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Help, My Ls400 Is Not Starting


EastWind

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My 91 LS400 is not starting, usually, when it's cold. It idles rough sometimes when I start it up. Sometimes the idle clears up, other times, it doesn't but will start up smooth if I leave it and try another time. The last time I started it, it was idling very rough and I just had the feeling it will not clear up, so I let it be. But since then, when I try to start it, it acts like it's about to start up, the rpm goes up and then drops to 0 and it shuts off. It doesn't even run for a second or 2 before cutting off. Any ideas what the deal is? :(

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Not much any of us can do from here. I am not one to throw parts at an engine and "hope for the best". A good shop will connect fuel pressure gauges and check pump output pressure, and use an ignition analyser to check for ignition performance, in the absence of a trouble code. Unless you have those tools and skills, get a good shop to look at it.

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My 91 LS400 is not starting, usually, when it's cold. It idles rough sometimes when I start it up. Sometimes the idle clears up, other times, it doesn't but will start up smooth if I leave it and try another time. The last time I started it, it was idling very rough and I just had the feeling it will not clear up, so I let it be. But since then, when I try to start it, it acts like it's about to start up, the rpm goes up and then drops to 0 and it shuts off. It doesn't even run for a second or 2 before cutting off. Any ideas what the deal is? :(

I believe the Gen-1 cars have an extra fuel injector that only functions for the warm-up cycle, and it could be that, if that's so, either the injector has failed, or the coolant temp sensor for the computer has failed. That or the wiring has opened up. Has the Check Engine Light come on? It sound to me that the engine is stumbling because it's too lean at low temperatures. I don't trust the CEL though. My car had the TPS switch fail twice, and the coolant sensor fail once, and in both cases nothing got picked up by diagnostics.

Hope this helps!

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