YotaMitch

Hey I'm new to the club Lexus forums, my names Mitch. I recently purchased a mint 93' ls400 down here in London Ontario, Canada and having some troubles with it. I've done a ton of research on my problem and have come up with a wide array of problems it could be. I'm not made of money I believe in a proper diagnosis rather then just dumping money into something that has a simple fix. I'll try my best to name the symptoms. Prior to this, I have installed new plugs, caps and rotors to get rid of a misfire which I thought was my problem. Car ran AMAZING after I look a 5 min drive, when I got back it died on me.

Symptoms:
-running very rich, black smoke coming from the tail pipes.
-idles around 200rpms when I can get it to idle on its own, then it usually dies out shortly after
-has no acceleration, 0-60 in 10 seconds or so (much faster after I did the plugs etc.)
-won't rev over 2000rpms in drive, or 4000 in park

I work at a shop and I've had a few mechanics took at it, it's obvious it's a metering issue with the air/fuel ratio because it's running so rich it seems to be choking itself out because it doesn't have enough air. I have a couple friends with sc's and they all seem to think it might be the IACV, seems to be a common problem. I'd appreciate any advice you may have, I am new to the 1UZ so I am learning as I go. Thanks in advance.

RA40

iTrader: (6)

Welcome to Club Lexus.

Several possibilities and further discussion about these are in the 2-LS FAQ (They overlap with the 1-LS so the discussions are listed there):

ECU : https://www.clublexus.com/forums/ls-...capacitor.html
ECT:https://www.clublexus.com/forums/ls-...read-this.html
Can be an IACV so worthwhile to go through because these are not uncommon maintenance areas.

YotaMitch

Thanks RA40. I will take a look at the links you posted. I really hope it's not the ECU but it has a lot of similar symptoms unfortunately.

dicer

Could be's........

1 Cold start valve leaking.
2 Engine temp sensor
3 O2 sensors
4 ECU
5 Leaking injector
6 IAC

Also check fuel pressure

Yamae

It simply means that your car is in the limp home mode. The main processor part is not working right and the sub-processor is working but it limits the rpm up to 2000rpm.

I'd quickly check the ECU measuring the ripple or simply replace QAS capacitors.

YotaMitch

What is the start valve? As well my tach and speedo do not work regularly, just intermittent. Is there a way I can test my ecu? I am not able to connect with a scanner to either obd port, just comes up saying it has a communication error. Do you think this would be a good sign my ecu needs capacitors?

A couple of guys at work suggested checking the fuel pressure, which I will do in the next couple days after I put the IACV back on (just took apart and cleaned w/ carb cleaner). I really appreciate your advice, it helps out huge.

YotaMitch

How would I go about measuring the ripple? I am thinking a lot of my problem has to do with the ECU but I don't want to rule out the same simple stuff as well. Limp mode makes sense, it is very sluggish.

dicer

Here is one write up for it. I think its for gen 2, its a bit more difficult for some gen 1's.
https://www.clublexus.com/forums/ls-...-by-yamae.html

YotaMitch

Thanks dicer I'll check it out!

dicer

Cold start valve is the 9th fuel injector. It injects extra fuel for cold start ups.

YotaMitch

Thank you!