Very Dangerous Problem Happening....looking For Help Please

[nll714]

95 LS400 with 150k miles. I am having a major, and very dangerous problem that I hope you can help with. After driving on the highway for a long trip, and when I get off and start to slow down / come to the first stop, my car konks out! Sometimes this happens before I come to a complete stop and Im still moving but the car has shut down. Almost got in a wreck because of this today. I put it in neutral and it starts up no problem. Put it in gear and Im on my way.

This NEVER happens when Im traveling locally, just coming off a highway trip. Is this an idle air control valve issue? Any help or insight would be appreciated. Thanks.

Edited April 5, 2009 by SKperformance
better title

[billydpowell]

95 LS400 with 150k miles. I am having a major, and very dangerous problem that I hope you can help with. After driving on the highway for a long trip, and when I get off and start to slow down / come to the first stop, my car konks out! Sometimes this happens before I come to a complete stop and Im still moving but the car has shut down. Almost got in a wreck because of this today. I put it in neutral and it starts up no problem. Put it in gear and Im on my way.

This NEVER happens when Im traveling locally, just coming off a highway trip. Is this an idle air control valve issue? Any help or insight would be appreciated. Thanks.

I have no clue as to the problem, but do have a suggestion...

as you come to your exit, slow down, pull on the shoulder, let it die, crank it up and continue on safely. my 95 has never done this.@162k. bp

[Threadcutter]

95 LS400 with 150k miles. I am having a major, and very dangerous problem that I hope you can help with. After driving on the highway for a long trip, and when I get off and start to slow down / come to the first stop, my car konks out! Sometimes this happens before I come to a complete stop and Im still moving but the car has shut down. Almost got in a wreck because of this today. I put it in neutral and it starts up no problem. Put it in gear and Im on my way.

This NEVER happens when Im traveling locally, just coming off a highway trip. Is this an idle air control valve issue? Any help or insight would be appreciated. Thanks.

I have no clue as to the problem, but do have a suggestion...

as you come to your exit, slow down, pull on the shoulder, let it die, crank it up and continue on safely. my 95 has never done this.@162k. bp

Sounds like it's possibly your Idle Air Control Valve on your Power Steering Pump. It's the black plastic valve with two barb fittings and vacuum hoses attached to it that points down and toward the passenger side front wheel well.

Start the car in your driveway, press the brake pedal, put in drive and turn the steering wheel. If your RPM's drop or the engine actually dies, the IACV should be replaced. Some people just remove the hoses and plug them. When it happened to me, I replaced the valve.

[1990LS400]

A car having a "having a major, and very dangerous problem" should not be driven. Take to a professional if you can't fix it yourself before driving it again. If necessary, call a tow truck to have it taken in.

[amcdonal86]

You know the car can be restarted in neutral, right?

[EDIT]I'm an idiot. You already said you start it in neutral.

[SRK]

A search would reveal that this is a common problem with your year LS, and it's the ECU. Check with the dealer - many were replaced under warranty and under a campaign to correct the fault.

It's only dangerous because of the way you drive. It's not the car's fault.

[LS 0181158]

Yes, I hear it is common with the early ('95-'97) UCF20 LS 400. Have read multiple reports of this, and experienced it myself in my friend's '95. Also happened to me in a '93 I was driving for a while. Typically occurs after long periods of high-speed driving, when the car is slowed to a stop--so your description fits this pattern. In all cases, the car starts right up after you slide the gear selector in neutral. And for most people it only happens once in a while, so it's something they choose to live with.

This has never happened in my '98, so Lexus must have corrected the problem. One solution I have heard is to keep the A/C selected on manually, since this will usually prevent idle revs from dropping to the point where the engine cuts off. I'd bet each time this happened in your car, the air conditioning compressor wasn't running.

[amcdonal86]

It's only dangerous because of the way you drive. It's not the car's fault.

I don't understand. What is the meaning of this!?

[billydpowell]

It's only dangerous because of the way you drive. It's not the car's fault.

I don't understand. What is the meaning of this!?

It's only dangerous because of the way you drive. It's not the car's fault.

what kind of statement is this??

the car has a problem, not the driver.

It is not unsafe to drive, since it only happens after driving at high speeds, and you dont have to do that.

have a little mercy guys, he's just asking for help...... I think this is the purpose of this forum.

Those that know "speak", the rest of us, just read and learn something..

cheers, bp

[McSwine]

This has never happened in my '98, so Lexus must have corrected the problem. One solution I have heard is to keep the A/C selected on manually, since this will usually prevent idle revs from dropping to the point where the engine cuts off. I'd bet each time this happened in your car, the air conditioning compressor wasn't running.

My 2000 does this as well. The A/C suggestion works, and I've found it idles a little higher if the "recirculate" button is on.

[blake918]

A search would reveal that this is a common problem with your year LS, and it's the ECU. Check with the dealer - many were replaced under warranty and under a campaign to correct the fault.

I agree..... http://us.lexusownersclub.com/forums/index...&hl=jerking

[jcrome04]

Maybe you can still get it done for free! :D

[AzHotLS]

That would be nice.

I should consider myself lucky as mine was replaced for the same reason by the previous owner. :whistles:

[nll714]

Thank you all for the posts. I will be having the ECU looked into immediately and let you know the results of this.

[killerFatty]

95 LS400 with 150k miles. I am having a major, and very dangerous problem that I hope you can help with. After driving on the highway for a long trip, and when I get off and start to slow down / come to the first stop, my car konks out! Sometimes this happens before I come to a complete stop and Im still moving but the car has shut down. Almost got in a wreck because of this today. I put it in neutral and it starts up no problem. Put it in gear and Im on my way.

This NEVER happens when Im traveling locally, just coming off a highway trip. Is this an idle air control valve issue? Any help or insight would be appreciated. Thanks.

I have no clue as to the problem, but do have a suggestion...

as you come to your exit, slow down, pull on the shoulder, let it die, crank it up and continue on safely. my 95 has never done this.@162k. bp

Sounds like it's possibly your Idle Air Control Valve on your Power Steering Pump. It's the black plastic valve with two barb fittings and vacuum hoses attached to it that points down and toward the passenger side front wheel well.

Start the car in your driveway, press the brake pedal, put in drive and turn the steering wheel. If your RPM's drop or the engine actually dies, the IACV should be replaced. Some people just remove the hoses and plug them. When it happened to me, I replaced the valve.

I dont mean to be an A$$, but please get the vocab. right. The Idle air control valve is on the front of the engine and cost about $1000 to replace. The Idle up valve or idle control valve is located near the PS pump and is about $80-$100 for the part. I believe the latter is what your refering to. Again no offence, but having delt with this problem, I can't let somebe missenformed. Even if it's un-intentional. However I do believe that its an ecu problem not a result of this valve.

[prix]

others have posted (i think in this forum) about having the same issue. might want to try a search to see what else comes up.

several years ago, my first generation ls400 was doing the same thing. i would be driving around town and sometimes (not always, but often enough) it would die, almost always at a stop sign or a red light after i slowed down. i don't do a lot of highway driving, but yes, under the same circumstances it would stall. as you say, the car always started right back up. yes, it's dangerous, especially in heavy traffic.

after watching my own driving to see what i was doing just prior to the car stall, i finally realized it was directly related to running the air conditioner. to this day, i can still make my car 'die' by running the air, then driving around, and while slowing down, turning the air off. the car will die almost every time. the opposite of that is also true. having the air on keeps the rpms up and the car won't stall. that is what i do to this day. i like the air on anyway, because the air circulating is filtered. i guess it's not great for the gas mileage though, and it's harder on the battery (i think that's what someone told me).

also, if i start the car without using air and never use air at all during that particular trip, it also doesn't stall. i am pretty sure that is the case (but haven't tested that out in some time). when i get into trouble is when i turn the air on and off in the middle of driving. you can see the rpms drop way down when i turn off the air. sometimes it won't stall out; sometimes it drops so low that it will.

several people in lexus forums have commented that this is a known issue and that lexus is aware of it.

[Seba]

95 LS400 with 150k miles. I am having a major, and very dangerous problem that I hope you can help with. After driving on the highway for a long trip, and when I get off and start to slow down / come to the first stop, my car konks out! Sometimes this happens before I come to a complete stop and Im still moving but the car has shut down. Almost got in a wreck because of this today. I put it in neutral and it starts up no problem. Put it in gear and Im on my way.

This NEVER happens when Im traveling locally, just coming off a highway trip. Is this an idle air control valve issue? Any help or insight would be appreciated. Thanks.

I would try two things first:

Remove the air intake up to the second butterfly & clean any black deposits behind the second butterfly.

Clean both butterfly's if You have traction control.

If that doesn't help, Your idle valves need to be replaced or believe or not EFI relay could be overheating.

Another problem could be Your ECU as well.

[yoichisoma]

This is a known problem. Replace ECU with updated version. Check dealer for TSB. Also look up LS400bob 's thread on this. Must replace ECU and clean TB while you're at it. Can find junkyard ECU but must be the new version designed to replace original. Do not try to rebuild original. It will not fix the prob. Trust me this is the fix. I have a 95 LS with 148000. No problems now.

[josping]

Hello, I'm from Spain. my car has 200,000 kms "125.000 miles" and it happens exactly the same. but with a difference, just do it in days of less than 5 degrees celcius "41F "

[Banshee365]

What a coincidence this thread is. My '96 LS400 is sitting in the garage dead right now. The car developed 2 symptoms at the same time, however they have both happened before and went away after a while. The car has pretty new plugs, wires, caps, rotors, and a cleaned throttle body.

The car sometimes starts and the engine races to 2,000 rpm's and you have to tap the gas to get it down. Lately it's been starting normal and settling down to about 650 rpm at idle. I have also replaced the coolant temp sensor with, what seemed to me, an improved idle throughout the day of driving. It used to idle really high even when warm. The sensor seemed to fix that.

The car had been starting fine and idling correct. If you drive the car, not even on the highway, and come to a stop the idle goes down to about 200 rpm and sometimes dies because of it. It usually starts back up but sometimes is hard to start. The power steering has also gotten very stiff and doesn't seem to change much with an increase in RPM's. It's like driving a manual steering car. The fluid level is fine.

Right now, after experiencing those symptoms today, the car is dead in the garage and will no even start. I think it may be flooded but you can smell gas and everyone once in a while it will try and fire but just won't stay alive off of the starter.

What could be wrong with my car? It's primary transportation and need to get it fixed soon. The "jerking" has never been experienced in this particular car. I'm almost positive that the ECU is probably the first generation one. Should I look into the Idle control valve on the power steering or the IACV for the engine? Trying to figure out which one I need to replace first. I don't have money to play with replacing random parts. Thanks for the help in advance and hope this thread can help some others with this issue if I can get my resolved as well.

-Kelly

[Banshee365]

Well this morning the car started after a small amount of cranking. It idles at 200 rpm in neutral and about 300 rpm in a gear. I don't think this much of a variation from what it should be is due to the adjustment of the TPS. It seems like it has to be the IACV or ECU. What do you guy's think?

I still don't know what is up with the power steering. I'm going to try to clean the screen on the rack and check for vacuum leaks to try and get the steering feeling right again. It's still too stiff.

[VBdenny]

nveer had this problem on my 90 LS. The engine (once at temperature) idles at 600RPM's in or out of gear.

[curiousB]

Are you sure the engine is 200-300 RPM? The cars tach may be giving a false reading? That would be a very rough engine at that low of an RPM. If that truly is proper RPM reading then I would start by checking for dirty throttle body which could be causing air leakage across throttle plate. Also a sticky or gummed up IACV could also impede this. The trouble I have here is if the ECU sees the engine running this low it will control the IACV to open more to speed up the engine. Is the IACV stuck/sticky? Can you take it out, clean and lube it and give it a retry?

Vacuum leaks could also cause problems as the engine get more air but the airmass sensor doesn’t see this air consumption.

[Banshee365]

Curious, thanks for your reply. I'm going to try and clean up the IACV this evening or tomorrow morning. The tach is correct and the engine is idling super super low and it sounds like an old packerd V12 if you've heard one that idles very low. It does idle a little rough due to the low idle. I'll update as a soon as I try out the car after the IACV cleaning. I also read somewhere that it should click when the engine is turned off? Also, do I have to apply a charge to it to clean it? Thought I read that somewhere too.

[Banshee365]

Got the car all apart and cleaned the IACV. It didn't move very fast but after about 10-15 passes with a negative battery lead the valve would open and close. Installed everything back in the car after cleaning the EGR modulator as well. It started up great and idled a little high while cold as it should. RPM's at idle settled down to around 650 rpm as it should. Drove the car and it ran great. The steering is still stiff but I still need to clean the screen on the rack to try and help that. The pump may need a rebuild too. Anyway....

I shut the car down and it sat for about 5 minutes. I came back outside and cranked it up again. It started idling really low again. I drive it and the first stop I come to in my neighborhood it goes down to 100-200 rpm again before dieing. It would start right back up but would still idle at 200 rpm. I got it home and it died on me again in the driveway. I tried to start it back up and it just cranked and cranked. Finally after about 10 seconds of cranking it started to sputter and a puff of black smoke came out of the exhaust. the engine then raced way up without me touching the gas. It bounced between 2k-3k for a while without me touching a thing. Doesn't seem like a IACV could open far enough to let that much air in... It idled VERY irradically and I finally just shut it off while pulling my hair out.

Several hours later I go outside and it cranks up perfect and idles just great. What the heck could be going on. The current CEL shows a problem with the coolant temp circuit. I've recently replaced the coolant temp sensor for the ECU and the code went away for a while but came back. It returns immediatly after clearing it. It seems to me maybe the ECU is recieving or interpreting extreme hot then cold then hot then cold to make the revs bounce around all crazy like that. Does anyone have any ideas what's going on? Is my ECU bad? This is a tough one for me to diagnose...