Csosz74 Posted June 3, 2010 Share Posted June 3, 2010 Hi everyone, my LS400 stutters when I try to hold 45-50mph. I just push the gas lightly to hold that speed and the car stutters. I guess this is the right term. I have no problem at higher or lower speeds, and it does not do when I floor it. I have a small leak at the back of the left side valve cover, can it cause this? Thanks A Quote Link to comment Share on other sites More sharing options...
steve2006 Posted June 3, 2010 Share Posted June 3, 2010 Hi, You don't state the year of your LS but even if there is no dash warning light for the engine management system I would read the fault codes to see if anything is coming up. The vacuum pipe does need attention but is unlikely to be the cause of the problem. The most probable cause is the TPS mounted on the throttle body,the electrical tracks in this do wear and the wear is normally at a constant cruising speed point. Symptoms of a Defective Throttle Position Sensor Following is a list of symptoms, either of or a combination of which, a car driver may experience because of a defective throttle position sensor: Bucking and jerking of the car Idle surging Sudden stalling of the car engine Hesitation while the driver of the car is trying to accelerate Sudden surge in car's speed while driving on the highway Quote Link to comment Share on other sites More sharing options...
Csosz74 Posted June 3, 2010 Author Share Posted June 3, 2010 Thanks very much. The car is from 1990 with 263K. I will take it to repair soon so will ask the mechanic to check the codes. A Quote Link to comment Share on other sites More sharing options...
Hanging In There Posted June 4, 2010 Share Posted June 4, 2010 Hi everyone, my LS400 stutters when I try to hold 45-50mph. I just push the gas lightly to hold that speed and the car stutters. I guess this is the right term. I have no problem at higher or lower speeds, and it does not do when I floor it. I have a small leak at the back of the left side valve cover, can it cause this? Thanks A A throttle valve cleaning might solve your problem. My vehicle had the same sounding issue that was corrected with a good cleaning of the throttle body. Quote Link to comment Share on other sites More sharing options...
Csosz74 Posted July 31, 2010 Author Share Posted July 31, 2010 Thanks for the replies. It turned out that the previous 'mechanic', who did the tune up didn't push the spark plug wires correctly, so they cracked, became wet, etc. so they needed a replacement, and also, he put cheap spark plugs instead of the right ones. Quote Link to comment Share on other sites More sharing options...
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