a month. I ride around with the A/C on. But hey, they have a throttle body cleaning post on here that shows you how to clean it. Just my opinion, hope that helps. But you gotta still love it considering you never had any problems out of her. Only other vehicle I can say that for was my Camry.

Thanks 00hryry......I very much appreciate your response.

The funny thing is when I drive the car at night and of course the lights are ON the RPM is around 550 vs 300 when @ a stop sign.....I noticed this as I was driving home today.

Also I am being told by a friend that Lexus had a Bulletin for a revised Throttle Body for 98-00 models that even impacted the GS 400 & GS 430.....I called the dealer on this and the Service Advisor said based on my VIN # there was nothing available.

I am very much tempting to call Lexus and verify his response on this. The throttle body is very much clean according to my mechanic but it will not hurt to have him do it again since he did it as favor the first time.

By the way when you cleaned your Throttle Body did that work for you ? I mean did the RPM ever went back to the 600 RPM range or not ?

I also know that the tutorial on this web site is geared towards 91-97 but not 98-00 (different engine design as you might know).

Apologies for being long winded here but I am trying to get down to the trouble area if possible so I can fix it and move on, but not through Lexus as $1,300 for the job is ridiculous.

Thanks again.

Al

[SKperformance]

Try sea foaming the engine first and then do an oil change it may be as simple as old oil and carbon build up.

[Al.]

Thanks SKperformance for the tip - I will be doing so either later today or tomorrow and I hope that will take care of it.

If I am not mistaken the steps are very simple:

1- Make sure that the engine has been warmed up then turn it off and add 1/2 a bottle of seafoam (6 Ounces) then re-start the engine and let it idle for 15 minutes.

2- Turn off the engine and let sit for an hour.

3- Drain the oil and then flush with 2 quarts of oil.

4- Replace the old filter with a new one and fill the engine with fresh oil and that should do it.

Also do you recommend doing the Throttle Body with Seafoam, if so can I use the hose that goes to the brake booster to feed the left of the seafoam through ? or do you recommend other hoses to do the job through.

I heard that this may foul up the spark plugs ??? (not sure on this one) but also will not hydro lock the engine, once the engine had taken all the 6 ounces of seafoam turn off the engine and let it stand for 15 minutes and then re-start and do some spirited type driving from there.

I hope I am correct in my details above....please feel free to add any comments to correct me or that can help me complete this procedure properly.

Thanks in advance and I appreciate all of your feed back.

Al

[lexusnutt]

Thanks SKperformance for the tip - I will be doing so either later today or tomorrow and I hope that will take care of it.

If I am not mistaken the steps are very simple:

1- Make sure that the engine has been warmed up then turn it off and add 1/2 a bottle of seafoam (6 Ounces) then re-start the engine and let it idle for 15 minutes.

2- Turn off the engine and let sit for an hour.

3- Drain the oil and then flush with 2 quarts of oil.

4- Replace the old filter with a new one and fill the engine with fresh oil and that should do it.

Also do you recommend doing the Throttle Body with Seafoam, if so can I use the hose that goes to the brake booster to feed the left of the seafoam through ? or do you recommend other hoses to do the job through.

I heard that this may foul up the spark plugs ??? (not sure on this one) but also will not hydro lock the engine, once the engine had taken all the 6 ounces of seafoam turn off the engine and let it stand for 15 minutes and then re-start and do some spirited type driving from there.

I hope I am correct in my details above....please feel free to add any comments to correct me or that can help me complete this procedure properly.

Thanks in advance and I appreciate all of your feed back.

Al

Al, I had the same exact problem with my '00 as you are experiencing. Drove me crazy!

I did the seafoam in the oil and booster and the problem seems improved with the idle dropping maybe 10% of the time. Maybe I'll do another treatment and it'll get the other 10%!

I checked my plugs after the treatment and although they seemed to be fine, I replaced them anyway (50k). I think the thin wire iridium plugs are less inclined to foul.

On another note, to avoid hydrolock, do not let the car get too warm prior to feeding seafoam through the booster...

Good luck!

[Al.]

Thanks lexusnut for the sincere advise....I will be doing the seafoam tomorrow in the T.B. and the Engine and I will update the board with the outcome.

Thanks to all who responded.

Al.

[Al.]

Well.....I did the seafoam thru the engine and the brake booster, the only change I got is the idle in gear (D) went up to 400 RPM, and after a 50 mile ride it went back again to 300 RPM.

I believe 2 additional seafom treatmeants will get this issue resolved. The amount of smoke was unbelievable...and that's why I am considering additional seafoam treatments in the next 3-4 days.

Then after I solve the issue I will go after my mechanic who told me that the Throttle Body was so clean that you can eat off of it.

Thanks

Al.

[SKperformance]

The idle problem will need to have the throttle body cleaned to reap the most rewards as unless you use the intake to ingest the fluid it cannot clean where it cannot touch which is the throttle body.

[92Lex]

Actually, get your engine as hot as you can because the chances of an engine hydro-locking is more likely when cooler.

[Al.]

SKperformance - I see your point and thanks for that.....so which vacuum lines will lead to the T.B. ?

If not then I will have to take Air Intake housing off and have the car running then spray directly on the throttle Plate (the dirty side) and beyond that of course......am I correct in my assumption here ?

92Lex - There seems to be 2 different train of thoughts regarding as to when you feed the Seafoam through the Brake booster line.....Warm engine or HOT engine ? I did it with a warm engine and I did not experience anything except lots of smoke.

Thanks Al.

[92Lex]

Get the engine to normal operating temperature. This can be achieved on a cold engine by holding the RPM's steady for 3-5 minutes @ 2500-3000 RPM's.

[Al.]

Thanks 92Lex - I have located another Vacuum Hose that feeds directly above the throttle plate.....so I fed the engine additional 6 ounces of seafoam through it yesterday and the RPM has gone to 400 RPM when the car is in drive....this is a bit better than before and of course I will continue to do this periodically over the next month or two and hopefully I will reach the desired results.

Thanks

Al.

[SKperformance]

Actually , using seafoam you do not want to get it to normal operating temp as sea foams boiling temp is low and will evaporate before it will work. You just need to have the car run for 2 minutes at idle from cold start. Then use seafoam by pouring it in the intake hose as all the vacuum hoses are after the throttle plate. I drilled a hole in my intake and use it for using seafoam at each oil change twice a year.

[Threadcutter]

Actually , using seafoam you do not want to get it to normal operating temp as sea foams boiling temp is low and will evaporate before it will work. You just need to have the car run for 2 minutes at idle from cold start. Then use seafoam by pouring it in the intake hose as all the vacuum hoses are after the throttle plate. I drilled a hole in my intake and use it for using seafoam at each oil change twice a year.

S:

I understand and agree with what you've said.

Where d'ja drill the hole? (Specifically?)......pix would be nice (I know it's not terribly complicated, but at least we'd have an example of something that works right.) I don't want to experiment. If you were fortunate enough to find the "lucky spot" on accident, your success could spare the rest of us a lot of grief.

Thanks, :D

[SKperformance]

Mine just has a plastic intake so any hole made in between the throttle body and the air filter is fine.

[Threadcutter]

Mine just has a plastic intake so any hole made in between the throttle body and the air filter is fine.

S:

Approximately how big & what did you use to plug it when there "ain't SeaFoam goin' through it"?............

[SKperformance]

I used black duct tape and a zip tie before i got a small copper nipple attachment from a tranny filter to open and close.

[Threadcutter]

I used black duct tape and a zip tie before i got a small copper nipple attachment from a tranny filter to open and close.

S:

Ahhhh, so you went "the high tech/high dollar route"?....................gotcha!

Have you found that with adding SeaFoam into the intake that it has cleaned the carbon off of the butterfly plate? (I've always had to scrub/scrape it off by hand to some degree or another)

Thanks very much

[SKperformance]

It cleans it easy enough off the throttle plate. I only checked once and never looked back.

[Al.]

SKperformance - This is great idea.....I will be doing the same.....the seafoam definitely will go directly into the T.P and clean the T.B. as well.....I appreciate the great tip

Thanks

Al

[SKperformance]

no problem ,enjoy ,i know you will.

I wish it was easy to get here unfortunately they do not sell it in Canada and i have to buy it by the case when i visit the States.

The worst part is i am on my last can :(

If anyone is making a trip to my end and can grab be some i would love it thanks. You don;t know what you have until it is gone . It works for both getting sea foam and when you use it to realize how much power and mileage you lost as well as how smooth the car is.

[blake918]

Recently I noticed that the car idles around 650 RPM in park or neutral, once I put the car in Drive the idle will drop to 300 RPM and will maintain that RPM even in a bumper to bumper traffic, at a stop sign or set of lights, the car never stalls at that RPM level and I never experienced this before and of course no engine lights that can lead me to the cause. (historically the car always idled @ 650 RPM in neutral or in Drive).

My '95 does the same thing. However, living in Louisiana makes it easy to run the a/c 11.5 months out of the year, so this hasn't been too important to me. LOL I have a feeling that you are going to come up empty handed just like I did, unless the answer is numerous seafoam treatments. I'm wondering if it's something with the iacv, which I have not fooled with (it seems to be functioning fine though because my rpms jump up to 600-700 when the ac comes on.)? Removing the throttle body and cleaning it by hand did nothing for me, as did the seafoam, retuning the tps, spark plugs, etc. Good Luck and keep us posted!

Sharad, I (or maybe someone closer to the border?) would be glad to go and pickup a case of seafoam and ship it to if you find yourself in desperate need of it. ;)

[Al.]

I spoke with an old friend over the weekend, he has a 99 LS 400 with >100K miles on the ODO.

He had a similar thing happen to his car a while back, the only solution that was able to get his RPM back to normal was changing the fuel filter, it was clogged to a degree that prevented the flow of fuel under load hence the low idle in gear.

So I will be getting this one done next week and will continue with the Seafoam treatment periodically, I am sure I will get it resolved soon, so far 400 RPM while in D is a lot better than what it used to be after 2 treatments

[SKperformance]

A low idle in gear or out would not be caused by a fuel filter being clogged . Otherwise it would be worse in gear and then trying to move would be impossible to do as the fuel would dry up to the engine. It could be a partially blocked issue combined with something else to cause a low idle.