LS - 1st and 2nd Gen (1990-2000) Discussion topics related to the 1990 - 2000 Lexus LS400

97 Ls400 RPMs spiking and evening out (solved)

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Old 05-05-18 | 01:46 PM
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Default 97 Ls400 RPMs spiking and evening out (solved)

So just sometimes when I go to start my Ls the rpms will spike then even out to the normal idle position after just about two minutes of spiking and dropping. It hits just over 2k and drops around 1k. After this it’ll settle down below 1k. The car when running runs great and there’s no problem when driving it. Could this be just a TPS going bad??

Last edited by RA40; 05-18-18 at 12:27 PM. Reason: merged threads
Old 05-18-18 | 11:25 AM
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Default SOLVED!!! Bucking/Surging and power loss in 1997 ls400

so a few weeks ago I was driving my normal route to the gym and school (about a 25 minute drive). All of a sudden my speedometer drops and starts going everywhere, then my rpms drop to zero and spike up and lights on the dash begin to flicker and my car stalls. So I did research and decided to start with my IAC and so I replaced the whole part went to test drive it and in almost the same exact spot the car bucked and surged and struggled to recover power but stalled. So this is where I fixed it. I took apart the whole intake up to the throttle body. I found out I had a K&S airfilter from the previous owner so I immediately ordered a new one cleaned my MAF sensor and found out I also am missing a bracket for the MAF so right now I have it tapped super tight with electrical tape until the new bracket comes in. The next day I got my new filter and put everything back together nice and tight drove it to Gym and school and back through another small town another 15 miles away back home, parked it washed it then a hour later took another 45 minute trip in the other direction and still no problem. The K&S air filters are known to gunk up MAFs. Looking back the symptoms completely where like the car was being choked out and not getting enough air. The filter was disgusting by the way. So before you read how many things it could be just check you’re filter and clean MAF first before buying parts you don’t even know will work. When my bracket comes in I’m going to clean by throttle body too! And make sure to use special MAF cleaner!!! I’ll keep you guys posted if anything changes or if you have any questions👍🏼
Old 05-18-18 | 12:26 PM
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Glad that was an easy fix.
Old 05-18-18 | 02:49 PM
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They probably oiled the filter on both sides like a stupid person. I've used K&N filters for many 10s of thousands of miles on my LS and had no Issues.
Old 05-19-18 | 07:14 AM
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Originally Posted by Losiracer2
They probably oiled the filter on both sides like a stupid person. I've used K&N filters for many 10s of thousands of miles on my LS and had no Issues.
yeah probably, I’m just glad it’s fixed!!
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spuds (05-20-18)
Old 05-20-18 | 10:43 AM
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Brandon,what was the exact MAF cleaner you used so I can add it to my records?
Old 05-22-18 | 05:49 AM
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Any over the counter MAF cleaner will do. Had a similar problem with my 98, fluctuating RPMs at idle and the car would want to stall when coming to a stop.... just spray it more than you think you should and that should fix the problem.
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spuds (05-22-18)
Old 05-22-18 | 05:00 PM
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Thanks Legender,filed away for future reference.
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