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Issues With '98 Lexus Ls400


joncurry94
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Just recently bought a 1998 Lexus LS400 from my uncle at 238,xxx miles (has been passed down and taken good care of by family). Three days ago I was driving home on the interstate with cruise control going about 70 mph (full tank of gas) when the car started to sort of sputter. By sputter, I mean I felt the car jolt forward abruptly, and then feel as if it was slowing down. It kept doing this even out of cruise. Eventually, my RPMS read under 2,000 and I began to lose speed on the interstate. I had to push the pedal all the way to the floor to get any acceleration, this lasted for a few prompt minutes before it no longer worked, and I just consistently lost speed until I was able to pull over to the side of the road. In doing so, I was unable to accelerate anymore. I shut off the car, and restarted it, battery light came on. I was able to take off and make it to my subdivison before it did the same thing, except this time turning over but not starting back up. I tried several times, and the battery never did die. Two days later I try to start it to load it up on a trailer, and it starts fine. I take it to a guy who knows a bit more about cars than I do, and he has it sit and idle for 2-3 hours. The car doesn't shut down. He suggested the possibility of water getting into the gas tank, or possibly needing to replace the fuel pump and/or filter. I drove it back home, and it began doing the same things on the interstate, now it is dead again.

So I am completely oblivious when it comes to the subject of cars, does anyone happen to have any speculation or insight, perhaps guidance on what I should be looking at?

Car also has an engine light, I tried to check it out and it didn't come up with a code. I'm going to go back out in the morning and try to get it started, I was suggested by an ex Toyota/Lexus mechanic to buy the chemical by HEET to remove water from the gas and put it in.

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With the issues that are happening with the engine - I really think that there should be codes stored that would at least give an idea of what is or was going on. The check engine light... has it illuminated ever? If it has - a competent mechanic with a Toyota or Lexus ODB II reader can obtain those codes. For my wife's 1998 LS400 - I purchased one ($$$$) and it has paid for itself many times in helping me diagnose issues. I suggest to not just start "trying" quick fixes - rather take the approach that it does have an issue with fuel delivery and start troubleshooting via the codes. Since you say you are definitely not an automobile mechanic - I would suggest to take the car to a shop and ask for a diagnostic review - some shops charge a small fee to offer a diagnosis which they should deduct from the repair bill if you have them do the work. The codes should be there to be read and help understand what is going on.

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Welcome to the Lexus Owners Club, Jon!

I agree with Freddie...get the code(s) first then go from there. It will take a lot of the speculation out of the picture. With 238k miles, there are a number of things it could be. Rarely is the problem with "bad gasoline". We all would like to think it were that simple, but it almost never is. If your uncle still has maintenance records, you should try to get those from him.

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I agree with above posts. Unless you are ready to learn how to, and to spend way more than having a good diagnostic done to it.

You will need a GOOD scan tool not a code reader they can be got used in the 200 to 300 or so range and new into the 3000 to 4000 range. Also you will need factory service manuals, you can go to the dealer to study theirs if you can't purchase them.

With an intermittent problem like yours it is super difficult to diagnose and even taking it some place they may not find the problem. Just make sure they don't do repairs till they talk to you and you say yes or no to them and get that in writing up front.

With a problem like you describe and if it was my car here is the very first thing I would suspect if it didn't show a problem on a scan tool, http://www.clublexus.com/forums/ls400/656360-all-my-crazy-lexus-issues-solved-ecu-leaking-capacitor.html

and yes I would sample the gas to rule out that too. But before removing and checking the ecu I would do normal diagnostic things like checking fuel pressure and ignition system etc. such things as the igniter-s can cause problems you describe, and so could a failing crank or cam position sensor, or even a relay, there are lots of them in these cars. But the slow power down would be more of a fuel delivery type problem. If your car has a fuel pump resistor like the 1st gens do maybe its that. And even the pump it self.

If it would die and stay that way the problem is much easier to find.

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Jon, with codes p0171 and p0420, you may have an exhaust leak. It is somewhat common to get pinhole leaks in the exhaust header pipe which really messes with the fuel mixture. Or it could be a faulty O2 sensor(s). I do not think this 100% explains your cars poor performance and sudden loss of power however.

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