birdman Posted February 22, 2004 Share Posted February 22, 2004 I have a 1990 ls400 with 89,000 miles on it.Just had a full tuneup done.While driving between the speeds of 40 and 60 or so mph the car seems to sputterd and jerk like the motor is missing or trans is slipping.When I get around 70 or faster it seems to smooth out.I figured it wasn't the motor or it would do it all the time.Any suggestions would be helpful.Haven,t owned the car for about a few months and I'am already to sell it, if I can't figure this out.Thanks. Quote Link to comment Share on other sites More sharing options...
90LS400Lexus Posted March 1, 2004 Share Posted March 1, 2004 Have you tried new plug wires and/or plugs? My 90 LS400 had a miss at idle when I test drove it. I told the seller if they fixed the miss- I would buy it. Turned out that it was bad plug wires. Perhaps this is your problem? Good luck. Quote Link to comment Share on other sites More sharing options...
mapman Posted March 1, 2004 Share Posted March 1, 2004 I had similar thing happen several times with my 91. Turned out to be a little water in the gas. Every time i bought from certain station I would get just enough to cause a occasional miss. Quote Link to comment Share on other sites More sharing options...
UCF3 Posted March 1, 2004 Share Posted March 1, 2004 I have a 1990 ls400 with 89,000 miles on it.Just had a full tuneup done.While driving between the speeds of 40 and 60 or so mph the car seems to sputterd and jerk like the motor is missing or trans is slipping.When I get around 70 or faster it seems to smooth out.I figured it wasn't the motor or it would do it all the time.Any suggestions would be helpful.Haven,t owned the car for about a few months and I'am already to sell it, if I can't figure this out.Thanks. It sounds like someone hasn't tuned it correctly, or a bad wiring/plug. Perhaps you could take it back to the tuning company, and ask them to drive the car. Question did this problem happen before or after your tune-up? Quote Link to comment Share on other sites More sharing options...
BlackSC4 Posted March 1, 2004 Share Posted March 1, 2004 It happened to him after the tune-up. funny thing is, that's exactly what's happenning to me now. about 45mph it seems like the tranny is pulling back and pushing the gear in hard. this was also after i performed a complete tune up for my car as well. but i may have an idea as to why this is happening in my particular case... Quote Link to comment Share on other sites More sharing options...
birdman Posted March 2, 2004 Author Share Posted March 2, 2004 The car was doing this before and after tune up.I thought a tune up would have fixed this problem.Don't think its the motor.Just not sure. Quote Link to comment Share on other sites More sharing options...
big50daddy Posted March 5, 2004 Share Posted March 5, 2004 After long periods of highway driving does the car die when slowing down or coming to a stop? Quote Link to comment Share on other sites More sharing options...
birdman Posted March 6, 2004 Author Share Posted March 6, 2004 No it doesn't die or act up in anyway.You can feel a very lite jerk,studder,or maybe the engine slightly missing best about 45mph with the engine running about 1600rpm.Once you give it more gas to accelerate to 60 or above it goes away. Quote Link to comment Share on other sites More sharing options...
UCF3 Posted March 6, 2004 Share Posted March 6, 2004 It could be the fuel filter. Any error codes appearing on the diagnostic device? Quote Link to comment Share on other sites More sharing options...
90LS400Lexus Posted March 7, 2004 Share Posted March 7, 2004 Before I bought my 90- it had a miss at idle. He said they had just had it tuned up, but it still missed at idle. I told them I would check back after the miss was fixed. I called later and he said they took it back and it turned out being a loose plug wire that they did not properly attach. Quote Link to comment Share on other sites More sharing options...
splitslim Posted May 26, 2004 Share Posted May 26, 2004 Birdman, did you solve your problem? I am having the same issue now and am wondering what to do. Thanks, SS Quote Link to comment Share on other sites More sharing options...
ModMan Posted May 27, 2004 Share Posted May 27, 2004 A dirty EGR valve or a clogged EGR breather (attaches to the EGR valve) can cause the LS 400 to seem to hesitate between 40 and 45 mph. My 92 LS400 would hesitate at this speed range when it had about 150K on it. Taking the EGR valve off and cleaning it with carb cleaner fixed it. The EGR valve is easy to remove and re-install. I found the solution at this Site Later I had to take off the intake manifold off to clean the cold start injector (long cranking times) because the fumes which fouled up the EGR valve had completely covered the start injector with a black deposit. This task required a full day to accomplish. Quote Link to comment Share on other sites More sharing options...
splitslim Posted May 27, 2004 Share Posted May 27, 2004 ModMan, can you post the instructions on cleaning the EGR valve, I went to that site you left and was not able to find a solution. Thanks, SS Quote Link to comment Share on other sites More sharing options...
austinls Posted May 27, 2004 Share Posted May 27, 2004 I have a 1994 LS and had similar symptoms. After changing wires, plugs, cleaning the throttle body, etc., a mechanic friend of mine suggested it may be a transmission issue. Lexus has changed the recommended transmission fluid type since 1994, and he flushed the transmission and replaced the fluid with the new type, This helped tremendously with much smoother shifting...but I still had the hesitation. I took the car to Lexus and they ran the diagnostics and found an error code (I don't recall the number) that was causing the hesitation. They reset the computer and I have not had the problem since (2 years ago). Cost me about $50. Hope this helps. Quote Link to comment Share on other sites More sharing options...
austinls Posted May 27, 2004 Share Posted May 27, 2004 The error code I mentioned in the previous reply is: Code 31, "Air flow and ECM in fail safe mode", causing erratic shifting. Quote Link to comment Share on other sites More sharing options...
silvermate Posted May 27, 2004 Share Posted May 27, 2004 the EGR vaccum modulator is located almost on the top right of the engine, its to the left and up from the oil cap if you are looking at the engine straight on.. its a round black unit that has some hoses running through it to clean it you just take a flat head screwdriver and pop the black cap off, under the cap lies the filter, pop the filter off and clean the unit as well as the filter with a can of compressed air... if the filter is beyond cleaning just replace it.....the whole process takes very little time good luck :) Quote Link to comment Share on other sites More sharing options...
ModMan Posted May 28, 2004 Share Posted May 28, 2004 If cleaning the small air filter doesn't help, remove the EGR valve by loosening the 2 or 3 small bolts securing it to the intake manifold and clean the inside of the EGR valve with solvent. You will have to disconnect a few vacuum hose connections and unclip some vacuum components to gain access. Quote Link to comment Share on other sites More sharing options...
kazools400 Posted July 9, 2004 Share Posted July 9, 2004 Anyone know if the EGR valve is in the same place on a 93 LS400? "to the left and up from the oil cap" Quote Link to comment Share on other sites More sharing options...
FreddT Posted July 9, 2004 Share Posted July 9, 2004 I just replaced the wires on my '94LS, and had a very similar "miss" problem 2 days later when going over 20. Turned out the wire from one distributor was loose. Replaced it with the old wire, and the problem was solved. I doubt your situation is the same, but it sure sounds like you have an electrical problem. Quote Link to comment Share on other sites More sharing options...
OldSkool Posted July 9, 2004 Share Posted July 9, 2004 I have the same problem I just posted seperatly. Didn't catch this post in time I guess..sorry. I will try the EGR Valve and work my way through a tune up from there. Something has to fix this problem. I will post which part made a difference when I'm done. Quote Link to comment Share on other sites More sharing options...
kazools400 Posted August 6, 2004 Share Posted August 6, 2004 I changed my plug wires and it helped the hesitation i was experiencing but didn't stop it. Now, I've changed from 91 octane to 93 octane gas and the hesitation is completely gone. I have a hard time believing it was the gas but it seems to be. Quote Link to comment Share on other sites More sharing options...
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