Wang751

I have a 1991 LS 400.

Changed front brakes 10 days ago. The next day, the car died in front of the traffic light. I was able to restart it. This happened a couple of times before it died completely last Monday after I drove it only 5 minutes and pulled up into a parking lot. All indication lights were on and I could crank it but no fire. I had to tow the car to a mechanic.

The mechanic couldn't start my car the next morning either. Then he unpluged and repluged the main relay, and another relay, and the car started running. He changed the two relays. I drove the car for two days before it died again.

The mechanic told me that the computers showed nothing wrong with my car and he suggested that I tow the car to him again to change the spark plug, wires and other electronic parts one by one, until the problem is gone. I am hesitate to do so since he could not find out where the problem is. I just did what he did: unplug the relays and replug them in, and the care started again.

Anyone can suggest what the problem is?

Thanks.

persian451

well you could start with the battery.. the mechanic should have started there... there could be a dead cell that wont let the alternator from starting... or its teh alternator not function... spark plugs and wires are stupid to chagne.. what an idiot for a mechanic.. always trying to rip people off..

Lex Tech

Your mechanic needs to check the ignition & fuel system sounds like. It sounds like you're either loosing fuel or ignition.

loonyrobert3

the same thing happened to me in my dads expedition after we took it to a mechanic he had it for 3 days and then ask for our second key to start the car and the problem was the first set the key went bad.they have some sort of chip wit a liquid and the liquid had disappeard i think it dripped out cause the key was broken.hope this works for you.good luck.

robert

Lex Tech

The LS didn't receive an engine immobilizer until 1998.

Wang751

Thank you all for your advices.

When the trouble started, the mechanic was able to restart the car by unplug the relays and then put the relasys back. I did the same when the car died a second time. I believe by doing so, some electonic devices was reset to its working condition. Has anyone over there had the same problem before?

The battery was working since I was able to crank the engine when the problem occured.

The wires and spark plugs are also working because when I reset the relays, the car could run without problem.

I tried to start the car a few times in last two days, every time it started without problem. I just don't know when the car will give up again.

Lex Tech

Do you know which relays you unplugged?

This sound like a similar problem I had was a 91 LS a few months ago. They towed it in and said it wouldn't start. Of course when I got in it and tried it, it crank right up. The engine had a bad miss to it ... I pulled the plugs and found they were fouled out, along with original spark plugs wires so I replaced them and let them have it back. Two weeks later it came back again ... the customer said it wouldn't start; I get it turn the key, it cranks. This time I drove it around for a while to see if I get it to cut off ... Nothing. So I park it in a stall beside me and watch it. Eventually it cuts off.

I found that the coils were loosing power, and traced the problem to a corroded connector at a junction box near the air cleaner. I'm not saying that this is your problem, but your mechanic needs to check to see what your car doesn't have next time it cuts off. Fuel or Ignition....

See if you can find out what relays you're pulling out to get it to restart. This just may be a coincidence that it restarts after pulling those relays

Wang751

Thanks, Lex Tech, for pointing me to the right direction.

My mechanic replaced two relays. Here are the words and parts numbers I copied from the relays:

1. RELAY ,TOYOTA, 90987-04002, 056700-6780, 12 V, DENSO
2. TOYOTA RELAY M4, 90987-02004, DENSO, 056700-4810

He told me that he replaced the main relay and another relay.

I tried to call him but couldn't reach him; it's sunday today.

Lex Tech

Where were these relays pulled from? That could help determining they're function. I'll check the part number on these relays tomorrow at work to see if they're specifically for one function or just relays in general.

Wang751

Lex Tech,

Thanks again for your help.

The relays were pulled from the black box between the battery and the coolant reservior.

Colors of the two replaced are black and silver.

Wang751

Lex Tech,

The problem finally is solved. Longo Lexus checked my car and found that one wire connected to EFI was disconnected. They reconnected the wire and that was it. The car has been running without problem ever since.

A year and a half ago, I replaced rear brake pads at the same place and the generator went dead a week later.

They asked me that if I changed the generator when I went to replace the front brakes this time. There should be some connection between these repairs.