Banshee365

Car is stuck at a jiffy store right now. It's done this in the recent past. It will run fine, then you shut it down and it won't start back up. IF you can get it started back up black smoke pours out of the exhaust, telling me it's flooding out. It tries to start just a tad so I know it's getting some spark. After it starts it'll start and run fine for a few day's then do it again. The motor has 203k on it and doesn't burn any oil or knock, tick, or anything. This car has soo many issues like low/high idle all the time and now this starting issue. Any ideas? I'm about to go tow it home with a strap. Getting so sick of this car breaking all the time. Is my ECU going bad?

-Kelly

Banshee365

Went back to the Jiffy and tried to start it again armed with a tow strap and an SUV. It was hard to start but finally hickupped enough to put the gas to the floor and it revved up and blew tons of black smoke out. The car idle's around 1,200 in neutral and smals into gear because of it. When you rev from idle it hickups and drops a hundred or so RPM then revs. Seems to be running really rich. A Snap-On scanner at buddies shop shows the ECU thinks the ECT is like 150 tops. It has a brand new OEM ECT sensor. A family member following me with the tow vehicle said the car reeked like rotten eggs. Yet another sign it's running rich. What the in hey is going on? Are my cats bad or something? They're not glowing red. Now my CEL is on again with the P0112 or whatever it is showing to a coolant temp sensor circuit malfunction even with the brand new sensor! I've wiggled wires at the ECU and no intermittent problems were found doing that. The car was shuttering and bucking a little at speed as well. This car is meticulously maintained and was very reliable until very recently. I REALLY need some help here guy's. If you're reading this and have some input, by all means please contribute anything. I'm starting to suspect the ECU but can't afford the money for trial and error fixes, you know?

Banshee365

Drove the car some more today. It started up perfect this morning and after a minute or two idle right where it is supposed to. First stop light I come to it's idling at 800-900 in gear and 1200 out of gear. Shut it off at an errond and it's hard to start again. Finally starts and smells like tons of rotten eggs when it starts. Now it idles at 2200-2400 out of gear and 1,200-1,300 in gear. The car goes 50 mph without touching the gas. The throttle body is closing all the way and I don't see how the IACV can cause an idie this high with as small as it is. It also function checks perfect out of the car. There are no air leaks either in the intake system. The CEL is still on for P0112 for coolant temp sensor circuit malfunction. The last step in the factory manual diagnosis is to replace the ECU. Is my ECU going bad or is it cats, o2 sensor, iacv, throttle body, wiring harness? I really need some help figuring this one out. Times are very tough and we can't afford a new car and can't afford 2-3k in parts to "trial and error" this problem. I wish I knew someone with the same car that I could swap ECU's with. What's the best place to get and ECU for a 96 LS?

Banshee365

Bump.

Still can't figure out what's going on. Could a fuel managment component cause the rich running issues and very high idle? It's start and run just fine until it starts to warm up then it starts running horrible.

Banshee365

Bump please. Car is acting crazy can't even trust it leaving the driveway. Is my ECU bad? Coolant temp circuit malfunction and rich running condition.

gmacrae

It sounds like there are a few problems there. Im thinking there is an intake leak (or two)... maybe a faulty MAF sensor... have you tried running the car with the MAF/AFM unplugged?

JimsGX

I'm curiuos to know how the car would run/behave with the MAF sensor unplugged...

polobai

Check the wiring to your coolant temp sensor. Check for continuaty between the plug and the ecu wires...its probably a broken wire.

Banshee365

I finally got home to work on the car some more. I started the car up this morning and it started just fine. Idled high for the warm up and slowly returned down to 650 or so after a couple of minutes. While sitting at the normal idle I reved it a little. The motor would hesitate at first and drop some rpm's then rev up, as if it's running rich or something. I then shut the car off while it's still kind of cool and unplugged the MAF. The car would hardly run with it unplugged. IT wouldn't idle and it ran very rough. Hooked it back up and all was well but it still hesitated during reving. Can o2 sensors without codes cause the car the run bad?

gmacrae

With the MAF unplugged i assume the car runs a 'limp' map using TPS vs RPM. Also, o2 sensors are ignored for the first few minutes of cold running. Have you checked your TPS? Im not sure, but i think the car will run if you unplug the TPS (but plug MAF back in). See how that goes.

Banshee365

Thanks a bunch for the reply. I hoped I had replied to my posts' that related to my LS running really bad. I've since fixed the problems.

The ECM in my car was the problem. The reference voltage for the ECT circuit was over 8V when it should have been 5V. It was jumping all around, must be a faulty transformer, voltage regulator, etc... or something. I bought an ECM from a salvaged car that was known to run good before parting out and put it in my LS and it's like a new car now. I couldn't get rid of P0115 with the old ECM. The voltage or something was spiking causing the ECM to think the car was -40*C for a split second and it would trigger the CEL. When the car was hot, IF you could get it started, it would idle around 2k and maybe settle around 1,500 if you were lucky. It smelled really bad out the exhaust, so I thought the cats were going bad. The ECT circuit was causing all of my problems. The car never thought it was warming up. Thus causing the ECM to dump fuel into the engine making it run rich and flood out when hot. It would flood out like a weed wacker and it wouldn't start hot. By unplugging the ECT sensor the ECM defaulted to thinking the car was 176*F or so, which as way hotter than it thought it ever got. The car ran much better but was very hard to start cold that way because it wasn't delivering enough fuel. The ECT sensor data never went above 120*F when hot. Replacing the ECM has made the car feel like a new car. No stumbling, way more power, awesome starting at whatever temp, much better gas mileage and no more CEL. It's put a whole new life back into the car.

One thing I hope anyone who reads this will see is that you HAVE to do your research and troubleshooting before you buy parts. Think outside the box. If you're LS (especially a '94 or '96) with over 200k miles is having weird problems, consider the ECM along with other things unless it's completely obvious. My Lexus parts guy say's he sells alot of 94 and 96 ECM's to customers with over 200k miles. He also told me he has customers demanding they know what the problem is and they buy IACV's, cats, o2 sensors, MAF's, and such when it was the ECM the whole time. They wasted ALOT of money. The ECM seems to be a wear item and as the car's drive over 200k they seem to start failing more often. I've since replaced my leaking evaporator core and compressor with used parts and charged the system up with 1.6 lbs of R134a and finally got the AC working and it's like having a totally different car. By doing research, holding off on buying parts until I knew for sure what the problem was, and doing all of the repairs myself; I was able the take a 205k mile car that was broke down in a jiffy store with no AC to a running like new car with freezing fully functioning AC for $500 including the almost $100 AC evacuation and charge.

-Kelly