Lex 400 Posted July 27, 2005 Share Posted July 27, 2005 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. Quote Link to comment Share on other sites More sharing options...
Hampton Posted July 27, 2005 Share Posted July 27, 2005 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. Quote Link to comment Share on other sites More sharing options...
obergc Posted July 28, 2005 Share Posted July 28, 2005 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. Quote Link to comment Share on other sites More sharing options...
sha4000 Posted July 28, 2005 Share Posted July 28, 2005 probaby need a tuneup Quote Link to comment Share on other sites More sharing options...
nc211 Posted July 28, 2005 Share Posted July 28, 2005 Hate to say it....but it's probably the ecu unit. Is it a 95 LS400 or 96? Quote Link to comment Share on other sites More sharing options...
Hampton Posted July 28, 2005 Share Posted July 28, 2005 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. ← Oil strainer cleaned, what a mess work! ride seems fine than before but no big different, Quote Link to comment Share on other sites More sharing options...
VBdenny Posted July 30, 2005 Share Posted July 30, 2005 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. Quote Link to comment Share on other sites More sharing options...
Ca LS400 Posted July 30, 2005 Share Posted July 30, 2005 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. Quote Link to comment Share on other sites More sharing options...
Lex 400 Posted August 2, 2005 Author Share Posted August 2, 2005 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. Quote Link to comment Share on other sites More sharing options...
Ca LS400 Posted August 3, 2005 Share Posted August 3, 2005 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. ← Quote Link to comment Share on other sites More sharing options...
sha4000 Posted August 3, 2005 Share Posted August 3, 2005 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. ← a tune-up usually means new wires and plugs plus air and fuel filter Quote Link to comment Share on other sites More sharing options...
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