Car Randomly Dies When Driving.

[SC4Hundred]

Hi, i'm new to these forums and this is my first car. I don't know much about cars; however, as more problems occur with this car, I learn something new.

Anyway, my SC 400 randomly dies when i'm driving. It started happening last week. I've read that it could be multiple issues and so far I haven't found a solution. Anything that I can check myself to start, please let me know.

[fhb5032]

UHHHH, just how is it resurrected? No, seriously. Can you describe what's happening?

Do any of the accessories, lights, etc still work? Does the check engine light come on?

Does it re-start right away or after some time?

Does the engine "crank" when you try to restart it? What does happen when you try to restart it?

Is every "death" and resurrection just the same sequence?

[1990LS400]

Great questions from fhb5032.

My main question is does the engine shut off as if it is being turned off with a light switch instead of sputtering and dying? At what speeds are you typically traveling when the engine shuts down. Are you turning a corner or have you hit a bump or pothole just before the engine shuts down?

And, yes, does the engine start back up easily?

The reason I ask these questions is that a failing connection between battery cells can cause an engine shutdown and can be triggered by hitting a bump/pothole or turning a corner. Or it could be a failing alternator which is often caused by a failing power steering pump leaking fluid on it.

You might see if there are any stored problem codes using the procedure at http://www.lexls.com/tutorials/intro/codereading.html

[SC4Hundred]

UHHHH, just how is it resurrected? No, seriously. Can you describe what's happening?

Do any of the accessories, lights, etc still work? Does the check engine light come on?

- My lights still work properly. The battery and oil light come on when it dies.

Does it re-start right away or after some time?

- It cranks back up every time. Sometimes it will die soon after and will die quicker if I give it gas. Sometimes it will crank up and drive like nothing was wrong.

Is every "death" and resurrection just the same sequence?

- Yes it is.

Great questions from fhb5032.

My main question is does the engine shut off as if it is being turned off with a light switch instead of sputtering and dying? At what speeds are you typically traveling when the engine shuts down. Are you turning a corner or have you hit a bump or pothole just before the engine shuts down?

- Yeah, as if it was being turned off with a light switch. The car doesn't sputter, it just dies. The car will die mostly when I stop, slow down, or cruise at a low speed. No, it hasn't died while turning corners, and no bumps or potholes have been hit to know.

And, yes, does the engine start back up easily?

- Yes, it does.

[1990LS400]

The first thing I would check is the condition of the battery - any idea how old it is? In 23 years of driving Lexus V8 cars, I've rarely had a battery last more than 4 years and some have lasted considerably less time ... on only about one year. You could take your battery to a store that sells them and have it checked. And not that it is going to solve your problem, but make sure that the battery terminals and cable clamps are bright and shiny and spotlessly clean - corroded terminals and clamps can interfere with battery charging. A terminal/clamp cleaning tool is a few bucks at an auto parts store. Baking soda mixed with a little water can help clean battery terminals and cable clamps - I use an old tooth brush.

Also check to verify that the bottom of the power steering pump is free of dripping fluid that could be leaking on the alternator. If the power steering pump fluid level is low, that might indicate a leak.

[1JZPWRD]

Sounds like it could be many problems. I would first do the fuel ecu mod. This allows the full pump to work 100% in any engine temperatures. I would also lean toward a bad coil(s), plugs, wires, IACV, MAF, 02 sensors, clogged cats, and faulty fuel ecu. The fuel ecu is in the driver side rear comaprtment, under the glass. I would first pull the codes, and poist up your findings, if any. I also have the PDF manual with over 4K pages, if needed. Have you personally checked the timing?

[sule]

_{Fuel pump ecu is going bad.Buy one from Ebay and you can do it yourself.Just as one member said It is located behind the driver seat below the quater glass.Pull the back seat bench,remove the panel and it is right there.}

[SeanGrac]

it's not the ECU

[fhb5032]

I've experienced similar problems with non-working gasoline vapor controls. If it's not working properly, as gasoline is taken from the tank, a vacuum develops that can cause fuel starvation.

I don't know enough, yet, about ecus in pre-ODB II 90's era Lexus to know if this would set ecu codes or a check light. I doubt that it would, but the next time it happens, loosen or remove the gas cap and listen for a hiss. If you hear one, then this is a possible cause.

It's unusual, but worth investigating.

[jasmine1200]

I'm having the exact same problem as listed above, with my own 1994 SC400 (sounds like exactly the same problem -- all the way down to the replies listed in red in the quote).

Oh, except that in my car's case it does NOT always crank back up again after it stops, unfortunately!

So far the mechanics have 1) cleaned out the idle air pressure valve, which didn't work; and 2) replaced it, at a cost of $1000. It looked like that might be working, for about a week...

Until yesterday, when I tried to pull out of a parking lot after a short stop and the car died just as I tried to start it.

Did SC4Hundred ever find a solution, or does anyone else have further ideas?

I do a lot of long-distance driving and it's quite scary to never know if my car will continue to run or die at a stoplight. So I'm seriously considering getting a new car. (Interestingly, the problem seems more likely to happen after I've driven a fairly long distance at highway speeds, and then stop).

The mechanics are kind of at a loss with this one -- they've tried a bunch of different things and say that the only thing left to check is whether it's a computer problem... which sounds like a MAJOR fix.

Both the battery and the alternator are brand new.

I'd be really grateful for any ideas -- thanks!

UHHHH, just how is it resurrected? No, seriously. Can you describe what's happening?

Do any of the accessories, lights, etc still work? Does the check engine light come on?

- My lights still work properly. The battery and oil light come on when it dies.

Does it re-start right away or after some time?

- It cranks back up every time. Sometimes it will die soon after and will die quicker if I give it gas. Sometimes it will crank up and drive like nothing was wrong.

Is every "death" and resurrection just the same sequence?

- Yes it is.

Great questions from fhb5032.

My main question is does the engine shut off as if it is being turned off with a light switch instead of sputtering and dying? At what speeds are you typically traveling when the engine shuts down. Are you turning a corner or have you hit a bump or pothole just before the engine shuts down?

- Yeah, as if it was being turned off with a light switch. The car doesn't sputter, it just dies. The car will die mostly when I stop, slow down, or cruise at a low speed. No, it hasn't died while turning corners, and no bumps or potholes have been hit to know.

And, yes, does the engine start back up easily?

- Yes, it does.

[sule]

I fix mine by replacing fuel pump control unit.it is located behind the driver's seat. Just remove the panel below the quarter glass window.You can buy one on ebay for about 60.00 bucks.

[lenore]

The fuel pump itself could be bad, a friend of mine had same symptoms and replacing fuel pump fixed it....

[DUTH69R]

Hey yall After reading a bunch of threads. I have a 92 sc400 while driving it shut off and would only give spurratic ignition pops.

So far i've checked fuel pump runs and produces 45lbs min.

checked timing and all related parts cam pos sens. 2 replaced

crank pos sens

replaced both ignitors

checked ecu........ had atrace burnt inside------- replaced ecu

now it will idle somewhat but will stumble and die if throttle is move much

unplugged TPS and MAF and it will now idle smooth. plug in either TPS or MAF and it dies within a few seconds. i just installed a USED MAF and it made no difference. a bunch of people keep saying FCU but i am tired of chasing a ghost.

i did take it to my local Lexus Dealer and was lied to by them . i have been building cars for 30 years and have just gotten stumped and fed up, their lil lie cost them about 90k in lost business that day alone. I now use a Dealer in Ga..

i need some help and insight Thanks

[rsamuel]

Hey all,

So I had a problem that may be the same as a number of you. Others sound like they may have a different problem.

Intermittently, usually just after lifting off the gas pedal, the car would die. It was also idling rough, and low, and sometimes moving between 500 and 1200 rpms regularly like once per second (very rough idle).

Giving it gas almost always would stop it form dying, but i would ahve to sit at a light with left foot on the brake and right foot trying to help the idle stay up.

A number of theories proved incorrect: Failed power steering pump (yes I have rock hard arms now), failures in the electical systems (fixed but no effect), and others.

Then I thought about the fact that I almost always get gas at the same place. One day I went somewhere else, a more expensive gas station, and threw in an extra container of fuel injector cleaner and engine cleaner stuff that is supposedly in all these gasolines anyway. Think Chevron Techron, Shell V power, etc. Anyway, the problem hasn't recurred since that fillup and since I stopped going to the chevron by my house.

We all know, I assume, that the engine needs high octane (premium gas). In fact it calls for 93 where I can usually only find 91 and that's in San Francisco, not Santa Fe. I am suspecting that that chevron gas either was not the rating it claimed, or did not contain the techron. I had been going there for years. probably 19 in 20 filllups happened there. The car has 200k miles on it, and I think giving it lower quality gasoline especially without the cleaning additives doesn't manifest immediately, but slowly, and if the octane rating is a little low, it may just not give the engine the power it needs and probably confuses the idle computer, etc. And obviously if the detergents and other additives aren't in the gas, it's going to muck up slowly.

So my suggestion: Fill it with one of those Lucas fuel injector cleaner bottles and some nice premium gas from a nice gas station. I bet it stops happening.