95/96 Ls400 Low Idle, Engine Dies And Jerking Thre

[Speedy J]

Hi guys,

Having read this topic and having mentioned earlier that I had the same problem of the dying engine, I sent my car to the Lexus dealer, with a reference to this topic.

It seemed I already have the updated computer (ECU) in my '95 LS. So that couldnt be the problem. The dealer had an other possibility and that was to check the fuel related items in the car. Excuse me for my bad english (dont know the terms/right words) but I will try to make this clear

They found out that the fuelpump, some related sensors, the fuelfilter and other parts that are in relation to pumping fuel from the fueltank to the engine and "giving" fuel "back" to the fueltank were "very filthy". So they took apart all the related parts and cleaned them. The only thing they replaced was the fuelfilter for a new one.

So, good cleaning seemed to have solved the problem. Costs? One and a half hour labour (€ 120) and a new fuelfilter (€30).

I took the LS out for the trips at which the problem always came up and guess what...no problems any more! Nice idle at around 600, not less (was getting used to 300, 150, zero...)

I hope I made this solution clear, if not, just ask. Hopefully some of you can use this solution...

PS There were indications about this problem arising at mileages above 200000 km...well, considering that parts may be poluted after so much time/miles this may sound logical now.

Greets from Holland, Speedy J

[flash213]

Im trying to recreate the engine dying so when I put my new ECU in I can test it. The time I had this happen was on the 1200 mile drive home from buying. I'd liked to hear about how long of a drive usually triggers this problem. I dont want to have to drive 1200 miles again. LOL

[95LS400Bob]

I could make mine do it at 65 miles of cruising. Shorter peiods it just would not do it. The only way I knew I got it was drive the same distance...in fact..I went to the same town right where it died before. Turned around and came back...even went 20 miles further and it was still o.k. Then I knew I had it.

Speed may be a player..keep it at least 60 mph.

[flash213]

In Ls400BOB's orginal post he refers to the TSB's. What is a TSB and while we are on abbreviations what does OEM stand for. I infer that it means originall part. Just wondering.

[95LS400Bob]

Technical Service Bulletin.

[iatimlee]

Technical Service Bulletin.

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OEM = Original Equipment Manufacturer

Once I got my ECU back from upgrading at Auto & Truck in FL I went for a short (5 mile) drive to be sure the car ran OK. The next time I drove it was a few hours later when I went to the airport to pick up my wife. The car died at the airport exit which was 32 after miles of 70MPH driving. The new ECU only had 47 miles on it and it was showing the same symptoms. It idels down to 200 or 300 almost every day on my way to work after a non stop 17 mile trip at 70MPH. It may only die once or twice a week on that leg of the daily trip.

I had always wondered if this issue was related to aging parts - otherwise it shoudl have been more visible at time of purchase and Lexus woudl have been in for a recall and/or a lot of customer dissatisfaction - a lose-lose for them and the owner. I initially thought about investigating the fuel system but I stumbled onto this thread and decided the ECU was the obvious starting point. I also couldn't reason how restarting the car would 'fix' a fuel delivery problem. Regardless, a fuel filter is cheap enough and worth doing so it's going on my list - along with spark plugs.

Speedy - can you please post a scan/copy of your receipt from the dealership so we can see specifically what 'related sensors...and other parts that are in relation to pumping fuel from the fueltank to the engine and "giving" fuel "back" to the fueltank" they serviced? Maybe it's not in English but could translate the components for us?

[flash213]

I found some intresting information that falls in line with LS Bob's diagnosis on this web site http://auto.consumerguide.com/Auto/Used/re...iewreliability/

The site claims the " engine misfire" can be fixed by replacing the ECU the cruise control module and spark plugs.

Honestly I have not been able to replicate the problem for my 95. I did recieve my 89661-50224 yesterday and will go ahead and give it a try. I am also switching from a Cali ECU to the Federal. If anyone has a tutorial on how to change it out I would appreciate it. I will follow up with an update soon.

By the way I picked up the ECU for $225 from car-part.com with a 60 day refund policy.

[95LS400Bob]

Technical Service Bulletin.

←

OEM = Original Equipment Manufacturer

Once I got my ECU back from upgrading at Auto & Truck in FL I went for a short (5 mile) drive to be sure the car ran OK. The next time I drove it was a few hours later when I went to the airport to pick up my wife. The car died at the airport exit which was 32 after miles of 70MPH driving. The new ECU only had 47 miles on it and it was showing the same symptoms. It idels down to 200 or 300 almost every day on my way to work after a non stop 17 mile trip at 70MPH. It may only die once or twice a week on that leg of the daily trip.

I had always wondered if this issue was related to aging parts - otherwise it shoudl have been more visible at time of purchase and Lexus woudl have been in for a recall and/or a lot of customer dissatisfaction - a lose-lose for them and the owner. I initially thought about investigating the fuel system but I stumbled onto this thread and decided the ECU was the obvious starting point. I also couldn't reason how restarting the car would 'fix' a fuel delivery problem. Regardless, a fuel filter is cheap enough and worth doing so it's going on my list - along with spark plugs.

Speedy - can you please post a scan/copy of your receipt from the dealership so we can see specifically what 'related sensors...and other parts that are in relation to pumping fuel from the fueltank to the engine and "giving" fuel "back" to the fueltank" they serviced? Maybe it's not in English but could translate the components for us?

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If you really want to clear that it is an idle issue and ECU issue, then here is a test for you. This is what I would do.

Record the idle rpm with the car in gear and foot on the brake. It should be around 600 rpm.

Now go drive to the same place it died on you....the airport....only this time you know it is going to die. So...hold your foot just slightly on the throttle peddle as you stop. Hold that rpm to around 600 rpm with your foot.

Now..let off the throttle. You'll probably see 200 rpm or a slight engine surging...and then the engine will die. Let it die.

Turn the key off, then restart the car. Back in gear and foot on the brake. Got 600 rpm again? Then it's an ECU problem. You just reset the ecu when you restarted.

Spark plugs, fuel filters and such do not "come back" with a restart of the engine.

And I agree...I think it is and "age" problem with the electronic ECU.

[yoichisoma]

Hello,

Sorry I was on a trip to Tokyo so I have not been able to respond. I got my ECu back from Auto and Truck Electronics in Fla. I was driving around to test today and it seems that the jerking is quite a bit better but the engine dying out after a long drive issue is still a problem. It did not die on me as I did not go on a long drive, but the idle was very low at aprox 400. It should be around 550 or 600. So Indeed I am perplexed. Should I go for a 89661-50224 or should I seek a new cruise control computer and spark plugs? This is the TSB for "to improve driving smoothness at speeds above 40mph." Nowhere in the TSB does it mention stalling after a freeway drive. Anyway, I am going to change some hardware today including all spark plugs, wires, dist, rotor, and ignition coils (2). Also I got the throttle body off and I am going to clean it.

Please, if anybody has solved this issue completely, tell us what you did.

Yo

[95LS400Bob]

Lexus never did admit a problem with the engine dying after a long drive. Several members I contacted had the dying issue and got the new ECU's and it solved the problem.

My issue and several others was solved by changing the ECU.

But...I think everyone had a "normal" idle of 550 to 600 rpms at all other times. If your engine idle is less than that then perhaps ther eis another problem. Do the test above I listed after the long drive and see if you can keep it running with foot on the throttle...as I described.

The "jerking" issue. Mine does it very seldom with the current ECU I have in the car. It used to do it all the time. Two other members bought rebuilt ECU's from Auto Truck Electric and they both said the jerking went away and also the dying isse. Both these cars were 95's.

[flash213]

Just an update. I have been using the new ECU (89661-50224) on my 95 for about two weeks now and no problems so far. I swiched from a California ECU. Noticed a modest increase of quickness which was a bonus. Hope this helps.

[LEGENDICON]

hey whats up guys does any one here know where i can get a "Idle control Valve" new or used for a 93 Ls 400 I believe 90-94 will fit. .other than the dealer cuz they want damn near $ 900 for it which is rediculous. PLEASE HELP my car is off the road because of this problem because of stalling and studdering while giving it gas , not drivable plus i dont want to hurt the car. If you can help me either respond here or you can email me at nyinfamous2k2@aol.com i appreciate it.

[95LS400Bob]

Park Place Lexus shows Idle speed control for $525.79. 93-94 Ls400 only.

Be brave. Take it apart and look at it. I did and there was nothing wrong with mine. Might be electrical connection or ecu instead.

[95LS400Bob]

What we thought fixed the problem did not. Or maybe it went back to dying. Read my previous posts in this thread and then this update below:

In recap:

My 1995 Ls would die after a highway cruise of 20 minutes or more. I suspected an ECU problem because all else checked out. I changed the ECU (which was a cal emissions model) to a 49 state emissions model and picked up power and mileage.

A test drive of over 60 miles after this change and the engine did not die, I figured the problem solved. But now it is back.

I had to go on an 1150 mile trip Saturday...in fact...over the same highways where the Lexus died before. The first town was 70 miles away and the Lexus was idling fine this time (where it died before). :)

I figured again....I had fixed the problem.

But the next town at 140 miles into the trip...It died while making a slow left turn in town. Started right back up and idled normally. Just like it never happened.

So from there...I started to watch that idle rpm in each town. All I can say is that it takes longer (more miles traveled) for the "dying" to happen.

However....we have discovered that if the climate control is in the auto position and therefore the air conditioning compressor is engaged....the engine will not die.

:whistles: It just so happened it was 104 degrees where we were going and as long as the ac was on...there was never a problem. I know this sounds nuts...but it is true.

The car runs perfectly and mileage is great with no other problems. I have rigged up a testing device to help me catch what is happening when the engine dies after the highway cruise. I don't give up and I will find it. Just stay tuned.

[morg96ls400]

What we thought fixed the problem did not. Or maybe it went back to dying. Read my previous posts in this thread and then this update below:

In recap:

My 1995 Ls would die after a highway cruise of 20 minutes or more.  I suspected an ECU problem because all else checked out. I changed the ECU (which was a cal emissions model) to a 49 state emissions model and picked up power and mileage.

A test drive of over 60 miles after this change and the engine did not die, I figured the problem solved. But now it is back.

I had to go on an 1150 mile trip Saturday...in fact...over the same highways where the Lexus died before. The first town was 70 miles away and the Lexus was idling fine this time (where it died before).  :)

I figured again....I had fixed the problem.

But the next town at 140 miles into the trip...It died while making a slow left turn in town.    Started right back up and idled normally. Just like it never happened.

So from there...I started to watch that idle rpm in each town. All I can say is that it takes longer (more miles traveled) for the "dying" to happen.

However....we have discovered that if the climate control is in the auto position and therefore the air conditioning compressor is engaged....the engine will not die.

:whistles:  It just so happened it was 104 degrees where we were going and as long as the ac was on...there was never a problem. I know this sounds nuts...but it is true.

The car runs perfectly and mileage is great with no other problems. I have rigged up a testing device to help me catch what is happening when the engine dies after the highway cruise.  I don't give up and I will find it. Just stay tuned.

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Could this be a faulty engine temperature sensor not telling the ecu how much fuel to give at different temps? Sounds like it must be something not talking to the ecu during these conditions. I have the same problem with my 1996 ls400 and it just started happening a few weeks ago. Gonna replace some stuff (fuel filter, pcv) myself, and then have engine temp sensor done to see if this helps. Really annoyed that this problem was not found by lexus and recalled.

[95LS400Bob]

A fuel filter, engine temp sensor or pcv valve if faulty would cause problems.....but would have nothing to do with the "20 minute highway drive or longer" before acting up.

Haven't gotten time to take another highway cruise for the problem to happen so I can try to catch the problem. The wife drives the car every day...all over town...and never a problem.

[chrisnisbet]

Hi

Well, you can add me to the list of '95 LS400 owners that has see this problem.

It is exactly the same as the problem described by 95LS400Bob. At first, I thought it was a one off, but when it happened a 2nd, 3rd, and 4th time after driving for a long time at around 60mph, I suspected a problem with the car.

For me, if you just come to a complete stop, without turning the wheel (no power steering effort required), you could see the car sit with an idle of around 200 rpm.

After a few seconds, you can see the idle speed creep up incrementally until it reaches the normal idle speed (~600rpm).

I have a background in control systems, and this symptom appears to be exactly like something we called integral windup. Integral control action is used to correct for an error in the coontrolled variable from the setpoint.

It looks like because the engine speed is way above the idle setpoint (600) for such a long period of time, there is enough integral windup occurring that when the throttle is completely released, the idel control valve is being closed off almost completely for a period of time.

It looks like this is the general consensus.

The ECU model #: 89661-50224 works better than some other one, although it appears that changing to this ECU may not work in all cases.

Is that correct?

It is possible to reFLASH the ECU to basically upgrade it to 89661-50224 spec, although you have to send the unit off somewhere to get this done.

Has anyone reFLASHed their ECU themselves?

My LS400 has done just over 50K miles, and comes with some kind of warranty, and was bought (as an import) from a Toyota dealer so I might just check the warranty and see if Toyota will come to the party and help me sort this problem out. It sure seems like the sort of problem that could cause some safety issues, and can't be a good look for a luxury car.

[95LS400Bob]

My original ecu 50231 did it. I changed to a 50221 and that fixed it. But then it went back to dying again.

Since I have had my throttle control valve apart and checked it in every way I still believe this is an ECU issue.

If it were a reflash issue then everybodys car would be dying that didn't have the reflash and that does not seem the case. I think it is a component issue inside the ECU...something breaking down. The only way I know that I could help prove this is to drive the car on the highway until it get's to it's "dying mode". Keep the car running by light foot throttle and pull it safely off the road and then let it die. Then take the idle contol valve apart and check that it is closed (or nearly closed...thus the 200 rpm idle).

Rather than chase ECU's I may come up with my own throttle control unit.

[flash213]

I just wanted to throw in that I have been on several highway trips since changing to the 89661-50224 ECU in late April and no problems. I have several more highway trips over the next few weeks so if anything changes I will certainly post. I hate to see this thread keep poping back up. Hopefully we can nail the problem down.

[95LS400Bob]

I just wanted to throw in that I have been on several highway trips since changing to the 89661-50224 ECU in late April and no problems. I have several more highway trips over the next few weeks  so if anything changes I will certainly post. I hate to see this thread keep poping back up. Hopefully we can nail the problem down.

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So in reading your posts:

1. You had the dying problem on a 1200 mile trip.

2. You changed your cal ecu to a 49 state ecu 50224.

3, This fixed the dying problem.

Am I correct?

[flash213]

That's correct. To this point it hasn't happened again.

[LEGENDICON]

Ok. Im the guy with a 93 Ls 400 with the same problem as you 95ers and im on the very of insanity now fellas. So here we go; so far in effort to correct this problem i started small and inexpensive and worked my way up. I have replaced the spark plugs, wires, oil filter , fuel filter, air filter, caps, and rotors, NOT FIXED. So I cleaned the throttle body, and replaced the Air Flow Meter. NOT FIXED. now i just had the dealer put in a new idle control valve where they said that was definalty the problem. funny, they were wrong, because I stalled out on the way home from the dealership. So back the car went, they are currently running all types of tests and diognostics on it. hopfully there genius mechanics will resolve this problem and I can report good new with the cure to all of you. but any1 come across some answer please keep us all posted.

[chrisnisbet]

I haven't checked the ECU model in my car yet, but I'll let you know when I have. My car is actually from Singapore (I'm in N.Z.), so I'm wondering which model ECU I have.

I too believe that there is some kind of issue relating to component age, and the idle problem only becomes apparent after the car has done some significant mileage.

Perhaps we have a combination of ECU code limitation, fuel supply (filter?) issue, ICV getting dirty, blocked air cleaner etc.

[95LS400Bob]

I haven't checked the ECU model in my car yet, but I'll let you know when I have. My car is actually from Singapore (I'm in N.Z.), so I'm wondering which model ECU I have.

I too believe that there is some kind of issue relating to component age, and the idle problem only becomes apparent after the car has done some significant mileage.

Perhaps we have a combination of ECU code limitation, fuel supply (filter?) issue, ICV getting dirty, blocked air cleaner etc.

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I also wondered about a combination of problems...but....the car runs perfectly and idles perfectly at all other times. No other issues whatsoever. If I had different issue like air filter, dirty icv or fuel supply probelms...surely I would think I would see some type of problem at other times.

[chrisnisbet]

Yep, when you think about it, you can probably rule a few things out as being the cause, and you'd probably see other symptoms as well, not just this stall that instantly disappears once the car is restarted.