Keisler Posted January 17, 2006 Share Posted January 17, 2006 I am having problems with my 92 SC400. This thing has baffled me. Sometimes it will start and sometimes it want. I have changed the battery, alternator, starter and still have the same problem. When it doesn't start it will turn over and over but there is no fire at the coils (either of them 2). All wiring appears to be good. Also does anyone know where the ignition relay is located on the 92 SC400. I am chasing my tail here any help greatly appreciated. Quote Link to comment Share on other sites More sharing options...
LexInfo Posted January 17, 2006 Share Posted January 17, 2006 I am having problems with my 92 SC400. This thing has baffled me. Sometimes it will start and sometimes it want. I have changed the battery, alternator, starter and still have the same problem. When it doesn't start it will turn over and over but there is no fire at the coils (either of them 2). All wiring appears to be good. I am chasing my tail here any help greatly appreciated. You might want to check both of the cam sensors located on each sides of the cam sprocket and especially the crank sensor on the engine with an oscilloscope but a voltmeter can do also. its better to check the signal at the engine ecu to elimate all the possible wiring fault. also there are two igniters located around the master cylinder area which controls the primary ignition circuit and also confirms the ignition signal to the engien ecu. some rare cases they go bad, but i would not replace them with out checking the basics first Good luck .... Quote Link to comment Share on other sites More sharing options...
Chaotic1 Posted August 12, 2007 Share Posted August 12, 2007 i know this is an old post but i cant stand questions w/ no answers! the ignition relay is located in a box behind the battery. turn the lid to the box upside down and you should see IG2, thats the ignition relay. im having the same problem with my 1992 SC400, no spark from both coils. i have a mitchell1 manual which covers everything pretty comprehensively but i would like to get my hands on those books put out by lexus. im getting just about batt voltage at the coils when the ignition is on, but no spark. checked both cam position sensors and the speed sensor, sensor plates - check, cleanliness - check, and all three are around 1153 ohms. the only thing i havent checked is for continuity between the ecu and the sensors. whats the procedure to expose the engine/trans ecu and does anyone have suggestions as to what to do?? Jarrod Mello Quote Link to comment Share on other sites More sharing options...
jonesmatty Posted August 21, 2007 Share Posted August 21, 2007 I'm having a similar problem with my 92 SC400. It was running extremely rough and I though it was just out of time. The mechanic replaced the coil and it ran fine for a month. Last week, it started with the same problem barely running, I step on the gas and it sounds like a VW bug trying to get going, sputtering at probably half power. I ran the codes and came up with 21 and 25. But I'm having trouble figuring out exactly what those mean. All this with a frozen AC compressor and I'm not sure if I want to put to much more money into it. Any suggestions? Quote Link to comment Share on other sites More sharing options...
VincyRay Posted January 9, 2008 Share Posted January 9, 2008 This sounds a lot like the problem I'm having w/ my '93. Did you ever get it resolved? Also, on mine I noticed that on one of the coils, I read 6V from one wire to the other going in to the coil, and none on the other. But when I ground to the battery, I get a full 12V. I started to try just grounding the other wire to the battery and see if it would start, but decided that I should make sure that they should both be reading 12V there before I go that far. Quote Link to comment Share on other sites More sharing options...
bolo_fd Posted April 29, 2008 Share Posted April 29, 2008 anyone got any answers for these q's, i'm having the same problem. only half of my engine is working the other half has a really weak spark. how do i test the coil and ignitor? any help will be greatly appreciated Quote Link to comment Share on other sites More sharing options...
vamp26 Posted August 27, 2008 Share Posted August 27, 2008 I'm having a similar problem with my 93 SC400. It tries to start and sounds like it should but its just not firing all the time. I've found that if I try starting it in short bursts it will catch as well as letting off the ignition quickly. When it does fire, it seems like it idles low and rough for the first second or so and then runs fine. This is a recent purchase and I have next to no knowledge on the workings of this car or where things are located. I took it to a Toyota dealership for a diagnostics test but they couldn't pinpoint the problem either. They suggested the fuel filter or possibly the crank position sensor but I have no idea. Any advice for where to start would be much apreciated!! Quote Link to comment Share on other sites More sharing options...
tonyw Posted August 27, 2008 Share Posted August 27, 2008 I'm having a similar problem with my 93 SC400. It tries to start and sounds like it should but its just not firing all the time. I've found that if I try starting it in short bursts it will catch as well as letting off the ignition quickly. When it does fire, it seems like it idles low and rough for the first second or so and then runs fine. This is a recent purchase and I have next to no knowledge on the workings of this car or where things are located. I took it to a Toyota dealership for a diagnostics test but they couldn't pinpoint the problem either. They suggested the fuel filter or possibly the crank position sensor but I have no idea. Any advice for where to start would be much apreciated!! Here's the thing with these cars, if one thing is bad or not working properly, the whole car doesn't run right. I have done just about everything a person can do to my 92 SC400 to no avail. I have changed the ignitors, ignition coils, plugs and plug wires, MAF sensor, TPS sensor, Distributor rotors and caps, camshaft position sensors, fuel filter, fuel pump, engine ECU 4 different ones, fuel pump ECU, EGR valve, and I just ordered a crankshaft position sensor. had the alternator checked, cleaned the fuel injectors, cleaned the throttle body and upper intake, did a complete wire check and fixed some cracked wires, its got a brand new timing belt and water pump, and a new battery, I can crank the engine and it will turn over but still does not run. I have had this car at a lexus dealer 3 times and they could not fix it any time. I think it's mostly because of it's age. If you don't know anything about this car you better learn fast or it's going to come back and bite you very hard. And its not cheap. I have learned this the hard way. I would love to have this car running, there are alot of possibilities with it, but I don't think its going to happen. Quote Link to comment Share on other sites More sharing options...
UCF3 Posted August 29, 2008 Share Posted August 29, 2008 Didn't we talk about this start-up issue on a different post? I remember mentioning the timing belt, the spark plugs and wires, and the other person was afraid the ECU would have been the problem. Is that you? Quote Link to comment Share on other sites More sharing options...
tonyw Posted August 29, 2008 Share Posted August 29, 2008 Didn't we talk about this start-up issue on a different post? I remember mentioning the timing belt, the spark plugs and wires, and the other person was afraid the ECU would have been the problem. Is that you? Yes that was me, I am still having the same issues, I am expecting a new crank position sensor today, and i'm replacing the IAC valve as well, from a 90 LS400 that was wrecked last week. as soon as I get those replaced I will be checking the timing, the timing belt and water pump are 4 months old, so I hope I can get this done. If anybody has an more suggestions please don't hesitate. thanks Quote Link to comment Share on other sites More sharing options...
jamesblacklexus Posted September 4, 2008 Share Posted September 4, 2008 Didn't we talk about this start-up issue on a different post? I remember mentioning the timing belt, the spark plugs and wires, and the other person was afraid the ECU would have been the problem. Is that you? Yes that was me, I am still having the same issues, I am expecting a new crank position sensor today, and i'm replacing the IAC valve as well, from a 90 LS400 that was wrecked last week. as soon as I get those replaced I will be checking the timing, the timing belt and water pump are 4 months old, so I hope I can get this done. If anybody has an more suggestions please don't hesitate. thanks new here hope this reply goes thru and can figure out how to navigate theu here. i had the same prob car start and for sec like it might die and then wont start sometimes. i looked at plugs cuz all electrical and fuel was eliminated. so only left ignition. looked at plugs . the sc400 is 32 valve and old valves can leak and everyone has abt same comlaint for abt same year mine is 93. i really think that the plugs are getting oil on them. its simple the plugs go in middle of head and very easy get oil from a partially leakin valve seal. not to smart when comes to cars btu mine would not start changed plugs saw oil on them and started right up then it wouldnt im considering doing valve job on her but think had to do w oil leakign in the head its like a hemi. where the plug in middle of head. and a older car makes since that will not spark w oil going on plugs like that. or start sometimes or start and smoke a lil when start. i dont want to do valve job so if anyone knows a way fix this wo doing valves but no one seems to be able have answer here Quote Link to comment Share on other sites More sharing options...
eds92sc Posted September 4, 2008 Share Posted September 4, 2008 Didn't we talk about this start-up issue on a different post? I remember mentioning the timing belt, the spark plugs and wires, and the other person was afraid the ECU would have been the problem. Is that you? Yes that was me, I am still having the same issues, I am expecting a new crank position sensor today, and i'm replacing the IAC valve as well, from a 90 LS400 that was wrecked last week. as soon as I get those replaced I will be checking the timing, the timing belt and water pump are 4 months old, so I hope I can get this done. If anybody has an more suggestions please don't hesitate. thanks Tonyw, Did you get your car fixed when you changed out the IAC valve? My car had similar problems as yours. I changed the fuel ECU, the fuel filter, ran Seafoam through the gas tank, and have been filling up on Chevron Supreme with Techron. So far for the past few months, I have been able to start my car each time. However, it is a little odd, but my first start sometimes acts likes it almost won't start but when I let go of the start switch the eng catches and runs without any further problems. All subsequent starts are normal. Haven't been able to figure it out, but since it runs fine I haven't thrown any more money into the car. Been thinking it was the cold start injector or circuit, just a guess. For history purposes, my car snapped a timing belt, so I had the timing belt, water pump, plugs, wires, caps, and rotors replaced at the same time. Then the problems started. The car wouldn't start like it used to...... and the rest is what I just mentioned in the earlier paragraph. Quote Link to comment Share on other sites More sharing options...
tonyw Posted September 4, 2008 Share Posted September 4, 2008 Didn't we talk about this start-up issue on a different post? I remember mentioning the timing belt, the spark plugs and wires, and the other person was afraid the ECU would have been the problem. Is that you? Yes that was me, I am still having the same issues, I am expecting a new crank position sensor today, and i'm replacing the IAC valve as well, from a 90 LS400 that was wrecked last week. as soon as I get those replaced I will be checking the timing, the timing belt and water pump are 4 months old, so I hope I can get this done. If anybody has an more suggestions please don't hesitate. thanks Tonyw, Did you get your car fixed when you changed out the IAC valve? My car had similar problems as yours. I changed the fuel ECU, the fuel filter, ran Seafoam through the gas tank, and have been filling up on Chevron Supreme with Techron. So far for the past few months, I have been able to start my car each time. However, it is a little odd, but my first start sometimes acts likes it almost won't start but when I let go of the start switch the eng catches and runs without any further problems. All subsequent starts are normal. Haven't been able to figure it out, but since it runs fine I haven't thrown any more money into the car. Been thinking it was the cold start injector or circuit, just a guess. For history purposes, my car snapped a timing belt, so I had the timing belt, water pump, plugs, wires, caps, and rotors replaced at the same time. Then the problems started. The car wouldn't start like it used to...... and the rest is what I just mentioned in the earlier paragraph. No I have not gotten mine fixed, I can't fiure it out, with a fresh battery in and on the first crank it seems like it wants to start, it turns over runs for second then dies. I don't know. Quote Link to comment Share on other sites More sharing options...
eds92sc Posted September 4, 2008 Share Posted September 4, 2008 Didn't we talk about this start-up issue on a different post? I remember mentioning the timing belt, the spark plugs and wires, and the other person was afraid the ECU would have been the problem. Is that you? Yes that was me, I am still having the same issues, I am expecting a new crank position sensor today, and i'm replacing the IAC valve as well, from a 90 LS400 that was wrecked last week. as soon as I get those replaced I will be checking the timing, the timing belt and water pump are 4 months old, so I hope I can get this done. If anybody has an more suggestions please don't hesitate. thanks Tonyw, Did you get your car fixed when you changed out the IAC valve? My car had similar problems as yours. I changed the fuel ECU, the fuel filter, ran Seafoam through the gas tank, and have been filling up on Chevron Supreme with Techron. So far for the past few months, I have been able to start my car each time. However, it is a little odd, but my first start sometimes acts likes it almost won't start but when I let go of the start switch the eng catches and runs without any further problems. All subsequent starts are normal. Haven't been able to figure it out, but since it runs fine I haven't thrown any more money into the car. Been thinking it was the cold start injector or circuit, just a guess. For history purposes, my car snapped a timing belt, so I had the timing belt, water pump, plugs, wires, caps, and rotors replaced at the same time. Then the problems started. The car wouldn't start like it used to...... and the rest is what I just mentioned in the earlier paragraph. No I have not gotten mine fixed, I can't fiure it out, with a fresh battery in and on the first crank it seems like it wants to start, it turns over runs for second then dies. I don't know. I forgot to mention I threw in a new battery and new terminal lugs as well. Good luck on your motor. I understand how frustrating it must be after throwing all that money into a car that won't run. Keep the faith, and I hope you weren't affected too much by Gustav. Quote Link to comment Share on other sites More sharing options...
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