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1993 LS400 No spark/no start...Why I'm so confused...

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Old 07-18-13, 09:38 PM   #1
Jazzylexus
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Default 1993 LS400 No spark/no start...Why I'm so confused...

Help....before it went completely out, it wouldnt go over 65 without missing really bad, 1. it took along time to warm up after setting for any lengh of time 2. Heavy gas smell 3. No power 4. Missing bad 5. Low idle 6. sounds like exhaust is leaking 7. I want to run it off a cliff...but its my only transportation at this point, i've had 3 Machanics tell me all different things and have spent $670 on parts alone and $400 on machanics, all of whom are scratching their heads...i gave up it is sitting in my driveway, in the meantime my girlfriend is getting on my nerves because i'm having to use her car to take care of my business and her's, and we cant afford another car payment...What i have done is 1. replaced spark plugs/wires 2. fuel filter 3. ignition caps 4. Both rotors 5. ECU value 6. crank sensor 7. fuel pump is pumping fuel, 8. removed 2 convertors 9. had exhaust checked 10. and now i just give up...my last resort is to take it to the lexus dealership but i thought i would come here for help before i do that...please help me somebody... I use to love this car...now its like a bad relationship...at first everything is wonderful...then the bottom falls out... i still love the car...i just dont like it anymore...
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Last edited by Jazzylexus; 07-18-13 at 09:48 PM.. Reason: add line
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Old 07-18-13, 09:47 PM   #2
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I had the same problems and the same feelings, I was ready to shoot my car!

it turned out to be failing ECU capacitors - and the cool thing is, this one repair made ALL of those intermittent and confusing problems all go away at once!

PS - it turns out this is a very common problem on older LS400's, especially 92-97 models!
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Old 07-19-13, 11:37 AM   #3
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I would bet a doughnut that LScowboy is right. However, I think it might be useful to invest 5 minutes and a paperclip to see if any codes are present. It is quite easy - post here if you need instructions.
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Old 07-19-13, 12:16 PM   #4
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code reading instructions
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Old 07-19-13, 02:04 PM   #5
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You don't mention the ignition coils and the problem you have could also be down to one of them failing under load. The usual culprit is the passenger side one located on the engine block opposite the battery mounting tray.
If you run the car at night for a while check underneath to see if the cats are glowing generally a sign of a coil pack down so the engine is only running on 4 cylinders instead of 8.
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Old 07-19-13, 03:17 PM   #6
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Quote:
Originally Posted by steve2006 View Post
You don't mention the ignition coils and the problem you have could also be down to one of them failing under load. The usual culprit is the passenger side one located on the engine block opposite the battery mounting tray.
If you run the car at night for a while check underneath to see if the cats are glowing generally a sign of a coil pack down so the engine is only running on 4 cylinders instead of 8.
go to the 5:53 point in this video for an easy test of both coils, both igniters, and the associated wiring -
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Old 07-23-13, 09:10 PM   #7
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Quote:
Originally Posted by LScowboyLS View Post
I had the same problems and the same feelings, I was ready to shoot my car!

it turned out to be failing ECU capacitors - and the cool thing is, this one repair made ALL of those intermittent and confusing problems all go away at once!

PS - it turns out this is a very common problem on older LS400's, especially 92-97 models!
Thank you so much i will have it checked out, i will put new coils on it tomorrow, but have no idea of how to check the ecu capacitors...is there a shop that does that or who do you think i should have look at them? thank you so much
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Old 07-23-13, 09:13 PM   #8
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Quote:
Originally Posted by steve2006 View Post
You don't mention the ignition coils and the problem you have could also be down to one of them failing under load. The usual culprit is the passenger side one located on the engine block opposite the battery mounting tray.
If you run the car at night for a while check underneath to see if the cats are glowing generally a sign of a coil pack down so the engine is only running on 4 cylinders instead of 8.
thank you i had the converters removed at a machanics suggestion only to have the same problem he said they were glowing red... so i will change the coils tomorrow i found them at autozone for $48 each...i will post to see it that was what the problem was...thanks again guys...
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Old 07-23-13, 09:28 PM   #9
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Originally Posted by Gene01 View Post
I would bet a doughnut that LScowboy is right. However, I think it might be useful to invest 5 minutes and a paperclip to see if any codes are present. It is quite easy - post here if you need instructions.
Both mechanics i took it to said the car is not throwing any codes...so they started guessing at my expense how do you check it with a paperclip is it hard to do? how do you do it...please post instructions thank you...
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Old 07-23-13, 09:41 PM   #10
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Quote:
Originally Posted by steve2006 View Post
You don't mention the ignition coils and the problem you have could also be down to one of them failing under load. The usual culprit is the passenger side one located on the engine block opposite the battery mounting tray.
If you run the car at night for a while check underneath to see if the cats are glowing generally a sign of a coil pack down so the engine is only running on 4 cylinders instead of 8.
thank you so much, one of the guys at o'rielly told me thats what it sounded like to him as well,,, but the mechanic thought it was the crank sensor so i got that and still nothing, so tommorrow i will go get both coils and replace them and i will let you know if that was the problem...
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Old 07-23-13, 09:42 PM   #11
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Quote:
please post instructions thank you...
I posted the instructions in message #4 in this thread, scroll up and click the link!

Quote:
but the mechanic thought it was the crank sensor so i got that and still nothing
he is not much of a mechanic, no basis for that diagnosis with the symptoms you have

Quote:
i will change the coils tomorrow i found them at autozone for $48 each
there is no reason to do this, first of all, I posted a video of how to test them with a 10 cent T-pin and second of all, another reason not to replace them is that the Lexus coils are very well made and the Autozone coils are junk, there is no reason to replace expensive parts with cheap ones when that is likely not even the problem

quit listening guys at o'reilly and just buying parts and trying them, that will deplete all of your money you may need when you find the real problem! (and don't throw away that nice Nippon Denso crank sensor, put the Lexus parts back on, they are much better than your "new" ones you are buying at these silly auto parts stores )

here is the video of how to easily check the coils, igniters and their wiring again, go to the 5:53 point in the video to watch the test

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Old 06-25-14, 11:36 AM   #12
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Default Is ecu caps really my issue?

I have a 92 LS400. After about 15 minutes of running, it dies. Will not restart until it totally cools back down. I spray starting fluid in the intake and it fires off for a bit, so I am leaning toward the fuel pump. Anybody got any ideas? I took the ECU out and opened up, and everything not only looks really clean (no messes around the caps), but it just looks like a newer board than the ones in the Yamae pics. Plus, it was mounted to the back of the lower glovebox panel, not vertically like in the diagrams.
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Old 06-25-14, 12:22 PM   #13
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Quote:
Originally Posted by tfleetwood View Post
I have a 92 LS400. After about 15 minutes of running, it dies. Will not restart until it totally cools back down. I spray starting fluid in the intake and it fires off for a bit, so I am leaning toward the fuel pump. Anybody got any ideas? I took the ECU out and opened up, and everything not only looks really clean (no messes around the caps), but it just looks like a newer board than the ones in the Yamae pics. Plus, it was mounted to the back of the lower glovebox panel, not vertically like in the diagrams.
Hi,ECU caps may well not be your issue but they are well worth replacing ,even if only as a preventative measure . On the earlier cars the ECU is mounted to the back of the panel below the glovebox as you found ,I think the diagram you mention is for the 95/97 models .

You cannot tell if the capacitors are ok just by looking at them ,they may not be leaking but at that age are probably low in capacitance and not dealing with ripples very well.

After replacing mine the car was like new the improvement in engine smoothness and response was great ,shifts better as well .
I hope you get your problem sorted soon ,have you checked for any stored codes they may help to pinpoint the issue.
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Old 06-25-14, 07:04 PM   #14
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Quote:
Originally Posted by tfleetwood View Post
I have a 92 LS400. After about 15 minutes of running, it dies. Will not restart until it totally cools back down. I spray starting fluid in the intake and it fires off for a bit, so I am leaning toward the fuel pump. Anybody got any ideas? I took the ECU out and opened up, and everything not only looks really clean (no messes around the caps), but it just looks like a newer board than the ones in the Yamae pics. Plus, it was mounted to the back of the lower glovebox panel, not vertically like in the diagrams.
Hi,
While I cannot suggest anything useful about the engine running, aside from my suspicion that the FP is probably on its last legs (these things can lose life if you run low on gas which serves to keep it cool), I can say that I have a '92 and the mounting for your ECU is not unusual, since the one in my LS was similar.

Also, I took my ECU apart and even though the caps were not the Nichicon brand, since they were old (>18 years at the very least), I used the good advice from some very knowledgeable folk on here (think LSC & Yamae), and, purchased the specific caps suggested and did the replacement myself. It does make a pretty big difference, I can assure you!

Good Luck.
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Old 06-25-14, 08:32 PM   #15
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tfleetwood - since your symptoms are temperature-related, you might want to check your coolant temperature sender (the sensor for the ECU, not the one for the temp gauge).
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Old 06-25-14, 08:32 PM
 
 
 
 
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1993, 1996, 350, 400, crank, fuel, lexus, location, ls, ls400, sc430, sensor, spark, start, starting

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