I just did this on my SC400 and it made a huge difference in throttle response and power. Where is the best place to source a new fuel pump ECU?

 

https://youtu.be/GN_NDJxWA58
I've been reading through here, I can't quite find what relates to my issue so forgive me if I am on the wrong thread, have had this problem since I bought the car. Seems that anything over 2k rpm the car won't hold it, as you hear in the video that I've linked. I'm stumped, the car will start, idle just fine, drive fine but anything over 2k and up the throttle just surges. Again sorry if I'm in the wrong place. It is throwing codes for the iat and maf, they've been cleaned and seem to be working fine.

 

I have the same issue with mine right now what you may want to try is check ur ecu its under passenger side kick well carpet and the ecus are known to have capacitor leakage issues and that will cause the issue also get ur CEL light checked if there is one a way to make sure ur ecu works is put ur key at the on position and u should see a CEL light if you dont you have an ecu issue hope this helps

 

Thanks man, turns out I'm just dumb and my tps needed adjustment. I thought I had done it. Along with my maf failing and alternator. All is good now except the car stalls when I honk the horn -__-

 

This is a legacy thread that keeps paying dividends. Im new to the set and purchased of a "92" SC400 that neded TLC. My mechanic went ape sh*#* trying to get consistent and smooth excelelartion without delays and bog downs. I was convinced that The ECU was bad but he disagreed after testing. A full tune up was done with coils, wires, plugs and filters. Lastly discovering leaking injector seals. after replacement and cleaning the problem persist.
This issue apparently had been addressed before by prior owner and cutting and moving wires to bypass components was his apparent remedy...you guessed it, that didn't help at all. My lovable indie put everything back to factory and finally nailed the problem by replacing the ECU (Computer) and bang the culprit stuck its ugly head out when he replaced the CO Oxygen Sensor. An entire week of testing diagnostics and temporary part replacements paid off.
Cost????? $814.00
In closing I have to say that this thread helped tremendously to help eliminate possibilities and saved me a mint Im sure. After I gave my indie a copy of your post he seemed to be a heck of a lot more confident and resolved the problem within 24 hours.She burns rubber now with boundless power and appears to be thanking me like a she been cured of a VD. XOXO to all yuse gizes!!!

 

Hillarious!!!

 

Bump for a good read to those with similar issues

 

Since its been getting very cold at night here in L.A. (in the 40s), my car has been stuttering on idle every morning. It disappears once the motor is up to normal operating temps. I found this thread and decided to check the air meter and TPS. I checked the THA-E2 terminal on the air meter and it's within specs. I back probed the air meter, blue/red wire showed 4.97 volts with the key ON. Also both brown wires showed 0.00 volts. Is this acceptable or is it time for a new MAF? I started the car and yellow/green wire showed 2.48 volts with the engine running.

Also which screw below is for adjusting the throttle stop?

 

The screw thats by itself with the yellow paint on it, Looks like your allen screws are factory plugged. Its better to find the real idle prob. and not adjust the idle stop screw.

 

if they are the original fuel pump i would of just replaced it, even the fuel filter while your in there, cheap insurence.

 

I got a nice 92 SC400 from my Dad (RIP) that has full maintenance records. 177k miles but had timing belt done, coils replaced, starter, alternator, even the PS was serviced. so it runs as smooth as a sewing machine, has great throttle response and drives like new...BUT it has a annoying flat spot right off idle. If I baby the throttle I get no hesitation, just a smooth take off. If I use the throttle as a normal person, I get a hiccup right off idle for about 1/8 of a second. Its like the trans is downshifting or something (in D) once I get past the hiccup, a surge of power hits and its off to the races. I cleaned tons of carbon out of the EGR and throttle body (took it off and cleaned it thoroughly) but didnt disturb any factory calibrations on any of the painted screws. I had a pretty good ridge of gunk on the plate and where they meet but it is smooth and clean now. Still have the issue, Im thinking maybe TPS or trans speed sensor? When it gets hot the trans seems to shift hard from 1-2 on light throttle and the O/D seems to also kick in (does the O/D run in all gears?) when I turn off the O/D it seems a little less 'busy' when I take off. My old LS400 was butter smooth with about the same mileage. I did look at the ABS/TRAC ECU last week and it looked good as new when I opened it. No dust, no cap leak, assembly line clean. I may look at the ECU next week when I have some vacation time as this is my DD until I can get my old carbed B2000 smogged (another long story).

 

Also about the vacuum hoses: what should be a factory vacuum reading at hot idle? I had a few hoses break on my when I was taking off the TB (PITA that one big hose under it) so Im sure the others are as brittle. My MAF duct hose to TB had a small tear in it but I siliconed it and taped it so I believe its airtight now.

 

my sc 400 will not accelerate properly sometimes ...at 30 or 40 mph when press gas pedal all the way car will increase rpm but no power for few seconds...any ideas?thx a lot guys.

 

Hello, CL Friends
Recently my car(93 SC400) started rough idle, around 100-400 rpm... sometimes drops to 100, sometimes to 400.
Runs good, but on lowered RPM while A/C is turned OFF, as i turn on a/c the car starts to shake very often at stops in any gear. be it D/N/R... in reverse it feels like the car is jumping backwards....
We've recently cleaned TB, ISC Valve(also checked for proper work-ability by applying battery voltage in order described by factory manual), EGR, Replaced PCV valve, timing is done, water pump, cables, plugs, oil change, water temp to ECU sensor replace, water temp to gauge sensor replaced, TPS replaced and re-calibrated by the book with all parameters aligned well in spec range.
I don't know what to think next...
Nothing stopped the car from shaking.
The code i get is 21 (left bank main o2 sensor).
We are trying hard to solve the problem.
---

• The rpm drop can be anytime anywhere (independent of AC)
• Turning AC ON does not increases RPM, rather drops RPM even more.
• The shaking begins when A/C is turned ON. The shaking is of type like when you turn on the A/C so the car shakes one or twice, but here it is continuosly occurs...

Any help is well appreciated!

Thank You in advance.

 

Savais sickly at this point we have driven my car back from Florida Approximately about brew 500 miles give or take dry fine get to Georgia stop the car get up go to the card in the morning no Crank. At 1st I thought it was the fuel filter replace the part of course it is not it is the ICU even though the test did not do anything whatsoever. So at this point not having the funds be decide to bypass the ECU. That's all fine and dandy works well enter minutely sometimes we even hook backup the ECU and around a little better than goes back down. Then oil pressure light comes on which I being very naive and knowing nothing about lights or Lexus's myself didn't quite understand what it meant and thought it meant cool it checked it it was fine. However the car begins to overheat runs to read one time when chatted crank at a later time no crank whatsoever and there's now water emitting from underneath the engine. Can these 2 issues be related. The car ran perfectly fine other than needing new bushings. Any Ideas , suggests or related issues would be greatly appreciated. The vat has now been sitting for over a month. With no funds to have diagnostic done at shop sigheatikms appreciated so we a th least know where to start