Puzzled by problem! ('97 LS ECU Issue?)
12-25-11, 04:46 PM
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Puzzled by problem! ('97 LS ECU Issue?)
My daughters both drive lexus (97 ls400, 99 rx300) . We bought them because of the safety features even on these older models. I've had good success working on both. However, got a tough problem with the ls400. This is a fantastic car but has developed the problem of shutting off after about 20-30 minutes of driving. It will crank fine, idle great, run great but then lose power and shut off. It will not crank up immediately, but if you let it sit for 15+ minutes it will crank and run perfectly until it loses power again without warning. No vaccuum leaks, plugs and wires are fine and getting fuel okay. After reading forums have narrowed it down to probably ECU. Just want any more opinions before I shell out the money for rebuilt. I cannot think of what else it could be. Thanks for any help!
12-25-11, 07:29 PM
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Thanks for the welcome. I have really come to love these cars. Very well made. One thing, I have read about wiring harnesses failing in the trunk area causing them to die while driving. The car did die when I went over railroad tracks the other day. Had been running perfectly up to that point.
12-25-11, 07:55 PM
#5
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Thanks for the welcome. I have really come to love these cars. Very well made. One thing, I have read about wiring harnesses failing in the trunk area causing them to die while driving. The car did die when I went over railroad tracks the other day. Had been running perfectly up to that point.
12-25-11, 09:56 PM
#6
Nothing the OP has said even comes close to indicating a CAT issue....really
OP, the trunk harness issue was really only prevalent on 1st generation cars (89-94) but is worth looking at. Usually though that problem doesnt stop the car from running so much as making the body ecu go nuts.
hook the car up to a code reader, for all you know the light in the dash for the CEL could be burned out (does it turn on when you first put the key in the ignition?) If you can't retrieve codes at all then that's a pretty good indication of a bad ECU. pretty rare in the later model years (was a problem in '95/96 for stalling issues, but fixed mid-year '95 iirc)
12-26-11, 06:19 AM
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Thanks for input. The CEL light comes on when cranking and when it begins to lose power. But when it is running well, no light. It will occaisonally sputter or act very weird (dash lights come on, sounds very rough, and brakes get hard) for a second or two while driving but then smooths out and runs fine until it powers down. Of course, waiting about 15 min usually fixes the problem for a while.
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12-26-11, 06:23 AM
#8
If it were ignition related you would expect the CEL to be on indicating a fault but as there isn't have you considered a fuel related fault.
If the fuel pump has for example an intermittent fault when it gets warmed up it would cause all the symptoms you mention but would not produce a warning light.
Have the fuel rail pressure checked when the fault happens.
Having seen your latest post when you now mention the CEL does come on, have the stored codes read then go from there, a common cause of your problem could be down to the CPS as they often become thermally sensitive and fail when warm.
If you have access to "freezer spray" you could cool down the CPS when the fault occurs and then see if the engine fires back up normally again.
If the fuel pump has for example an intermittent fault when it gets warmed up it would cause all the symptoms you mention but would not produce a warning light.
Have the fuel rail pressure checked when the fault happens.
Having seen your latest post when you now mention the CEL does come on, have the stored codes read then go from there, a common cause of your problem could be down to the CPS as they often become thermally sensitive and fail when warm.
If you have access to "freezer spray" you could cool down the CPS when the fault occurs and then see if the engine fires back up normally again.
Last edited by steve2006; 12-26-11 at 06:27 AM.
12-26-11, 10:24 AM
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After letting it warm up (sounded a little rough at high idle) the rpms dropped down and it ran smoothly. I let it run until it got warm and then it choked down. It would not start right back up and sounded like it wasn't getting fuel. Plenty of battery power just sounded like no gas. How can I check the fuel pump? Thanks
12-26-11, 01:07 PM
#11
As I have already suggested have the fuel rail pressure checked either buy a a suitable pressure gauge or ask a local shop to check it for you when the car runs badly.
Another way to determine if the problem is fuel related is to spray some ether or easy start into the airbox while cranking the engine,if the engine then fires and runs better it would confirm a fuel problem.
You really need to find out if the problem is ignition related or fuel related this reduces the possible causes by at least 50%.
Again as the CEL comes on have you had the stored codes read?
Another way to determine if the problem is fuel related is to spray some ether or easy start into the airbox while cranking the engine,if the engine then fires and runs better it would confirm a fuel problem.
You really need to find out if the problem is ignition related or fuel related this reduces the possible causes by at least 50%.
Again as the CEL comes on have you had the stored codes read?
Last edited by steve2006; 12-26-11 at 01:11 PM.
12-26-11, 02:54 PM
#12
.
Nothing the OP has said even comes close to indicating a CAT issue....really
OP, the trunk harness issue was really only prevalent on 1st generation cars (89-94) but is worth looking at. Usually though that problem doesnt stop the car from running so much as making the body ecu go nuts.
hook the car up to a code reader, for all you know the light in the dash for the CEL could be burned out (does it turn on when you first put the key in the ignition?) If you can't retrieve codes at all then that's a pretty good indication of a bad ECU. pretty rare in the later model years (was a problem in '95/96 for stalling issues, but fixed mid-year '95 iirc)
12-26-11, 02:54 PM
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I tried to read the codes when the car shut off and would not crank . Reader is showing 0 codes. Is there a way to retrieve stored codes? Not the best mechanic on this end but this website has helped me with problems in the past. I'll try the ether. I've been working off and on on it all day. After it died earlier, tried to start it several more times and it will not start. Turning over but just not starting. I will try to check fuel pressure tomorrow. Thanks for you help
12-26-11, 03:45 PM
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Is the fuel pump for this model located in the trunk? That would probably be some bright spot in my trying to fix it. Haven't done too much exploring on this car because it has really had zero problems. Learning as I go. Does Chilton or Haynes put out a good manual for this car. Thanks