Bad Ecu

[Musada]

I have a 1990 Lexus LS 400 and had been having the following problems.

For a while whenever the check engine light would come on, the car seemed to run normally, but when there was no check engne light , it didnt seem to want to idle. I took it to a shop and had it diagnoed and they told me it wa the MAF sensor. So i chhanged that and nothing was fixed. Also changed the ignition coil on the top of the engine and nothing. A week ago i was riding on the high way when the car jerked twice as if the engine was shutting down, and when i finally made it home, it shut off completely, and never came back on. My father replaced the fuel pump and it started right up, but the check engine was still on. 5 mins of driving and it shut right off and didnt restart for another 10 mins. When we finlly got it started it ran fine for another 10 minutes before just shutting back off.

I have also changed my plugs maybe 3 times this year hoping to resolve.

I found this guy on craigsist and explained the problems and what was done to try and resolve the issues. He immediately said the ECU was bad, and that this is common in ls400s, and that he'd rebuild mine for 175.

I just wanted your opinions on this, whether or not i should go through with this, I'd rather not waste anymore money if I dont have to

Thanx guys!

[SRK]

I can understand your concern. You've wasted enough money on things that have nothing to do with an intermittent stall. Spark plugs - all eight - rarely all go bad enough to cause a stall, and once changed for new, won't. Fuel pumps don't trip check engine lights. You changed one coil, and left the other in place. Did you find the one you changed faulty? Did you determine the one you didn't change OK? MAF's rarely go bad, and when they do, the engine goes into limp home mode. The code is specific. Usually when the ECU fails it will also trip a code.

So no, don't fool with the guy on Craigslist. Get the codes that are in the ECU now identifed correctly and then determine if they actually point to faulty part. The code doesn't always mean the part has failed, many times only that it's out of range, and that may be caused by something else that doesn't trip a code.

Stop buying parts for it until the real fault is identified.

From your description I'd say a bad crank position sensor, but don't take my word for it - diagnose it first.

[landar]

Very good advice from SRK. Check the codes first. Here's how -> http://www.lexls.com/tutorials/intro/codereading.html

[Musada]

Thanx for he advice, i checked the engine code, and it sent backa code 14, which im seeing mans ignition no.1 signal...would that mean to check igniter 1, and ignition coil 1? from the diagram i found, i believe thats the ignition coil i had changed a year agoI don't believe it's if ignition coil, and my pops said its on om all 8, how do you test the ignitor

[Musada]

well my father said all 8 cylinders are firing, and i dont believe its the ignition coi, because i just changed that, and he symptoms aare completely different from the last time it went out. (the last time it went outt, the car wouldnt go over 20 mph, the exhaust was burning red, and it was smoking. The car runs fine, it just cuts off.

hw do you chek to make sure ignitor 1 is bad?

[SRK]

It's tough to tell from this distance. However the ignitors switch the coils and AFAIK each coil has it's own ignitor. So therefore an intermittent ignitor would not shut the engine off - it would run on the remaining four cylinders.

Is there a remaining code?

A fuel pressure check would be in order. Could be a fuel pump fuse or relay.

Simple stuff first.

[Musada]

I got some igniters from the junk yard, and am no longer getting the 14 code, the car has not shut off yet, however, while I was riding on the highway it did feel as if the engine was about to shut down.....it did it about 3 times, but never shut off. A code 13 does still remain though, I have changed the MAF sensor....any ideas what could be causing the engine to try and shut off?

[steve2006]

A common fault is the driver's side coil failing or breaking down when warm something you haven't replaced and for around $30.00 worth a shout.

Are all the ignition components in good order, dizzy caps, spark plug leads, the leads from the coil to the distributors and the rotor arms in the distributors.

When it is dark start the engine, lift the hood and look for signs of arcing from the spark plug leads or coils. Taking off the covers will help you see better.

[Musada]

I actually had replaced the Ing ition coil on the driverside a year ago....but ill check the sparkplugs

[Banshee365]

That person saying that LS's are known for ECM problems is good for his business. I don't think your model year LS had many ECM problems. Most ECM problems are with the 95-97 cars. I have a 96 and have, myself, experienced a failed ECM and BOY is it hard to diagnose. Not saying that your ECM isn't bad but keep your eyes open. It would be great for you to find someone local with your same year car to swap ECM's with just to troubleshoot. If your problems are very constant and can be replicated easily, swapping your ECM temporarily with a known good one from another car could be a quick and precise troubleshoot as far as the ECM is concerned.

[Musada]

I'll be doing a tune up this weekend, and figured I'd check the connection to the camshaft sensor, anyone mind telling me exactly where the sensor is located, maybe post some pics or a diagrams

[fsuguy]

SRK,

Can you post a quick method to test the pressure system? I have a suspicion my pressure is low, but not sure where to make the connection of the pressure gauge, etc.

Thks

[Musada]

Anyone have a diagram for the location of the camshaft position sensor

[Musada]

Well i didnt see any sparks or loose wires....So far I've replaced

-Igniters

-Spark Plugs

-Fuel Pump

-Fuel filter

-MAF

We though the issue was resolved, after I drove it home, about a 30 mile drive. I had no problems. The next I was driving to work and the car just cut off....again....and wouldnt start once again. I had to get it towed back to my dad's place. As soon as we unloaded the car, I went to start it and it started right up! Anyone have an suggestions. My father and uncle seems to think that somethings getting hot that causing it to cut off. I called this mechanic and explained to him what was going on. He said the crankshaft sensor is out, and thats whats causing it to cut off, and not start til the car cools down. I thought that if the crankshaft sensor was bad, it would start at all. My problem is the car starts, and then shuts off randomly, and wont restart.