93ls400walt Posted June 25, 2006 Share Posted June 25, 2006 MY 93 Ls with 101,000 miles started to lose power on acceleration under a load. Such as A/C on or going up even a small incline. Or would drop the RPM if I tried to accelerate to fast. The engine dosen't miss fire or make any noise except a puffing sound when this happens. Sort of like a sneeze. If I am under 2000rpm, the engine will drop and increase the rpm repeatedly untill I let off the gas pedel. If I am over 2200rpm the engine rpm will drop to around 1200-1500rpm and stay there untill I let off the gas pedal. In park or neutral, the engine rpm will go up to 6k plus. Smooth and easy. Also while driving the engine does fine if I only accelerate slowly. If I push the gas down as if to pass someone. The rpm drops far enough as to slow the car as if I'm braking. The problem slightly improved with two new coils. And denso Ird. plugs. I also replaced the under car fuel filter. I had replaced the wires, caps, rotors and plugs 8000 miles ago. I changed the plugs again because I used Bosch Platinum then. And have read about fouling prob's with them after 6K. The electrodes looked ok, but there was browinsh staining around the outside area above the tighting ring. Looked as if there was a leak of combustion gas. The engine is much more responsive and smooth. The problem is much less. But still there. After that long story. The code readout is code 41. The TPS and or ECM fault code, and or the tps wire harness. Before the Dealer call, I will replace the Tsp sensor. Anyone ever do this without removing the throttle body. If so, How did you connect your Ohm meter? Also, any info on checking or replacing the wire Harness? The protective cover on mine looks as to have been melted to expose the wires. And the coverings on two of the 4 wires look mangled and are stiff to the touch. I looked at lexls for the tps adj. by hand, with trial and error. But it dosen't make sense to me. The tps adj. seems to be for an opened/closed setting using an ohm meter. Regardless as to what the idle speed is. Lastly, Any thoughts on this problem other than the tps? 1 Quote Link to comment Share on other sites More sharing options...
mehullica Posted June 25, 2006 Share Posted June 25, 2006 You are on the right track. Put a .014" feeler gauge between the throttle lever and small stop screw on the thottle body. Where the throttle cables connect to the throttle body you'll see the small screw, usually has yellow paint on it. Once the feeler gauge is between the screw and lever connect an ohmmeter to the bottom 2 pins on the TPS. move the TPS until you lose continuity. Move the TPS back and forth a couple times slowly to find the "sweet spot" where it breaks continuity and tighten the set screws for the TPS. Clear the code and you're done. Quote Link to comment Share on other sites More sharing options...
Gumart1 Posted June 25, 2006 Share Posted June 25, 2006 Walt - You don't need to remove the throttle body for the replacement. I'm replacing my TPS sensor and was able to get some Ohmmeter readings and do the test/adjustment properly. I've gotten help from a few members here. I'll add some pics later, but I used micro alligator clips that I purchased at Radio Shack and attached them to the two correct leads on the sensor (IDL and E2 if I remember). There are the two leads on the sensor that are nearest the driver's side when the sensor is installed. Once the alligator clips were in place, I loosely installed the sensor, then I used 14 gauge electrical wire and slipped it into the opening in the alligator clips. I attached new alligator clips to the open wires, then attached my ohmeter leads right into these clips. Sounds complicated but it wasn't. It's a VERY tight fit and I found this method to work just fine to get good readings. Melhullica described it accurately except you want to use a .40 feeler gauge when installing the new sensor. Also, according to the shop manual, you turn the sensor clockwise until there is NO resistance, and then tighten it down. Melhullica - In your post you said that you turn the TPS until you lose continuity, not resistance. If that's true, that would mean I'd have a reading of infinity on my ohmmeter. Now the ironic thing is that I am stuck right now as I install my new sensor because that's exactly what's happening. I go from about 8 ohms of resistance and then I lose continuity suddenly as I turn the TPS. But this is contradictory to the shop manual test which says turn it until there is no resistance. Just wondering where you found your info and if it's correct. According to the service manual, once zero resistance is acheived you are supposed to insert a .85 feeler gauge and have no continuity (infinity) whereas with the .40 you do have continuity with zero resistance. Walt - I purchased my new TPS from Carey at Park Place Lexus (Newlexusparts.com) for about $75 shipped and it was the lowest price I can find. Also it was shipped within 24 hours. I'll get some pics added later. Quote Link to comment Share on other sites More sharing options...
93ls400walt Posted June 26, 2006 Author Share Posted June 26, 2006 Thank you both for your info. It is very helpfull. I will order a tps asap. And report my results. I am wondering what, If any, problems your cars were having? My check engine light never came on. I checked for codes because of the acceleration problem. Walt Quote Link to comment Share on other sites More sharing options...
mehullica Posted June 26, 2006 Share Posted June 26, 2006 The procedure I described is without removing the throttle body. All work done on the car. I learned the procedure from an Japanese engineer, it'd different from the repair manual. You want to lose conitinuity, not have .40 resistance. It will give the best off throttle response. Quote Link to comment Share on other sites More sharing options...
maniek_LS Posted June 27, 2006 Share Posted June 27, 2006 I looked at lexls for the tps adj. by hand, with trial and error. But it dosen't make sense to me. The tps adj. seems to be for an opened/closed setting using an ohm meter. Regardless as to what the idle speed is. Lastly, Any thoughts on this problem other than the tps? I did TPS adjustment 2 weeks ago. Here is my page with step by step 'How to' http://www.ls400.waw.pl/SetTPSonthecar/index.html If you have any questions - mail me. Regards, Mariusz Quote Link to comment Share on other sites More sharing options...
93ls400walt Posted July 4, 2006 Author Share Posted July 4, 2006 Well it's done. Thank you all for your advice. I truly could have not done this without it. I still have my acceleration problem. It is somewhat better though. I did find that I could set the adjustment with the .40 blade. But would not achieve the second reading after changing to the thicker blade. The reading did not change. So I saw the there was free play on the throttle plate from the set screw stop before the throttle plate would start to open. so I held the stop arm to the position to where the plate was just starting to open and adjusted the stop screw down to it. It was at least 4-5 mm off. So now the throttle response is GREATLY improved. And my orgional prob. is some better. I still have it. I guess I'll look at fuel pressure next. I have not cleaned the MAF. I have a spray can of electrical contact cleaner for cars. Does any one know if this is safe to use on the MAF wires/transisters ? My O2 sensors don't throw a code. But what kind of acceleration probs. can these cause ? Thanks, Walt Quote Link to comment Share on other sites More sharing options...
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