Piston Slap: In Search Of...TPS Reports

Sajeev Mehta
by Sajeev Mehta
piston slap in search of tps reports

Reid writes:

My 1995 Lexus LS 400 needed a replacement computer to fix a known drivability problem related to the car’s throttle position sensor (TPS). Ever since I got the computer back, my car dies at low idle. I’ve reproduced it with the AC on, turning the AC off and then coming to a stop: it almost always stalls from its low idle.

When I originally had the computer checked out at a Lexus dealership, they said I might need to adjust the TPS after installing the new computer. I imagine that is what is going on, especially since the original codes from the (now replaced) computer said it was the TPS and I replaced it with a new one. Do you know if TPS adjustment is an easy fix that my mechanic can do?

Sajeev answers:

Mmm, yeah . . . I got the memo to TPS reports.

I think you are on the right track, those signs point to a TPS that’s out of whack. Judging by http://www.lexls.com/tutorials/EFI/tps.html">this link, this problem is easy to resolve with a multimeter and some other basic tools.

Long story short, your mechanic can recalibrate the TPS with no problems, but I’m a little surprised this is necessary.

[Send your car queries to mehta@ttac.com]

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4 of 17 comments
  • The pie plates from the SC430 don't look half bad with the drop.

  • Sajeev Mehta Sajeev Mehta on Apr 28, 2009

    So I'm gonna guess I got the TPS diagnosis about right. Please resume your Office Space related commentary. Thank you.

  • on Apr 28, 2009

    D---, why didn't I notice this post sooner; all of the good references are taken. "Well, that does it; I guess I'll just have to burn the place down."

  • Petrol42 Petrol42 on Apr 28, 2009

    I had this same problem with my Acura Integra. I know that my car isn't in the same league as the luxurious Lexus LS 400 but I'm assuming that the Lexus still has a throttle body. I was able to fix the problem by raising the idle by turning a screw on the throttle body. The problem with my car was that it was idling too low and not enabling the alternator to do its job. When my battery was finally low enough on juice, my car couldn't pull electricity from anywhere else and would die. What I might suggest if you don't mind getting your hands dirty is to scour the interned for Lexus message boards and post a question about how to raise the idle. The dirty part comes in when you have to rip off the plastic cover that hides your engine which I'd imagine by now is filthy under that thing. Anyways, the process literally takes 5 minutes and it saves you a trip to the garage where the crooked mechanic is going to charge you for unneccessary repairs. btw, ALL mechanics are shady one way or another. One last thing, I'm no expert but I'm assuming the idle of an engine gets affected by the fuel system getting dirty and gummed up. Using a Top Tier gasoline is key in long engine life. My Integra is almost 12 years old with 183,000 miles on it. The engine runs as strong as the day I got it and its only used Top Tier gas all its life. (google Top Tier gas.) One thing you can do to try and clean up your fuel system is to use a product called Seafoam. Look it up on YouTube. I haven't tried it yet but I have a bottle that I'm going to use soon. I'm normally not a guy to use ANY additives in my car but I've heard nothing but good things about Seafoam and it even cleared up my friends Check Engine Light.