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Matt, Engineer
Category: Lexus
Satisfied Customers: 21726
Experience:  Honors degree in Mechanical Engineering, worked 8 years as a Formula 1 engine engineer.
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2000 ls400 started bucking at speed. stopped safely and

Customer Question

2000 ls400 started bucking at speed. stopped safely and turned off engine. restarted, ran rough and died never to restart again.
JA: Will the headlights turn on? Is the battery fully charged?
Customer: full charge.
JA: What is the model of your '00 Lexus?
Customer: ls400
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: starter fluid starts it.
JA: Anything else you want the mechanic to know before I connect you?
Customer: have had VSC issues intermittently, flashing of dash cluster, usually resolved by battery change after recharge. This time no go. had it towed 95 miles (ouch).
Submitted: 9 months ago.
Category: Lexus
Expert:  Matt replied 9 months ago.


I'm assuming that you don't have any check engine lights on and this sounds like a lack of fuel and could be a lack of fuel pressure from the electrical pump at the tank.

1st thing to try is to remove the fuel filler cap and then flick the ignition on whilst listening for the brief ‘buzz’ of the pump

If the connections to the pump are corroded or damaged then the pump could stop at any time or could not be running at full speed. Check that its relay switches in and out and the relay contacts are clean and bright – replace the relay if in any doubt and do the same for the fuse,

Ideally measure the pressure at the injector rail (should usually be around 3Bar / 45psi +) and if this is low check the pump as described and also consider changing the fuel filter as if this partially blocked this too will reduce pressure.

You can also get this issue with contaminated fuel , if there’s water or dirt in the tank then either the petrol floats on top of the water or the filter sock on the pump is choked up – so if the other things check out then I’d consider pulling out the fuel pump and cleaning the filter sock

Expert:  Matt replied 9 months ago.


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