BananaGS

FYI:
do not try to change the TPS yourself. you need to recalibrate it after you install a new unit. so if you don't know what you are doing, don't mess with it or get someone who know.

you should have a check engine light if the TPS is not functional properly, the ECU should already log an error on TPS . once the TPS is not functional properly , first sign of problem is rough idle, which you already know.

MAP sensor can also cause engine dying or rough idle, so is dirty injector or fuel

Anh

power3dfx

i want to share an experience ive had on my gs4 at idle. there has been two times that ive had the idle fluctuate, as if the car was going to turn off. the first time, i just sat there and watched, after about 5 seconds, i put my foot on the gas to start moving again, and the car turned off on me
the second time, the rpm would drop and rise below average idle rpm. this time i didnt let it continue, shifted from D to N, so that it would idle normally.
these two times that i have had this problem was after flooring it till about 60 and then come to a complete stop right after.
any ideas on why something like this happened??

BananaGS

your TPS is on the way out
or your MAP sensor in on the way out (most expensive to replace)

or there is a loose wire somewhere from the MAP sensor to the ECU

both can cause engine idles weirdly and dies

if I was you, i will wait til it happen again, usually, the ECU check engine light should come on when your engine dies for no reason.

anh

whitels

For the benefit of other GS owners in the future should this "rough idling" issue become a reality to them, I have wrote Lexus corporate this morning suggesting that they issue a bulletin/memo to dealers about the TPS replacement situation.

I hope that raising the dealers' awareness of this problem will be in the interest of everyone's time, both the dealers' and owners', by avoiding multiple time-wasting attempts to fix a known problem and foregoing exhausting long arguments with the SAs.

Manaray

Just a note, dirty/bad spark plugs can cause idle surges also...just FYI...

whitels

Tony, BIG THANKS. I'll keep this info in my leather bound Lexus Owners Manual.

Alewifebp

Thanks for the info. I've been having a rough idle for a few months now. SA said it was the reformulated gasoline. They of course also said no error codes showed on the ECU.

Question: Do you think that replacing this might also help the problem with engine ping on accelleration (which was discussed in deptch a few months ago)?

Tony

My engine never pinged before the rough idle. You might indeed have a engine problem perhaps new spark plugs would help out more then the TPS. Also try to pull the #39 fuse and then reset the ECU by disconnecting the battery for 20 minutes, other GS guys I talked to said it helped.

miko400

Yeah, this is some good information. My Gs idle pretty darn rough. Thanks I will check with my dealer...

GSquicksilver

hello all,

question: for those who have had their TPS replaced for the rough idling issue, how has your car idled so far? so far so good? i'm gonna take my car in pretty soon for this issue and i hope it'll be covered under warranty.

how long did it take for the dealer to fix this problem?

and to whitels, did you ever get a response from lexus after writing to them about this issue?

whitels

Lexus' response was by-the-book in nature, as if it was an attorney replying to me. Here's the full text of the response:

"If you are experiencing rough idling, please contact your Lexus dealership to schedule an appointment to have the vehicle inspected. If necessary, the dealership can order you a throttle positioning sensor for your vehicle. I am sorry for any inconvenience this situation has caused you."

No mention if Lexus dealers were advised of the TPS issue as I requested originally.

I guess, you'll find out. Bring a copy of this entire thread and get them to read it.

Would you please come back here after your TPS repair and report on what happened? Thanks.

miko400

Thanks for the update keep us informed. I also talked to my Dealer they wanted to know who told me changed TPS sensor....