DasDream

Hey all!

My name is Tyler, I'm new here and I bought my first Lexus about 4 months ago from a buddy. Some info: 1992 Lexus LS400 - 268,000 miles - MB Battles 18" wheels - Meagan Racing Coil overs

The car was fine for awhile then started having these problems at first:

1. slight misfire/hiccup when accelerating and engine was under heavy load.
2. Transmission shift problem. It would shift fine when cold but once car warmed up it would shift from 1st to 3rd and OD drive light would flash if Overdrive button was activated.
3. parasitic draw and battery would drain to 8 volts no matter how much time it sat ( 4 hours, or 4 days)
4. AC/ Heater blower motor would not work on any setting (low, medium, high)

Remedies I've done:
Replaced spark plugs(NGK), plug wires(NGK), Driver and Passenger Ignition coils(NGK), Driver and Passenger side Distributor Cap and Rotors (Beck Arnley), and a new battery.
Took the alternator out and had it tested at two places. It is good and so is the voltage regulator. Took it apart and cleaned everything then reinstalled.
Checked all the fuses, they are good, and tested the blower motor outside of the car with 12volts and it is good too.

I drove the car for a while after doing all this and the misfire, shift problem, and parasitic draw remained. I ended up just manually shifting the car as to not bog down going into 3rd and not driving it hard so it misfired. I would remove the negative battery cable every night so the battery wouldn't drain. Randomly one morning when on the way to work I put the negative cable back on, car got power. I tried to start it and there was no response from the ignition switch, no click from starter, no power dim. Nothing at all. Checked the battery and it was at 12.5 volts. Fuses were good and the cables were tight. Cycled the key again still nothing. Tried it one more time and the car started so I drove to work and unplugged the negative cable. Got back from work 10 hours later, plugged my negative cable in, tried to start and same thing. No response from the ignition switch. Battery tested 12.5, fuses were good, and cables were tight. Internet said maybe starter motor was bad so I tried to bang it with my long breaker bar and still got nothing. I remembered I had unplugged my antenna motor earlier that week thinking that was the parasitic draw because it was stuck and wouldn't go up or down. I reconnected the motor and still no response from the ignition switch. I let it sit for about 2 hours while I talked to my girlfriend and tried a jump start with nothing. We were about to leave and get a tow when I said F*** It im going to try the key one more time. It started! WTF. So I came to the conclusion that maybe my starter was either bad or the wiring was bad. Long story short, I removed everything and got to the starter motor. Someone had left the bolts super loose and it was able to flop around pretty bad. I took it out and had it tested as good multiple times. I took it apart and cleaned everything inside of it. Reinstalled and put everything back together. New O rings and caps on injectors, new gaskets, new coolant lines and hose clamps. I broke the side wiring harness plastics trying to get it out of the way so I used wiring cover and electrical tape. Everything went back in, all plugs back in. I had taken the ECU out to inspect it and had it sitting on my desk for about 2 weeks. I did take it apart and change out the capacitors using the guide from LScowboyLS and did find a trace on the board broke so I ran a solder bridge over it to fix it. Now heres where im at.

1. ignition switch is still iffy. Sometimes it works and cranks the motor and sometimes I have to jump the starter relay to crank the motor. When it works, the two fans up front will run when in the on position. And when the ignition switch won't crank, the fans won't run
2. The starter is working fantastic now I am getting fuel to the rails but I am not getting any spark. Tested the wires, caps, and rotors all the way to the ignition coils and I am not getting spark coming from the ignition coils on either side. The ignition wires get 12v with key in on.
I checked my crankshaft position sensor. It was covered in oil but I cleaned it and confirmed it is putting out voltage when I move a metal object passed it. I'm thinking this is the sensor design that sends signal to the ecu. The wiring was bad so I resoldered some new wire to the sensor plug. Not sure how to test the wires to see if they have resistance and are going to the ECU.

I am running out of brain juice and have been working on this car for like a month now. I wan't to say that either I messed up some wiring in the harness when I moved it around doing the starter, or that I messed up the ECU somehow by removing it and having it sit on my desk. I made sure to discharge static before soldering the new caps. I'm not sure how that copper trace was broken because I hadn't open the ecu before and was very careful moving it around. There was no resin over the top of that trace like everywhere else. Essentially I still have an intermittent ignition switch problem which requires me to jump the starter relay to crank, and I'm not getting spark. Not sure what to test now and how to test for bad ECU. I could buy a used ECU off ebay but I'm running low on money and time. No cars at my local junkyards had ECUs. I checked. Bright side is I bought double the Caps so I still have enough to solder new ones onto a replacement ECU if needed.

Sorry for long post and rant. I'm exhausted. PLEASE HELP

fixmiester

You've done a lot of good troubleshooting, but I suspect a problem with your keyswitch. It may have other connections besides just the starter relay; bypassing that was a good idea, but there are other signals that go through/to the immobilizer, and to the ECU. Get a wiring diagram and look for other circuits that allow the ignition to be enabled, when the engine is cranked. Bad connections at the keyswitch are another possibility.

oldskewel

iTrader: (1)

Sorry, I did not read all the details carefully.

But I'll suggest that problems 1+2 can be caused by many things, including a general electrical problem - i.e., there may be nothing at all wrong with the engine or AT.

Problem 4 is a separate issue, and I'll suggest to isolate that until you've solved this problem by working on other stuff - so pull fuses, etc. as needed to completely isolate the HVAC. So the concept is that if there is a problem in the HVAC anywhere, you want to make sure it is not causing electrical problems outside of HVAC.

So I'd focus on 3. Regardless of store bench tests or newness of parts, I would consider everything a suspect and track that down carefully. An intermittently failing battery can cause problems - one easy way to test that if you have a spare or a compatible second car, is to swap batteries and see if anything changes.

Good luck.

Bprakash

When spark plug wires are changed, the wires can get snagged and cut inside the belt cover plastic due to improper wire retainers. This will cause misfire upon acceleration. Open up and check.

oldskewel

iTrader: (1)

I can believe that. Great example.

While that may be true, there is no way at all that a problem with the plug wires is draining the battery or causing HVAC problems.

So some strategic thinking in troubleshooting approach should help, and is what I was suggesting two posts up.

You might ALSO have this plug wire problem, sure. But since you know you've got the general electrical problem, focusing on that first may get you to a solution more quickly.

BTW, a cig-lighter digital voltage gauge (about $2 on eBay) is something I've found to be a good easy way to always monitor your car's electrical system. If you're lucky enough to start using one when everything is good, you'll more easily know when something is wrong - i.e., you'll know what voltage should be when you first turn the key to ON, when running under different conditions, and when turning the engine off after a drive.

DasDream

That was something I was getting too. The way the key switch will work then randomly not work stumps me. Is that something the ECU would control? or possibly there is a very loose wire that is having intermittent connection. I'll have to look at how to get it apart and see whats inside. Any suggestion on where to find good wiring diagrams for this car? Also from my research, I thought that the 1st gen ls400 didn't have an immobilizer. Thanks

DasDream

I'm thinking the misfire and shift problems are either ECU related or wiring related. The misfire isn't consistent so makes me think a wire is shorting temporarily. and the shift problem doesn't exist when the engine and transmission are cold but after driving and it warms up it will start skipping 2nd. So ECU, wiring, or maybe my transmission needs a flush/ maybe a shift solenoid is going bad once warmed up. I agree with you and appreciate your advice to disable everything HVAC related so as to cross it off for now and see if its affecting anything else electrical.
I think my parasitic draw was from my starter motor not being bolted all the way down so it didn't have a good seat against the motor. I stated that in my post that you didn't read all the way but since I can't get my car started since doing the starter motor (can't get spark from ignition coils to spark plugs) I have no idea if the parasitic draw is still there.

DasDream

You are right about that. I have both retainers on both sides of the engine. The retainers that run along side the spark plug tubes, and the retainers that sit on top of the ?timing belts? My spark plugs are all good because I have tested resistance on all of them and they are within the NGK specs. I'm not getting any spark to them because for some reason the ignition coils on both sides are not sending out spark. I tested 12v on both power wires to the electrical connection but I suspect that the ECU is in control of sending signal to the ignition coils. I have no idea what to diagnose now. My crankshaft positioning sensor is producing voltage and the wiring is good as far as I can tell

DasDream

That voltage gauge is a great idea! I'll check it out once I have more important stuff crossed off and can actually get my car running again HAHA. I was thinking about wiring one in somewhere sleek too. Have you heard of any easy way to test resistance and connection from the ecu to every sensor going to the engine? I was thinking about mapping out wire colors that go to the ECU plugs and confirming them with the sensors and wiring that run on those colors in the engine then check resistance from the ECU side of wiring to the engine side wiring and see if there is any broken wiring.

DVL5WRK95

ECU could need the capacitors replaced.

peterls

With such a high number of gremlins attacking your car all at once, I would start with the ECU. Find the exact P/N for it, and then buy a used one from E-bay. Open it, and see if caps look good or not (you can find a lot of info here and on the net about how to recognize bad capacitors, which is the main problem with our ECUs).
Then, if it looks good, install the new one and see if it makes any difference. It probably will.
As for shifting, it is usually the shift solenoid which is located in the A/T fluid pan, at the bottom of the car, not terribly difficult to access on 1st gen, probably easier than on the 2nd gen.