BryceL

Hey there, just bought a 95 SC300. It has 189000 miles on it.
I haven't had very many problems with it. But when it has problems it happens at the most random times.

I'll be driving perfectly fine and the engine just shuts off. Just literally stops as if i turned the key to the off position. The wheel and brakes generally lock up too - meaning that i can press the brakes and move the steering wheel but it takes damn near all my strength. Usually I can put it in park and restart it with no problems, but it occasionally will turn over without starting and i'll come back to it a couple of minutes later and it starts great. I should also mention that the lights and radio will continue working when this happens.
I have also noticed it sort of lurches when it shifts. It doesn't feel terrible but it is noticeable. I figured this was normal for these cars until i realized sometimes it shifts seamlessly.

There was one instance where the engine had shut off, i restarted it and started driving it, and noticed it was having a very difficult time shifting from 2nd to 3rd and it was lurching very bad. It felt as though It really wanted to shift but just couldn't do it. I immediately pulled off into a mechanics garage and they came out to look at the car and it started and drove like a dream.

I took it to a mechanic to have it checked out because the engine light was on and figured that was it. the code came back as code 71 EGR Flow Problem. He said that the EGR Valve needs to be replaced but that would not cause the problems I'm having. They kept it for a week and reported it "never having problems shifting, running, or dieing."
WTF?
Like I said, it happens very randomly.

From the research I've been conducing, Could this possibly be an ECU, feul pump problem? Thank you all for any advice or tips.

SC400slide

iTrader: (11)

Welcome to Club Lexus! Sounds to me like it is the ECU. (Even the fuel ECU, but not as likely) Personal experience, my 92 SC400 lurched when downshifting. Had the ECU rebuilt and the lurching stopped. The guy who rebuilt my ECU told me he was surprised the car was even driving based off the internal condition of the ECU capacitors. Your's probably will look similar if it has never been touched.

t2d2

iTrader: (8)

Good job on the first post research, you nailed the most likely culprits. Get that ECU serviced or replaced before throwing money at anything else. There's a good chance it'll solve the problem, and assuming a previous owner hasn't already replaced the capacitors, it's going to need servicing soon if not already.

I had occasional start-stall problems that didn't fit your pattern, but that went away after servicing the ECU and dumping the fuel pump ECU. Of course, I also messed with everything else in the fuel system in between, so I really have next to know idea which of a dozen things eliminated the behavior.

The code 71 EGR shouldn't be an issue. I yanked my EGR system when one of the pieces broke while removing dry rotted vacuum hoses. You could go that route or look for used replacement pieces. They cost a small fortune new.

BryceL

Thank you for the advice. I'll take out the old ECU and take some pictures, I plan on sending it off and getting a new one since the general consensus is that this is the problem.
Any suggestions on reliable businesses who fix, or sell ECU's that don't cost a fortune?

BryceL

I pulled out the ecu and the capacitors had leaked ever so slightly. Not extremely noticeable but enough for me to send it off to a place called circuit board medics.
They had good service and fast turn around. It took about a week to ship it, fix it and ship it back.

Once reinstalled the I noticed a difference driving around. It still slightly lurches when shifting. And the engine shut off in the middle of highway traffic. (I noticed that it seems to only happen when I get back to first gear or am idleing) I put it in park and restarted it no problems.

So I guess the ecu is not the culprit. Would you guys say to throw money at the fuel injector ecu next?

Also any other tips or services to help doing so?

Thanks again for the feedback.

t2d2

iTrader: (8)

Try bypassing the fuel pump ECU with the Fp and +b pins jumpered in the diagnostics box. If that helps, then you've got the option of permanently bypassing it or buying a replacement.

BryceL

Ok i tried that. I heard the hissing of the fuel releasing and also a hum near the gas tank, but it still wouldn't start. Does this mean that the Feul ECU is bad?

t2d2

iTrader: (8)

No improvement means the part you bypassed wasn't the issue, so something other than the fuel pump ECU is the problem. That's about all I've got, though. Hopefully, someone else can chime in with other suggestions.

sjc2467

I'm not sure if this can happen on your Lexus, but on many cars, if the EGR valve sticks fully open, it will make the engine stall at idle. (It still wouldn't account for the shifting issue, though). This is usually pretty easy to test: trace one of the EGR gaskets on a piece of thin aluminum (something like a soda can, not as thin as aluminum foil), cut it out just around the perimeter (with no hole(s)) and use that as a gasket to block off the EGR passage. If that fixes your problem, you know it's the EGR valve sticking open. From there, you can either fix it properly or permanently block it off (soda can aluminum will burn through in a few weeks, so it's not a permanent solution). It might be a long shot, but it's pretty quick, easy, and cheap to test.

BryceL

FIXED!!! I had no idea these cars were so fast! she flys now!

I figured out that someone who had worked on the car before me had disconnected the ground wire for the fuel injector harness from the engine. the wire was hidden - lodged up underneath the engine where I couldn't see. When that was reconnected everything started and ran like it should. The reason it would run sometimes is that the ground wire would bounce around and occasionally touch the engine and get a ground.

It turns out that the shifting was a problem that was only lightly related.

It's crazy all the problems that one small little thing can cause. Now that it reliably starts up and drives, I realize that It shifts better than before now, but is sill sluggish and weak. I plan on servicing the transmission next. changing the fluids and putting an additive of some sort. I'll let you know if it helps.