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obergc

1st Gen Throttle Body Cleaning

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Recently my LS400 developed a rough idle and a hesisitation or miss when driving at partial throttle like in city traffic. I performed an "on vehicle" throttlebody cleaning that has restored the normal smooth idle that I was used to. My 93 LS400 has 100K and I imagine that anyone who has a first gen LS with similar milage also has a throttlebody that is rather dirty that has been or will be causing similar problems. I put together a 26 slide power point presentation with photos showing the procedure for doing the cleaning that any moderate DIY'er can perform for about $2.00 worth of materials. The presentation is an approximately 1.5 meg download and you will need power point viewer installed on your computer to watch it. The powerpoint viewer is free at

http://www.microsoft.com/office/000/viewers.asp. If anyone is interested in receiving the power point presentation you can email me at obergc@cox.net and I will send it to you. This is not a difficult thing to do but anyone who uses the presentation assumes all responsibility for any damage to their car and for any injuries they might sustain while doing the procedure. The file is too large to attach to this message, and I don't know if there is any way that I could post it in the forum so that it would be available to all. Let me know if you are interested.

Curt

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I have a 1991 Lexus LS400 and it has a similar problem. I really don't know exactly where it is coming from. It has around 130k with a huge tune-up which includes new plug wires. The problem is: When you are driving around 45mph at light throttle it starts to glitch with a hesistation. It's not losing power,nor the fuel pump is low. It almost seems like the car is going out of o/d into 3rd and back into o/d but the tack (rpm) doesn't move at the hesistation. Going at full throttle and stomping on it works like a charm like it should. This problem only occurs at light throttle while cruising down the road. Could it be an O2 senser? or does the throttle body needs to be clean. I'm referring to curts message.

Paul

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My 92 does exactly the same thing Paul, although it is very slight. I think it is the transmission shifting. When I select third, it is much better or completely eliminated. I too have checked the throttle body and I found it as clean as new. No deposits at all.

An O2 sensor will produce a code if it fails - a pal of mine had that happen, and the diagnosis is quite simple at that point.

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When you checked the throttle body, did you open the aft throttle plate and check the backside of it as well as the bore behind the aft throttle plate, that is where the grime forms. If you just look down the throttle bore, it looks clean. My car had a LOT of goop built up behind the aft throttle plate, just a thought.

Curt

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