jesse hall

i'm having a re-occurring problem that noboby seems to be able to diagnois.
i gave my son our 91 ls-400, and while driving the engine will just shut down. seems to be a temperature related issue, however the car is not overheating at all. The car will always start again, usually right away, but sometimes takes as much as 2 minutes. only happens when ambiet temps are above 80 f , and with the a/c running. very occasionally this happens while driving, but usually only while at a stop or very low speeds.

thanks for any help we can get.

skperformance

iTrader: (6)

Every try pressing the gas pedal while starting after the shut down?

DoubleWhoosh

It's possible to be a problem with the Mass air sensor or fuel pump ecu, but those are only guesses.

Problem with complicated cars like this when they get older, especially intermittent problems, is they are hard to chase down.

Just weigh out also if you want to keep the car for a while still, then you might be able to justify changing stuff out even if it doesn't necessarily fix the problem.

Had a problem with a jibbering customer a little while back that thought I promised him that changing 2 things would magically fix everything, but that would be a foolish promise at the very least. Just have to take some educated guesses, try to test them (if that's even possible), and try your best to diagnose it (along with some luck and some crossed fingers too!).

The mass air problem sometimes you can do limited testing by tapping it, jiggling the plug, unplugging it to see if it behaves the same (at the time it stalls out).

Sometimes it might also be a problem with a cam or crank sensor signal, or even the main ecu itself.

Kansas

This has happened several times (every 3-4 years) on the 90 LS we had for 14 years and it happened on our 2000 LS in 2004. In all instances, the problem was the battery - a broken connection between the cells. Usually the engine would die when turning a corner or after hitting a bump. When it happened in 2004, I didn't even bother to have the battery tested - I just popped a new one in and that solved the problem.

biglexass

this happend to mine but i rule out the problem.next time try driving around with the ac on the turn it off.if it stalls then you know whats going on.when i trun my ac off at the next time i come to a complete stop the rpms just drop all the way and the car shuts off.its weird and my buddys at the dealer ship could not even figure out what it is.

DoubleWhoosh

Very rare problem, and also strange, as the car does not need a battery to run. If anything, something like this was basically causing a dead short across the + and - terminals, with the potential to cause some severe damage to all of the electrical components in the car, especially the gauges, ecus and alternator!

DoubleWhoosh

Can try cleaning the throttle body and IAC valve with some brake cleaner or carb cleaner. That might do it.

Kansas

Actually, DoubleWhoosh, the owner of the independent shop (Exact Performance, Shawnee Kansas) that maintains our cars told me that this is a common problem on an LS and is related to the high load an LS places on a battery. Yes, the problem could be something else. A trickle charger with a meter can tell you quickly if the battery is defective.

GRAND_LS 4

iTrader: (2)

Yes. I've driven the car without a battery once, and it was not pretty. The car shook very violently whenever I turned on my lights, and the same way with any other major electrical accessory.

jesse hall

To every one who has posted a reply, thanks. But i'm still having the same problem, Not the battery,ecu or mass air sensor.
I had a similar problem on a 89 Maxima, after an exhausting search i finally found out that the car had a teperature sensor that only reported back to the ecu, it failed or got out of calibration and would shut the car down at normal operating temperatures. once found and diconnected,the car never had the problem again.

does anyone know if the lexus uses one. i've found that nissan and toyotas are alike in many ways under the hood, not to offend anyone.

johndeuce4

Hi Everyone. My 1997 LS 400 (130,000 miles) was in the shop 14 days. Car cut off in traffic. AAA Club got restarted tapping on fuse box. Hazardous drive home. Towed to shop next day. This shop replaced the fuel pump and relay ($975). Supposed to be $1200, but problems with locating the part and other mix-ups (14 days without the car). 2 weeks later, same problem. Car quit in traffic. Towed to same shop. They now say fuse box, lose connector OR fuse box housing. Once again, problems finding parts. This is actually the THIRD time car stalled while driving. Another shop had the car 10 days, but car ran fine. They gave the car back to me. Intermittent problems, problems that don't repeat such a pain to solve. When my part comes in, fuse box housing should stabilize any loose connection, but will I ever feel confident driving in traffic again?

Dezdez

Have the same problem on my 94 LS. Last week car did exactly as you posted, got home and parked it. The next day tried cranking it and it wouldnt even start. Left it alone for a couple of more days without the battery in it (had to charge it). Replaced the battery and the car started like nothing and worked great for a week more before it doing the same thing. I had by then replaced the battery and cleaned the terminals. Have it parked again without the battery connected. Going to try and turn it on tomorrow and see if that works. I have been reading threads and when it comes to this type of sympton it could be fuel or spark and that is being general about the whole components that make up the electrical and fuel system. Just ordered some parts from rockauto yesterday too...should of ordered the fuel filter and ignition coils dammit.

johndeuce4

LS 400 has been repaired - finally. Did the repair solve the problem? Only time will tell. As I posted, I paid for a new fuel pump and fuel pressure regulator ($975 - reduced from $1200 because of delays/mix ups). When car stalled again, after lengthy diagnosis, was told I had a loose connector to the fuse box. That made sense, because the AAA Club driver banged on my fuse box and the car restarted. I had to drive home using gas and brake or car would die again. So, the repair shop said I could take the car home, just be careful not to cause the loose connector to the fuse box to become jostled around until the a fuse box housing could be ordered and installed. It took about 3 weeks to locate and receive the housing that would stabilize the connection. The part came in, took about 3 hours to install. Now, what about the $975 I already paid for a repair that didn't solve the problem? My initial paperwork shows the repair tech noted the fuel pump and regulator were likely to fail in less than a year because of the undue stress from past few weeks. But, the shop said just pay for parts, not labor - $40. I have been driving car for about a week - trying not to worry about "dying in flight". So far so good. Maybe after a month I will feel more comfortable. As they say, a car problem that is intermittent is hard to diagnose/solve. The internet shows multiple reason a car will quit cold while driving. So, hope I am on the road to healing.