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1994 ls400 with huge power loss...sometimes

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Old 12-26-12, 05:23 AM   #31
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once again...take it to a shop! do not let anyone here or any other forum diagnose ur car. i cant believe the mods here allow people to give such bogus advice,people are ripping apart or sending their ecu's off to be rebuilt when it may or may not be the problem..and here is another issue..its the people who do this for a living that are giving this advice..you're doing a dis-service to your profession and to the people on this forum
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Old 12-26-12, 08:37 AM   #32
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i cant believe the mods here allow people to give such bogus advice,people are ripping apart or sending their ecu's off to be rebuilt when it may or may not be the problem
ALL Lexus ECU's from the 1990's either now have or will have this capacitor problem, as has been explained on here before, by ECU design engineer Yamae, this is a known defect in the Nichicon PF(M) capacitor that was used by NipponDenso for more a decade starting in the late 80's.

So replacing the caps on your ECU is highly recommended, who wants to fight head-scratching drivability, starting, transmission, and A/C issues when the fix, if you do it yourself, is less than $10

We need to get back to a society where the men MAN UP and start fixing things, rather than throwing away money that could better help the poor on expensive repairs that are not that difficult if you have patience and attention to detail and a little MacGyver in ya!

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Old 12-26-12, 09:16 AM   #33
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lol yeah im all about fixing everything myself. im dedicating this weekend to the car, i have the service manuals and all and will hopefully figure it all out.
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Old 12-26-12, 01:22 PM   #34
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the ECU may be the problem, but should merely be a step in the diagnosis process, not a universal end-all. OP if you've eliminated every other single possibility (ie checked through the entire ignition, fuel, timing, and intake systems) then looking at the ECU again would make sense. If you haven't, well, you know where to start.
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Old 12-27-12, 04:03 AM   #35
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thank you!
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Old 12-27-12, 01:27 PM   #36
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if you've eliminated every other single possibility (ie checked through the entire ignition, fuel, timing, and intake systems) then looking at the ECU again would make sense. If you haven't, well, you know where to start.
I think the point being missed here, it that a malfunctioning ECU can throw off the standard troubleshooting process, in the mildest form by not throwing codes or even communication with a scanner properly, all the way to giving misinformation in the troubleshooting process (a malfunctioning ECU can give the appearance of a lot of other stuff, and your standard measurements will be thrown off, causing someone to end up replacing parts that appear to be defective, when they really aren't!)

On modern cars, the LS400 being one of them, proper correct diagnosis of drivability, transmission, and many other problems depends on a properly functioning ECU.
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Old 12-27-12, 02:49 PM   #37
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Quote:
Originally Posted by LScowboyLS View Post
I think the point being missed here, it that a malfunctioning ECU can throw off the standard troubleshooting process, in the mildest form by not throwing codes or even communication with a scanner properly, all the way to giving misinformation in the troubleshooting process (a malfunctioning ECU can give the appearance of a lot of other stuff, and your standard measurements will be thrown off, causing someone to end up replacing parts that appear to be defective, when they really aren't!)

On modern cars, the LS400 being one of them, proper correct diagnosis of drivability, transmission, and many other problems depends on a properly functioning ECU.
I didn't miss anything. The ecu is like cereal, PART of a balanced breakfast, not all of it.

You could have a factory fresh ECU and it would be completely worthless if the 20year old ignition system needs new wires/plugs/rotors/caps or similarly aged injectors are clogged/sticking or etc... The likelyhood of basic maint. having been ignored in the past causing such issues is exponentially higher than a leaking cap causing problems.

I maintain, first step towards fixing any drivability issues is making sure that maintenance is current BEFORE looking for any single broken part. (ECU included.)
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Old 12-27-12, 03:36 PM   #38
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if the begining of the thread was read it says ALL maint items have been replaced over the last 6 months (coils, rotors, dist caps, wires, plugs, O2 sensors, fuel filter, injectors cleaned, VAF replaced, etc...)
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Old 12-27-12, 04:13 PM   #39
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the AFM is part of the EFI system and wasn't mentioned...
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Old 12-27-12, 04:25 PM   #40
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we arent the ones missing the point here..every problem that comes up u revert to the ecu caps as being the culprit.
to the op u have replaced caps and also purchased a rebuilt ecu..u have thrown parts at this car and all u had to do was send it to a reputible shop and have it diagnosed properly..and yes there are many shops who can diag a pre obd2 car!
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Old 12-27-12, 04:46 PM   #41
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After reading this, I'm glad the Celica has a carburetor.
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Old 12-27-12, 04:58 PM   #42
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the 1970 Celica GT 1600 is a great car! - if it was just a little safer!!

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Old 01-20-13, 12:59 PM   #43
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ok so in an attempt to test my throttle position sensor... i got no reading between vta and e2 at the ecu plugs.. so i test vta and vc and get the constant i expected... so i test the resistance between e2 at the ecu and e2 at the tps connector and i get 2100 OHMS but i get 0 ohms at e2 on the afm/vaf/maf whatever its called on this car... so theres something up between the splice (or at the splice) between the ecu and the tps/afm... now if i can just figure out where its spliced at...
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Old 01-20-13, 05:41 PM   #44
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its all wired up, checked grounds between the tps, vaf, and the temp sensors and all is well (they use the same sensor ground) and all is well.. adjusted the TPS(it was off by about 10*) and it has a 600ohm resistance at idle, where its supposed to be .5-6ohms.. also on a sweep it has spots that the resistance stays flat, and others where it seems to go lower, even though i ws moving it smoothly from 0-100% so it seems the tps needs to be replaced.

on another note, opened up the used ecu i bought, and it has been "repaired" but using some cheap looking caps (Illinois capacitors) BUT the board it self is in much better shape. so i went ahead and installed the old ecu with the correct type caps in.

the car feels better, but it usually goes a while before it feels funny again
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Old 01-20-13, 07:23 PM   #45
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make sure the TPS you buy is manufactured by NipponDenso or Aisin - other TPS's are not Toyota OEM and not so hot.
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Old 01-20-13, 07:23 PM
 
 
 
 
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1994, 400, 91, ecu, fix, intermittant, lack, lexus, loss, ls, ls400, power, power loss, video, youtube

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