86elco

Trying to get some guidance, opinions, or someone to point out the one small thing I'm overlooking. I bought this Celsior back in early August and started having an intermittent power loss issue around the second week of owning it. The issue has progressed from being once or twice a week to now basically every time I drive it. When this issue occurs the car becomes way down on power. A soft take off from a stop sign that I would normally use 1/4 or less throttle for will need 1/2 or more to accelerate at the same pace. During this the car feels suffocated and just overall not right. The gear changes can also feel delayed or harsh when this is occurring. This can start happening at any time whether the car is cold / hot / been driving fine for an hour. One day it might do it every single drive the next it may not occur at all. There are no warning lights on and nothing obvious that stands out the techstream live data.

At this point I have basically done everything I can think of. The first thing I checked was the ECU even though that does not seem to be as common with the VVTI setups. I saw no issues with it but sent it out to be checked anyways. Capacitors were replaced along with a driver but I never got any info on if anything was actually wrong. Everything on the engine has either been tested, observed with a scope, or replaced. Every wire has been tested from sensor back to the ECU. The transmission, torque converter, can flex plate were also just replaced with another setup from an importer. Nothing has made any difference with this issue. Currently I am waiting on another Celsior ECU to arrive and have already pulled the immobilizer bin from the one in the car to write to the replacement. I have always suspected the ECU as the main culprit but have avoided it due to the immobilizer deal. It was also replaced with a Denso unit while still in japan sometime around 2007. This is likely going to be my last attempt with this car unless I can come up with something else to check, With the cost of the car and the parts / time put into it I am way upside down in this thing and will either part it out or sell it as a roller.

Some background on the car that I have found through paperwork. Car appears to be one owner prior to me. Sold at Yamaguchi Toyopet in 97 and stayed in that area getting all services done by that dealer until it went up for auction in 2023. Total Km as of now is 127,000. The car only had 2700km put on it from 10/2020 until it was sold in 3/2023. I don't know if it was not being driven and then sold because of this issue or if sitting for so long played a part in whatever has developed.

Tallyhoe

I was going to suggest the Performance D solenoid on the transmission... My 07 Tundra was doing similar things where it needed more throttle to move forward. I doubt the ECU will give you a code for it, but checking the transmission fluid level and filling it as necessary... or replacing all the fluid in there... not the flush that will probably create a bigger headache for you.

400fanboy

"I replaced the ECU" by a previous owner is... well. Trust, but verify.

How did you test the ECU? Did you do this?

https://www.clublexus.com/forums/ls-...-by-yamae.html

Visual inspection is *not* sufficient unless you know specific name brands\model numbers of capacitors.

86elco

The transmission and torque converter have both been replaced and the issue stayed the same. The unit was replaced due to a shop botching a torque converter install and damaging the input shaft on the trans.

The ECU was 100% replaced in the past. There is a shop invoice for the replacement from 2007 and the ecu is labeled as a Denso replacement unit. There is no documentation for why it was replaced. just cost of the install and the ECU itself with matching serial numbers.
The test posted by Yamae along with a very in depth visual check (digital microscope with lighting) was performed by me. The testing showed no issues and the board looked immaculate. However, I am not an expert in auto ECUs so I sent the unit out to a highly recommended person to have it checked. This was really just a waste of time / money as there testing was to just slap capacitors in it along with a "driver", scribble on the case, and charge me almost $500. Either way this had no effect on the issue.

Tallyhoe

Sorry have a lot on my mind and I may have lost my train of thought and posted an incoherent reply....
My suggestion above was due to the shifting issue, when I re-read all your post, then it doesn't really apply, since the transmission was replaced, then again these are pretty old transmissions and may still have the initial issue with slipping like others have complained about, you never know with salvaged transmissions, and most shops will pull out a salvage yard/junkyard transmission and swap it as if it were new but may have the same issue as yours. I would look up salvage yards and pull valve bodies, or solenoids out of them and test them out on yours. Don't have much to lose since it's already slipping.

I'm unfamiliar with foreign country vehicle equipment, but does it have catalytic converters? Maybe those are getting clogged up. My SC400/ Soarer would get all weird when I was misfiring and would accelerate, but very delayed. More like a surge acceleration where it would need full throttle for it just to start idling forward, but then it would catch like nothing and take off. If this is sort of the case, then I would also look at ignitors if you have any.

Losiracer2

how is your catalytic converters? are they operating as they should and not clogged?

86elco

Cats are good based on pressure test. It was at or less than 1psi pre and post cat from idle to 2500ish rpm on both banks. All O2s are new Delphi units and live data looks good for sensor readings.

Got the new ECU in today. From warranty stickers it has been opened up before by Module Repair Pro. There is a couple of paint dots on a few chips, but everything looks oem. Not really sure what they did with it if anything. Hopefully its not a dud out the gate. I was able to read the IC900 chip and wright my original BIN to it so fingers crossed it passes the key security when I try it out tomorrow.

86elco

Update:
Got the new ECU installed today. Luckily the security light went out as soon as I inserted the key so the BIN swap was a success. Started up fine and proceeded to test drive it for around 45 minutes. Mix of city / highway / city. Everything was good up until I was almost home. Decided to make a few more sets of turns through a downtown area. Took off from a stop sign and thought I felt the power dip out but returned to normal. Thought maybe I was hyper focusing on everything and picked up on nothing. One street over taking off from the next stop sign, power loss in full force again. However, this time I heard the warning chime and got an notice on the dash for engine system. Sucked the issue returned but never have I been so happy to see a check engine light. Pulled the code and got P0325 knock sensor 1 Circuit.


I replaced both sensors towards the start of this issue after the ECU repair did not change anything. I used NTK sensors but was not able to source a harness in a decent time frame. I checked the entire harness visually and with a meter and didn't see any issues. Maybe I overlooked something there or its an issue in the connector at the rear of manifold or main harness. Going to try temporarily jumping the signal from sensor 2 onto sensor 1 at the ECU and see if the issue clears for a few day before I commit to re pulling the intake manifold off.

Tallyhoe

When you say power dip, do you mean your engine dies?

I watch my tach when I release the gas pedal and make a mental note of how far that needle drops. Like previously stated I have a 93 SC400 and I could tell when my engine might die. My normal needle drop is about 100 rpm or the needle barely drops down. If my needle drops say 400rpm and that's a big drop, a noticeable one, I start to get comfortable in my seat and start using both feet. Holding the brake at a full stop and holding the gas slightly just to keep it at idle speed almost like a manual. This took me a little bit to master, but I found a comfortable position and I rarely do it now, but I do keep that in mind as my issues are coming back again. Your advantage is that you could pull codes and see what might be going on. I would suggest replacing that knock sensor with a Denso one, it may be more expensive but may resolve all your issues for a longer period of time.

BNastee

You should live-monitor the timing when you feel that dip in power. I bet its pulling the timing way back when you feel that.

1. I've done the jumper trick on my 2000 Lexus. I'll fix it correctly someday.

2. On the 1999 I have my trials are documented in the chronic spark knock thread. I think Yamae's suggestion of Techron has helped. Different sensors, wiring confirmation, etc have not helped.

Yamae

In case when you need to replace the wiring loom, the part was discontinued and you need to make a home made loom using a special coaxial cable which withstand high temperature such as the RG 316 U with a connector. The coaxial cable is available at Mouser or Digikey.

86elco

The power loss I'm getting is more of an overall reduction than a sudden shut down like the engine dying or the drive by wire dropping out.

It is definitely pulling timing when this issue was occurring. That was what led me to replace the knock sensors initially. I did find it strange that whatever was going on was bad enough to be that noticeable but not throw any type of warning. With the old ECU never throwing the code I got with the new one I figured that I guessed wrong and moved onto the next idea. The intermittent part is where it really got me as every time I hooked my scope to the knock sensors I had a really good signal on both sensors.

I will definitely be grabbing some of this for the future repair.

Another Update:
Probed both sensors from the knock sensor plug behind the manifold to the ECU pins. Good signal between both which I have checked before. Whatever is going wrong must be in the harness where it ties into the starter area or feeds back into the main harness. Either way I cant see it visibly and I cant catch whatever is going on with a meter when I am able to probe it. Ended up doing the bypass at the ECU by tying both sensor inputs to the signal from knock sensor 2. I drove around for nearly 2 hours and put around 100 miles on the car without the issue coming back. This is more than I have been able to drive it in the last 4 months combined. If it can do this for a week straight I will call it fixed and plan out re-pulling the intake manifold and figuring out building a new knock sensor harness.

Findings so far - No codes from original ECU. ECU checked and capacitors replaced, still same issue with no change. Replaced ECU with one from another Celsior. Issue returned but showed a check engine light with P0325. Jumped wires at ECU and issue has yet to come back.
So something wrong with the original ecu not related to capacitors and intermittent signal loss from knock sensor 1.

86elco

If anyone has any interest in seeing it, this is my work through list for this issue. Excel file with multiple tabs so hopefully settings it as an attachment wont break it or make it a jumbled mess.

dveneman

I must commend you on your thoughtful analysis, patience and determination.
I think I would have lost it during the transmission debacle.

86elco

I had given up on it after getting it back from the transmission repair and actually had it listed for sale in various places. Got on ebay browsing and the ecu I bought popped up as suggested for $75. Said what's another $100 at it for a last attempt and here we are lol. Sucks that all the issue appears to be from a wire that took 5 minutes to bypass. Just had no real way of seeing it until changing out the ecu.

Update:
I am calling it fixed. I have stress tested the car as much as possible over the last 4 days. Last night, I loaded the car down with 4 people and put another 200 miles on it. Car did not give a single issue throughout the mix of highway and city driving. Filled it up this morning and calculated it around 25mpg since the fix. That's much better than the 12-13 mpg I was getting when the issue was present. I ordered up the wire Yamae posted and the connectors / terminals for the knock sensor. I will work out getting the harness made and installed later. For now I am going to enjoy the car for a while and install this set of fortune auto coils that have been sitting in the box for 4 months.

Since I haven't done so yet here is an obligatory pic of the car after a fresh wash -