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wanttogofast

1992 Ls 400 Running Rough

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bought a 1992 LS400 has 285,000 miles check engine light has been on since i bought it had it diagnosed computer read tps sensor fault and egr valve fault. car was running great till an hour or so ago now it idles at 800 and runs rough revs up extreamly slow. says tps sensors were replace in 09 but when we unplug the tps sensors it has no effect on the way the car runs. any help is appreciated thanks.

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Don't lose the faith, You will have the LS running perfect in no time wink.gif Welcome to the clubcheers.gif

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well i bought the tps sensors thanks for the great help probally a waste of money but well see

Well TPS might be faulty but not the reason for your erratic idle. It could be you have a couple of things going on.

Sounds like a classic case of dirty throttle body and or dirty and sticking IACV. I'd try cleaning both of those as a starting point. Its a good maintenance item so even if you have more to do this won't be a wasted effort.

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If the EGR valve is stuck fully open it can give the problems you describe, is there excessive smoke coming from the exhausts? I know you have checked the coils but have you checked the distibutor caps and rotor arms?

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Tap on the EGR valve and see if it changes. Like Steve said, they can stick. the valve should be fully closed at idle, otherwise its like a huge vacuum leak, and will cause rough idle conditions

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How hard is it to Replace the EGR Valve?

I have a similar problem too. Car has rough idle,I can smell Gas and it vibrates on park and drive mode..

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bought a 1992 LS400 has 285,000 miles check engine light has been on since i bought it had it diagnosed computer read tps sensor fault and egr valve fault. car was running great till an hour or so ago now it idles at 800 and runs rough revs up extreamly slow. says tps sensors were replace in 09 but when we unplug the tps sensors it has no effect on the way the car runs. any help is appreciated thanks.

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Have you tried checking the fuel pump resistor. You can by-pass the resistor by jumping the connector and see if your problem goes away. The fuel pump is located on the right wheel well behind the air-filter assembly.

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