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my SC starts and idles fine for one maybe two minutes and the starts running really rough, just like you hit a switch and its a different car - while driving it will sometimes clear up but, for the most part at red lights and low rpm it has a real rough idle - it won't accelerate and falls on its face if you try to throttle into at low rpm's - at faster cruising speeds of 50 and above it seems to accelerate somewhat better - changed the plugs, wires, caps, rotors, fuel filter, mass air, check and changed most vacuum lines - need some advice
didnt read through this whole thread but your ecu does look bad another thing if you guys are having problems with your car missing out running at half power and sometimes clearing up then swap your ignition coils. I redid my ecu changed sensors and so on and of course i had a bad coil on the drivers side. I dont exactly agree with everyone pushing to redo your ecu but sometimes that can be the cause. If you get a coil from autozone the ones around here did agree to take it back if it didnt fix the problem even if it does take it back and order some cheaper ones and just replace both.
Did you change the spark plug wires or the distributor recently? Is the CAT glowing red?
I've, changed plugs, wires, cats, mass air, fuel filter, some vacuum lines, caps rotors - when you crank it, it runs clean, it idles real high, around 1300 rpm's and doesn't have a miss, it accelerates good and seems to have power and not miss but, a few minutes and the idle drops and it starts missing and at low rpm's has no power - while its jerking leaving the red light and you try to throttle through it, it falls on its face - then it will clear a little and go - at higher rpm's it runs better but you can feel a little miss in the peddle but, it has power to accelerate if you keep the rpm's up - sometimes it has better days than others but, for the first two minutes every morning you wouldn't know anything is wrong except the high idle.
Sounds similar to a prob I had with a 98. Runs perfectly for a week, then stumbles all over and then doesn't start. I changed the capacitors on the ecu and it ran for a week really strong.. a whole tank went through it.. then gave it back to the owner and it died within a day. Someone is looking at it now they think it's an intermittent fuel pump issue.. so going out.
I think looking at the ignition coils is a good idea too but this car doesn't put out any codes...
Did you change the spark plug wires or the distributor recently? Is the CAT glowing red?
The reason I asked is that I had a similar intermittent problem where the car would run on only 4 cylinders, and the CAT would get red hot. It turned out that the high tension wire on the driver's side was shorting out whenever it came close to the chassis. I used crappy non-OEM wires that didn't have enough insulation. I put the original wire back and had no further problems.
It's simple enough to diagnose -- just jiggle the wires around while the car is running. It's a long shot that this is your problem, but running on only 4 cylinders is a possibility nevertheless.
The reason I asked is that I had a similar intermittent problem where the car would run on only 4 cylinders, and the CAT would get red hot. It turned out that the high tension wire on the driver's side was shorting out whenever it came close to the chassis. I used crappy non-OEM wires that didn't have enough insulation. I put the original wire back and had no further problems.
It's simple enough to diagnose -- just jiggle the wires around while the car is running. It's a long shot that this is your problem, but running on only 4 cylinders is a possibility nevertheless.
It really does feel like its running on 4 cylinders - when it's missing at idle I've noticed that the head lights are dimming out real bad - OK, leaving a read light I have to shift it manually, if I can get the rpms up to 2000 It will accelerat with power - as long as I keep the rpm above 2000 it drives BUT anything under and it will spit and sputter and will pot through the exhaust and if I can get it through it by easing on the gas real slow to get the rpm up it will accelerat SO I drive it by manually shifting and going in and out of overdrive also...
It really does feel like its running on 4 cylinders - when it's missing at idle I've noticed that the head lights are dimming out real bad - OK, leaving a read light I have to shift it manually, if I can get the rpms up to 2000 It will accelerat with power - as long as I keep the rpm above 2000 it drives BUT anything under and it will spit and sputter and will pot through the exhaust and if I can get it through it by easing on the gas real slow to get the rpm up it will accelerat SO I drive it by manually shifting and going in and out of overdrive also...
The only time it doesn't do this is when it is completely cold and been sitting all day or first thing in the morning - it will crank and idle high and drive and accelerate fine for about a mile and then all hell begins- also, the longer its running the worse it gets till its undrivable
I was not sure where to post this but thought this thread as good as any. I am replacing my TPS on my LS 400 and came across the following tutorial: http://www.lexls.com/tutorials/EFI/tps.html
In the tutorial the issue of testing the TPS while on the engine is discussed. Well, there is a simple tool to fix this and probably everyone has one. On PCs there are always several extra power cables (pigtails) for the hard drives and floppies. You can cut one of these out and not really bother the computer. With little sanding these will fit the TPS sensor so you can do testing while the unit is mounted. I have attached a couple of pictures. But I have a question about instructions #7&8. The instruction is to rotate the sensor until "resistance on the ohmmeter is gone." And then in instruction 8, without additional changes "there should be continuity" between the same two terminals. Does resistance gone mean zero or as I can only read small ohms or nothing? Any ideas, thanks? Look at the tutorial to see the terminals discussed.
6) Connect an ohmmeter to the IDL and E2 terminals of the TPS. Unless the throttle body is removed it's pretty much impossible to do this using the standard ohmmeter probes. There's just no room and plus you need to be able to rotate the TPS. It could probably be done using some very tiny clips.
7) Turn the TPS clockwise until resistance on the ohmmeter is gone and then tighten the two screws.
8) Now use your ohmmeter to check for continuity between terminals IDL and E2 with the 0.40mm thickness gauge still inserted between the throttle stop screw and lever. There should be continuity.
9) Now insert a 0.85mm thickness gauge between the throttle stop screw and lever. There should not be any continuity.
10) Replace the throttle body cover, plug the connector back into the TPS, and go for a test drive.
Just my experience but my brother had this same issue for months with a 93 ls400. I ended up buying the car from him and ended up replacing the ignites and that solved my problem. I didn't read all the posts but the couple pages I did read it was never mentioned.
I didn't want to start a new topic on this I have a 1991 and been going through this forum trying everything having basically the same problems and more.
When I say I've tried everything twice and then again it hurts to think about it. After replacing every relay, ignitor,plugs, distributors, ecu, caps in ecu, and so on I had the car drivable. After a few days I figured what can it hurt to finally open her up well It did ended up dieing on me luckily I was about half a mile from home at the top of the hill going a decent rolling speed when it happened I was able to roll home in neutral a little over half mile into my driveway.
Aboutthe a week into it I was done ready to push it down a hill on fire and walk away from this headache after deciding I'll give it one last shot I did again everything has been replaced checked more then 2-3 times in the last four months.
Switching between two ecus out of 4 that I rebuilt and tested on other 91-93 ls's proved to work great ended up finding 2 of my oem wires would not give any resistance readings and a relay that I replaced twice actually both of them by the ecu forget what they are right now but they are green by the ecu I'll try and post some pictures of the one that happened to give me same exact problems as bad ecu. Looked like it threw up inside how I have no clue it was good when I put it in I disassembled it and checked before.
LaSt but important at least to me it seems now I always had the car running without issue maybe running rich without having the intake assembled completely just hanging to the side from pulling and checking plugs and so forth it would start then die but ran OK when feathering the throttles over 2k rpm. I decided to put it together call it a day and start it one last time what do you know ran like I've never heard or felt before. I test drove it and wow. Long post I know but with all the frustration I've had with this car had to vent somehow.
-replaced everything 2+ times
-about toto give up found 2 to newish oem plug wires dead
-relay by ecu looked like it threw up inside replaced almost fixed starts then dies
-installed intake back not hanging off to the side in two parts
Finally started idled perfectly no cel.
--test drove and been driving like a new car last few days after 4 months of well you know your reading this.
you are this might add to this and maybe help somone. I had replaced this exact one about 5 weeks ago and before I did I opened it up checked it everything was good how this happened beyond me.
01-11-15, 03:24 PM
1993 sc400
