My Jerking Lex

[Lex 400]

My LS 400 starts jerking at about 40mph. It seems that the faster i go the harsher the jerking gets. the rmp needle goes down a couple hundred rpm and then back up to normal when it jerks. It also only jerks when my foot is on the gas pedel and moving down the road. If i let go of the gas pedal the jerking stops. The jerking seems to be a random because it does it whenever it feels like it. There are times when it is just fine. When i pull up to a stop light it seems to idle fine around 600 to 650. I would apreciate any ideas on tracking down the jerking.

[Hampton]

My 95ls400 has the same problem, I find there are four jerks I can feel slightly around 30mph,40mph,60mph,70mph if I don't keep gas pedal deeper. I am plan to clean the ATF strainer today or tomorrow if it helps. I will let you know.

[obergc]

I had similar symptoms with my 93 LS that went away after I put in a new Ignition wireset, a new set of plugs and new rotors and caps. I think I could have gotten by with just the wireset though, when I removed several of the wires from the sparkplug, the sparkplug wire separated and a portion of the wire stayed attached to the plug. Runs smooth as silk after replacing the ignition parts. That's the first place I would look for your problem.

[sha4000]

probaby need a tuneup

[nc211]

Hate to say it....but it's probably the ecu unit. Is it a 95 LS400 or 96?

[Hampton]

My 95ls400 has the same problem, I find there are four jerks I can feel slightly around 30mph,40mph,60mph,70mph if I don't keep gas pedal deeper. I am plan to clean the ATF strainer today or tomorrow if it helps. I will let you know.

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Oil strainer cleaned, what a mess work! ride seems fine than before but no big different,

[VBdenny]

Go out and night and start the car. Look under the hood at the spark plug wires. If they arc, you have a problem, sometimes you can even hear it. I'd take obergs advice first as he has a pretty good handle on these cars.

[Ca LS400]

Just purchased a '93 LS400 about 2 months ago. Within 2 weeks, same "jerking" problem occured. Thankfully was simply one of the ignition wires shorting out. New set of wires + 1 &1/2 hrs. labor, approx $300.00. Runs incredibly now ! I'd reccomend to anyone experiencing any "misfiring" issues to have wires checked 1st. Hope this helps.

[Lex 400]

Thanks for all the suggestions.

It is a 92 LS400 and i keep it properly maintained just had a tuneup and oil change 3 week ago. I will try a new wire set first it is pretty much the only thing i have not changed in a long time.

[Ca LS400]

Just purchased a '93 LS400 about 2 months ago. Within 2  weeks, same "jerking" problem occured. Thankfully was simply one of the ignition wires shorting out.  New set of wires + 1 &1/2 hrs. labor, approx $300.00. Runs incredibly now ! I'd reccomend to anyone experiencing any "misfiring" issues to have wires checked 1st. Hope this helps.

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[sha4000]

Thanks for all the suggestions.

It is a 92 LS400 and i keep it properly maintained just had a tuneup and oil change 3 week ago. I will try a new wire set first it is pretty much the only thing i have not changed in a long time.

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a tune-up usually means new wires and plugs plus air and fuel filter