Jump to content
robertcope

1999 Lexus SC400 - I messed up good this time

Recommended Posts

My last outing, I had disabled the ABS because after the outing before that, when I got home, the ABS pump was running constantly when the ignition was off. The car was not very drivable without ABS; the rears locked up very easily, and in fact, I ruined a nice set of tires while making a lot of smoke! I put the car up on my lift and began trying to figure out what was going on.

 

It took me far too long to sort it out, but eventually I found the problem:

 

5c298a8897ec7_IMG_20181230_160718.jpg

 

5c298a94d01d4_IMG_20181230_161559.jpg

 

5c298aa2da410_IMG_20181230_161833.jpg

 

On the plus side, I have a very good idea how Toyota writes services manuals, electrical diagrams, etc now. And the damage isn't _that_ bad. Wiring is definitely not an area of expertise for me, but I think with a little patience I can fix this up.

Share this post


Link to post

Before I got the Datsun I feared and loathed wiring. After the Dastun, I find it puts my in a zen state of complete focus. I now really enjoy the tedium of it in some odd way. (I also took a class on electrics, car wiring, and how to read the diagrams. That helped a bunch too.)

 

Good catch. Did you notice the tire rubbing the fender on track? I mean, could you hear it rubbing? 

Share this post


Link to post

Where did you take this class?

 

I also took a class on electrics, car wiring, and how to read the diagrams. That helped a bunch too.

Share this post


Link to post

Where did you take this class?

 

My buddy used to train Lexus technicians (he did that for about 16 years). He took me through the electrical course he had for techs. Theoretically, all Lexus techs should have the same knowledge as me (or more, he condensed 2 days into 8 hours) on this subject. I was impressed with it. 

 

Now back to your regularly scheduled programming. 

Share this post


Link to post

Good catch. Did you notice the tire rubbing the fender on track? I mean, could you hear it rubbing? 

 

I don't think I ever heard it rubbing. I knew it had rubbed in the past, but I have raised the car several times since I bought it. I feel like an idiot, because I spent two or three days learning about the ABS system, probing ECUs, tracing wires, even swapping ECUs and other shit... none of it made any sense. I feel like I should have noticed this while routinely inspecting the car. But I sit in a position where I can't see the top of the wheel well and I just don't get in there any turn my head 180* around very often. Oh well.

 

I wish I could get a course like your buddy gave. Actually... Lexus may have it online and I have access to their knowledge system right now, I may go looking for it.

Share this post


Link to post

Very common issue with S13 240SX's as well with a harness that runs right there. Can you extend wires or just pull it outside and route it between the unibody and fender? It looks like it'd gain you a half inch of compression travel over there for big bumps.  

Share this post


Link to post

Apparently this is a "well known" issue and there are many tutorials on how to rerun the wires. They basically just pull out, into the engine bay, and back down again very easily:

 

 

Pulling them out will also make repairing them easy...

 

5c2be498394fe_IMG_20190101_124309.jpg

 

 

Since that's about as far as I can go until I get supplies needed to repair the wiring, I took a few minutes today to drill some new holes in my seat mount and move the seat 1/4-1/2 forward. That should be just about perfect and I'm excited to finally get that done!

Share this post


Link to post

Well, I got the car back together this weekend. It seems to be working correctly now. ABS pump isn't running when the car is off. ABS seems to kick in when the brakes are slammed. We'll see what happens this weekend at MSRH!

Share this post


Link to post

Oops, didn't update the thread after last weekend. Took the car out on Sunday. It did great. Loads of fun to run. Here's a fun session, with my fastest lap of the day on the last lap...

 

 

I definitely need more spring. That's probably what I'll work on next. 950/600 right now, probably go 1100/700 or something like that.

Share this post


Link to post

Put the car up on my lift today. Discovered that my right rear upper control arm has a bad bushing. In theory an easy fix, but to be honest, I'm not sure how anyone can get at the nuts without dropping the subframe. I'm sure I'll figure it out.

 

I was also able to figure out the length of my springs and order some 1100/700 springs to swap in.

Share this post


Link to post

I had to drop the front subframe to install headers once. I replaced the bolts, one at a time, with a piece of all thread. I let the subframe rest on a nut and washer about 8" down. It was pretty easy.

Share this post


Link to post

Car's ready to go now. Rear upper control arms were fairly easy to get back together with the right set of magnets to get the washer on and then hold the nut in place. Springs were easy to swap out. Hopefully I can get some nice weather next weekend and give this stuff a try.

Share this post


Link to post

Slightly related note - I've noticed that once a car gets to be more a dedicated track car, that I've always gotten much more life out of things like spherical bearings, rod ends, and delrin bushings (where they can be used) than OEM type rubber bushings. 

 

Urethane is horrible shortly after install, and they tend to wallow out under hard load and friction, so no one should ever use them for a suspension bushing besides maybe a swaybar bushing with lots of teflon tape and lube. Even then they're a regular maintenance item so a bit of a pain.

Share this post


Link to post

Urethane is horrible shortly after install, and they tend to wallow out under hard load and friction, so no one should ever use them for a suspension bushing besides maybe a swaybar bushing with lots of teflon tape and lube. Even then they're a regular maintenance item so a bit of a pain.

 

Hmm, well, just about everything on this car except these were urethane; now they are, too. Been like that for 60K miles or so, too. We'll see how it goes, I guess.

Share this post


Link to post

Had the car out at MSRH on Sunday. The repaired bushings and higher spring rates felt great. The brakes did not; I believe I need more brake pad than the StopTech Sport. I've got some G-Loc R12s on the way now. I also have some stainless lines to install.

 

In other news, I have a Link ECU on the way, too. Hopefully that goes well.

Share this post


Link to post

In other news, I have a Link ECU on the way, too. Hopefully that goes well.

9,500 rpm here we come

Share this post


Link to post

Had the car out at MSRH on Sunday. The repaired bushings and higher spring rates felt great. The brakes did not; I believe I need more brake pad than the StopTech Sport. I've got some G-Loc R12s on the way now. I also have some stainless lines to install.

 

In other news, I have a Link ECU on the way, too. Hopefully that goes well.

 

Interesting so what were reasons of going to aftermarket ECU?  I was under impression there wasn't a lot left on the table for the 1UZ.  

Share this post


Link to post

Interesting so what were reasons of going to aftermarket ECU?  I was under impression there wasn't a lot left on the table for the 1UZ.  

 

A few reasons:

 

I believe the car is in a limp-like mode. The stock ECU wants to see things that aren't there anymore because the automatic transmission is gone and the car is "stuck" in neutral. There is some debate over whether this matters, but I think evidence is there to demonstrate that it does. An aftermarket ECU will obviously eliminate this. Here's an example before/after dyno from another 1UZ VVTI motor that went manual and faked the missing solenoids and sensors:

 

5c62cfdd80cfd_all4swap.jpg

 

 

Also, the Toyota ECU is quite locked down. I would like to extend my RPM limiter a bit. If you go back and look at my dyno sheet, I believe the engine could use another 500-1000 RPM. Everything I've read says that the stock motor can handle that without issue. I don't think there's a huge amount of power up there, but it would make a few corners on the track a lot better. (Of course, if I end up getting more power, then it may be a moot point as I'd have to go to 5th sooner.)

 

You might be right about the 1UZ being fairly tough to get anything out of, but mine has headers and ported heads and intake manifold, so it isn't stock. Maybe the factory ECU can take advantage of these things, but that seems unlikely?

 

I also want to build a "better" motor for this thing, you know, with real cams and heads and other fun stuff. We'll see if that ever happens, but an aftermarket ECU would be a requirement for that, so I may as well get it in place now.

Share this post


Link to post

Interesting so what were reasons of going to aftermarket ECU?  I was under impression there wasn't a lot left on the table for the 1UZ.  

 

There is and there isn't. Depends on how far you are willing or can go. If you have to keep OEM headers, ECU, can't dig into the head, then there's not much on the table. On the other hand if you can run aftermarket headers, improve flow in the heads, throw cams at it, and run a standalone ECU there's some decent power on tap. I've been reading up b/c GONK started a monster with this whole SC400 voyage. The intake side of heads is apparently a big bottle neck, poorly desinged.

 

http://www.themotorhood.com/themotorhood/2017/9/6/tuning-guide-how-to-modify-your-1uz-fe

Share this post


Link to post

Wow owned two of these bad boys and learning a lot right now. Miss my SC400.

Never too late to own a third :)

Share this post


Link to post

Received a few packages yesterday:

 

5c65718d76fa9_LinkECU.jpg

 

The Panic harness seems nicely done. I shouldn't have to do much to get things going: install IAT sensor and MAP sensor, plug things in, calibrate a few sensors, and go. I have a windband sensor setup on order that will feed into the ECU at some point, but that shouldn't be required to get the car started.

Share this post


Link to post

Sweet! I think a good standalone is very valuable once you do anything more than minor bolt-ons to a car. If nothing else it makes troubleshooting so much easier having all the ECU data right there, readily accessible, and no hidden voodoo/limp mode stuff potentially happening.

 

BTW - I would be *really* cautious driving much on it without a wideband. Base maps can be really far off, especially if you've really modded your engine, and you can do damage if you run it super rich or lean for long. It's also likely to frustrate you if you're just guessing on what's going on with the engine without data. You probably realize all this, but it's just not worth the damage/frustration to put off a wideband.

Share this post


Link to post

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...