Holy goabs of torque batman!!!! And less pinging too!!!!
01-09-09, 08:07 AM
#121
Lexus Champion
Hello guys, I didn't manage to read all the 8 pages so I'm going to chime in on what might have happened. Most of us don't know that our cars have a torque limiter that normally kicks in when we shift from P > R and from N > D. This limiter is computer controlled and retards the engine quite substancially for the engagement process. This is why most of our transmissions seems so smooth even when changing gears and all that.
Recently mine went out the window and the torque limiter program or whatever failed to kick in at the right times, meaning they were delays which you could feel. What happened to me is when shifting from N > D I would get a very slight "engagement shudder" that told me the car was ingear and ready. However when gassing it the engine had all but no torque at all. Felt like driving off in 2nd or 3rd. After about 3 seconds I would get another shudder and this time it was the torque limiter turning off, it stayed on way too long causing the feeling of "no power".
When I turned to the mechanic I thought that the gears were actually engaging 2nd first then later deciding to go into 1st but diagnostics determined that it was actually the ECU or more specifically the Transmission ECU (apparently LS400s have many ECUs). I got the problem fixed and now I don't even feel a shudder in the transmission at all. My mechanic who happens to be good with electronics said that some of the resistors were shot and melted some of the protective coverings causing a slight shot which kept the torque limiter on for far too long.
I suspect that you might be having this same problem but this time your torque limiter is on permanently. Why don't you go down to the local wreckers and borrow a Trans ECU and plug it in yours to see if there is a difference. I didn't poke around so I dun know where the Trans ECU is but my mechanic said that you just need to trace the ECT switch and you got it.
Recently mine went out the window and the torque limiter program or whatever failed to kick in at the right times, meaning they were delays which you could feel. What happened to me is when shifting from N > D I would get a very slight "engagement shudder" that told me the car was ingear and ready. However when gassing it the engine had all but no torque at all. Felt like driving off in 2nd or 3rd. After about 3 seconds I would get another shudder and this time it was the torque limiter turning off, it stayed on way too long causing the feeling of "no power".
When I turned to the mechanic I thought that the gears were actually engaging 2nd first then later deciding to go into 1st but diagnostics determined that it was actually the ECU or more specifically the Transmission ECU (apparently LS400s have many ECUs). I got the problem fixed and now I don't even feel a shudder in the transmission at all. My mechanic who happens to be good with electronics said that some of the resistors were shot and melted some of the protective coverings causing a slight shot which kept the torque limiter on for far too long.
I suspect that you might be having this same problem but this time your torque limiter is on permanently. Why don't you go down to the local wreckers and borrow a Trans ECU and plug it in yours to see if there is a difference. I didn't poke around so I dun know where the Trans ECU is but my mechanic said that you just need to trace the ECT switch and you got it.
Is this a GREAT site or what? After 8 pages and 114 posts and trying virtually everything to resolve a mystery problem... here a guy jumps in with his THIRD post and presents a viable if not probable solution!!!
Many mechanics have faced mystery problems. All makes and models will have them if there are enough cars built. Some could be flood damaged cars or freak electrical surge (lightning, welding or other) that create diabolically irritating intermittent failures...
I hope that Och or someone else with this problem will fix their car and report back.
01-10-09, 09:14 AM
#123
Trans ECU is a part of main ECU, at least in the first gens. I had that rebuilt, thats not my problem. I just dont even drive the car anymore, its sitting in my driveway, i have the Apexi SAFC Neo piggyback sitting on my desk since last fall, havent had the time to install it.
01-10-09, 09:17 AM
#124
By the way, whatever issues that I had with my GS were solved when I did the tuneup - cleaned tb, replaced spark plugs, pcv valve, ect sensor. I still gotta do the waterpump/tb/o2 sensors, I have the parts sitting here, but I haven't had the time to do it.
01-10-09, 09:28 AM
#125
i love this website and i appreciate everyone's enthusiasm about their LS. i hope no one takes offense to this, but that being said...
1) you can't blame Lexus for not looking to spend too much money at Lexus headquarters in R&D trying to find out why a 15 year old car doesn't run as smoothly as it did 15 years ago (i think it has something to do with the 15 years), and
1) you can't blame Lexus for not looking to spend too much money at Lexus headquarters in R&D trying to find out why a 15 year old car doesn't run as smoothly as it did 15 years ago (i think it has something to do with the 15 years), and
Lets take the luminuos gauge cluster for example. When Lexus first debuted they made a lot of hype and fuss how they are the first ones to ever produce a luminous cluster, etc. But the fact is, that cluster develops a range of problems on all of first gen Lexus cars - both my LS and GS had faulty cluster, people with ES and SC have the same troubles. Lexus never recalled it, and has the nerve to charge people $1800+ for a rebuilt piece of junk thats going to fail in a few years again. Lexus is well aware of these common problems, and they are mostly fixed on the 2nd gen models, but it does leave 1st gen owners sore.
2) if you're trying to turn a decade and a half old luxury auto into a race car, you're going to be unhappy with the end result. sure you can squeeze some HP out here or there, or you can throw a custom turbo and exhaust in it like some on the board have done, but have realistic expectations.
01-14-09, 11:36 AM
#126
Driver School Candidate
Join Date: May 2008
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Och, when you replace the ECU, what is involved in getting to it? I have read on the site that you can see the part number from under the glove box when you remove the lower panel. I have try this and can only see the edge of it that plugs in. Any info would be helpful. Thanks
01-15-09, 03:49 AM
#127
Och, when you replace the ECU, what is involved in getting to it? I have read on the site that you can see the part number from under the glove box when you remove the lower panel. I have try this and can only see the edge of it that plugs in. Any info would be helpful. Thanks
With that being said, its not really a PITA, just a bunch of screws.
01-16-09, 04:53 PM
#128
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Thanks I see what you mean. Now do you know of a good place to find a used ecm. I have looked on ebay and nobody has my part number, which is 89661-50141. Is any of the other numbers compatible? Thanks will all the help
06-15-09, 02:23 AM
#129
Hello guys, I didn't manage to read all the 8 pages so I'm going to chime in on what might have happened. Most of us don't know that our cars have a torque limiter that normally kicks in when we shift from P > R and from N > D. This limiter is computer controlled and retards the engine quite substancially for the engagement process. This is why most of our transmissions seems so smooth even when changing gears and all that.
Recently mine went out the window and the torque limiter program or whatever failed to kick in at the right times, meaning they were delays which you could feel. What happened to me is when shifting from N > D I would get a very slight "engagement shudder" that told me the car was ingear and ready. However when gassing it the engine had all but no torque at all. Felt like driving off in 2nd or 3rd. After about 3 seconds I would get another shudder and this time it was the torque limiter turning off, it stayed on way too long causing the feeling of "no power".
When I turned to the mechanic I thought that the gears were actually engaging 2nd first then later deciding to go into 1st but diagnostics determined that it was actually the ECU or more specifically the Transmission ECU (apparently LS400s have many ECUs). I got the problem fixed and now I don't even feel a shudder in the transmission at all. My mechanic who happens to be good with electronics said that some of the resistors were shot and melted some of the protective coverings causing a slight shot which kept the torque limiter on for far too long.
I suspect that you might be having this same problem but this time your torque limiter is on permanently. Why don't you go down to the local wreckers and borrow a Trans ECU and plug it in yours to see if there is a difference. I didn't poke around so I dun know where the Trans ECU is but my mechanic said that you just need to trace the ECT switch and you got it.
Recently mine went out the window and the torque limiter program or whatever failed to kick in at the right times, meaning they were delays which you could feel. What happened to me is when shifting from N > D I would get a very slight "engagement shudder" that told me the car was ingear and ready. However when gassing it the engine had all but no torque at all. Felt like driving off in 2nd or 3rd. After about 3 seconds I would get another shudder and this time it was the torque limiter turning off, it stayed on way too long causing the feeling of "no power".
When I turned to the mechanic I thought that the gears were actually engaging 2nd first then later deciding to go into 1st but diagnostics determined that it was actually the ECU or more specifically the Transmission ECU (apparently LS400s have many ECUs). I got the problem fixed and now I don't even feel a shudder in the transmission at all. My mechanic who happens to be good with electronics said that some of the resistors were shot and melted some of the protective coverings causing a slight shot which kept the torque limiter on for far too long.
I suspect that you might be having this same problem but this time your torque limiter is on permanently. Why don't you go down to the local wreckers and borrow a Trans ECU and plug it in yours to see if there is a difference. I didn't poke around so I dun know where the Trans ECU is but my mechanic said that you just need to trace the ECT switch and you got it.
Has anyone experiencing these problems ever replaced the fuel pressure regulator?
My reason for suspecting this part;
My 95 seems a bit down on torque from a standstill, i always just put it down to being a big heavy car and a 'peaky' quadcam engine, it still gets up and goes great when i want to overtake etc. I'd say the peak power output is just where it was from the factory, but its lacking lower in the rev range.
Like someone else mentioned, the car lags/bogs from a standstill till around 3500rpm if i stomp it to the floor, but if i'm already doing 5-10km/h (throttle partly open) and plant the boot it takes off like a rocket, with good usable torque well below 3500rpm.
When the car is idling, throttle shut, the fuel pressure reg is in full vacuum, holding the reg hard closed. When you stomp the gas, the instant vacuum change should open the reg instantly to increase the fuel pressure. If the FPR actuator/diaphragm is slow to react (possibly clogged with carbon/oil etc), the engine will run lean (15-20psi under the ecu's expected fuel pressure the maps were written for) until either the fuel pressure comes up or the ecu injects enough fuel to compensate - which it would if it was running no MAF (rich in limp mode).
If the FPR was jamming closed with the throttle shut, it could definitely respond differently with part throttle up to 10km/h, then jumping on the gas.
I think its fairly safe to assume that my UCF20's MAF is fine (different MAF to UCF10/11), and most likely the ecu also, i do have to replace my fuel filter (next week) but otherwise my car is is great shape, done 190,000kms.
What do you guys reckon?
Gene
Last edited by gmacrae; 06-15-09 at 01:35 PM.
06-15-09, 08:27 AM
#130
I'm familliar with the feeling of this torque limiter engaging/disengaging (when i shift from D to R to back down my driveway i feel the gear engage, then about a second later the torque limiter disengage. Its definitely an original idea but im sure you would notice if it were engaging too much or too often during a power run 0-60mph.
Has anyone experiencing these problems ever replaced the fuel pressure regulator?
My reason for suspecting this part;
My 95 seems a bit down on torque from a standstill, i always just put it down to being a big heavy car and a 'peaky' quadcam engine, it still gets up and goes great when i want to overtake etc. I'd say the peak power output is just where it was from the factory, but its lacking lower in the rev range.
Like someone else mentioned, the car lags/bogs from a standstill till around 3500rpm if i stomp it to the floor, but if i'm already doing 5-10km/h (throttle partly open) and plant the boot it takes off like a rocket, with good usable torque well below 3500rpm.
When the car is idling, throttle shut, the fuel pressure reg is in full vacuum, holding the reg hard closed. When you stomp the gas, the instant vacuum should open the reg instantly to increase the fuel pressure. If the FPR actuator/diaphragm is slow to react (possibly clogged with carbon/oil etc), the engine will run lean (15-20psi under the ecu's expected fuel pressure the maps were written for) until either the fuel pressure comes up or the ecu injects enough fuel to compensate - which it would if it was running no MAF (rich in limp mode).
If the FPR was jamming closed with the throttle shut, it could definitely respond differently with part throttle up to 10km/h, then jumping on the gas.
I think its fairly safe to assume that my UCF20's MAF is fine (different MAF to UCF10/11), and most likely the ecu also, i do have to replace my fuel filter (next week) but otherwise my car is is great shape, done 190,000kms.
What do you guys reckon?
Gene
Has anyone experiencing these problems ever replaced the fuel pressure regulator?
My reason for suspecting this part;
My 95 seems a bit down on torque from a standstill, i always just put it down to being a big heavy car and a 'peaky' quadcam engine, it still gets up and goes great when i want to overtake etc. I'd say the peak power output is just where it was from the factory, but its lacking lower in the rev range.
Like someone else mentioned, the car lags/bogs from a standstill till around 3500rpm if i stomp it to the floor, but if i'm already doing 5-10km/h (throttle partly open) and plant the boot it takes off like a rocket, with good usable torque well below 3500rpm.
When the car is idling, throttle shut, the fuel pressure reg is in full vacuum, holding the reg hard closed. When you stomp the gas, the instant vacuum should open the reg instantly to increase the fuel pressure. If the FPR actuator/diaphragm is slow to react (possibly clogged with carbon/oil etc), the engine will run lean (15-20psi under the ecu's expected fuel pressure the maps were written for) until either the fuel pressure comes up or the ecu injects enough fuel to compensate - which it would if it was running no MAF (rich in limp mode).
If the FPR was jamming closed with the throttle shut, it could definitely respond differently with part throttle up to 10km/h, then jumping on the gas.
I think its fairly safe to assume that my UCF20's MAF is fine (different MAF to UCF10/11), and most likely the ecu also, i do have to replace my fuel filter (next week) but otherwise my car is is great shape, done 190,000kms.
What do you guys reckon?
Gene
06-16-09, 12:59 AM
#131
lol, just priced a new FPR from toyota, roughly $600NZ ($350US)... but if i were to replace it i'd probably use an adjustable aftermarket one anyway (not rising rate, just 1:1). Once i've done my fuel filter, this will be my next project i think... will get back to you all with the results 
06-16-09, 05:31 AM
#132
It could be, but I doubt it because the car runs well when cold and suddenly torque drops once the motor is warm. But who knows, if u do replace the FPR, let us know how that works.
BTW, I installed the SAFC Neo, its crap, only makes things worse.
BTW, I installed the SAFC Neo, its crap, only makes things worse.
06-16-09, 03:01 PM
#133
Do these motors have fuel pulsation dampners? I remember removing it from my supra thinking it was just another thing that could go wrong, thats another possibility perhaps.
06-16-09, 05:16 PM
#134
Och: Did you try increasing and decreasing fuel thru the rev range with the SAFC? Were you able to work out if the engine needs more or less fuel to help sort the problem?
06-16-09, 06:05 PM
#135
Regardless I think the root of the problem is A/F ratio, and I dont know whats causing it, but to make matters worse I believe the ECU retards ignition when it hears knocking, so its trying to cure the problem with the wrong medicine and only makes things worse.
I'm thinking about buying an aftermarket ECU (adaptronic) and tuning the car with that.
Another thing I might try disconnecting knock sensors and see what that does.