I had the same problem until I took out my EFI Fuse for about 20 minutes that's the # 38 Fuse, Since then (4 months) I have not had the problem, Try it then post your results. I dont know why that worked It just did.

 

I finally argued with my service rep at the dealership and got her to replace the TPS unit. Im driving a loaner car from them right now and will post the results of this repair. I hope you guys are right about the throttle position sensor being the culprit. She was not to happy with replacing it under warrantee stating she could get in trouble with head quarters because the part was not defective.

I will post tonight if it worked on fixing the rough idleling problem and we will put this issue to rest and help alot of Club lexus GS 400 owners if it works.

Tony

 

Thanks Navaz I will try to pull that fuse tonight when I get the car back from the dealer. Ill post before and after the fuse and with the new TPS unit replaced.

Tony

 

Navaz according to the manual fuse 39 is the EFI.

 

Tony, appreciate your keeping us posted. This thing happened to me twice also. It has not happened yet since I removed the battery for quite a bit of time but there are serious indications elsewhere in CL that the TPS is the culprit. Since mine is out of warranty, my Lexus SA somewhat agreed that the TPS may have something to do with it (the SA didn't even argue, in fact was very sympathetic and tried his best to encourage me to leave the car overnight for them to diagnose but my schedule didn't permit it. The SA tried another day but again there's a schedule conflict from me). For a $75 fee, they will diagnose it and then apply the fee to repairs if needed.

Let us know what happened after the TPS replacement. It may be a while before you really see if the problem will come back.

 

Sorry, I ment # 39 fuse hit the wrong key.

 

Hey guys I just got my car back from the dealership 4/26/02 at 7:00PM they replaced the TPS unit and the car runs like its brand new. No shaking!!!!!!!!!!!!! In fact it was so smooth at idle I had to make sure the engine was on. Now thats how a Lexus should idle! Anyways for all GS owners experiencing rough idle insist on replacing the TPS units. The dealership will not want to do it but absolutely insist on it in writing like I did. They replaced mine under warranty and as a "Goodwill Gesture" use that phrase in the letter and stress to them that you are a loyal customer. The part is only 13 dollars and labor is 50 bucks. So if you cant get them to replace it because they dont want to replace it until it breaks or until the ECU reports problems. The ECU however will not detect a malfunction TPS. My technician even stated that he did not want to replace the TPS unit and said that it was normal for the car to idle rough. I told him just do it and now he is kissing my ***. They have tons of reports of GS ideling rough and could not figure out why so now they are happy mine is fixed so they can start helping others.

By the way the new idling rpm is 600-625 with the gear in drive and no AC. Absolutely no shaking. It makes me want to drive the car again and again to test it. I have a new love for my car again.

I have not tried pulling the #39 fuse like someone suggested if you guys tried that and it fixes the ideling problems to let me know. Mine is working so good I dont want to mess with it. So please post your results for everyone to see. I can sure vouch for the TPS being replaced.

Mystry is solved good luck guys.

Tony

 

Glad your problem was fixed, you see I had that problem also, so that's why I said to change the TPS. I must have taken my car to the dealership about 7 times before they found the problem, atleast now others don't have to go through the fustration that I went through...

Aloha

 

I've only experienced rough idle at cold start, and then, only when car is NOT in gear. I'd think that a rough idle would, at the least, be an emissions control issue. Would seem difficult to achieve LEV or ULEV status with rough idle. My SA also has mentioned it as common problem with the 4.3 L motor, but no TSB or recall to this point.

 

Thanks Itsallgood I remembered you saying you had to make multiple trips to the dealership so I wrote it down and referenced our forums. I think thats what made the SA get worried and replaced the TPS for me on the first visit.

Tony

 

Mooretorque, I have the same problem as you too. My GS only idles rough when I put it in neutral or in park.

Tony, this is very informative thanks a lot.

 

my car does the same thing.. it doesn't shake all the time though but sometimes you can feel it shakes a little bit ..

 

well i had my tps replaced about 3 months ago. BUT just yesterday my car stalled again!!! so either they gave me a faulty part or.. who knows! i have a SRT intake now so im scared to bring it back to lexus. im SURE they will say.. well we fixed it before.. and now u have that intake so thats the problem.. EVEN though hte problem existed before i had the intake! any suggestions??? thanks!

T