Colby

My damn car keeps stalling! The RPM's are way low, usually around 400 RPM. When decelerating rapidly, such as an offramp, the RPM's drop to about 200, and sometimes it'll build back up to 400-600, other times it'll drop to 0 and stall. Not cool! Turning on the A/C helps increase the RPM's, but it stalled again today even w/ the A/C on. Any ideas as to what the problem could be? I've heard of "shock lock" or "throttle off shock" in one thread, but can't find any more about it (yes, my car also has a thunk problem when decelerating..another sign of this "off throttle shock"). If there is a mechanical or sensor problem, obviously that needs to be addressed, but since it otherwise runs fine, is there any easy way to just increase the idle RPM?

Colby
'95 LS400

Losiho

Idle speed is set by the ECU and is not adjustable. You'll need to look at other areas for your low idle problem (eg, TPS, throttle body, MAF, carbon buildup, etc). The problem has been discussed here before, a search will help you out.

Pyrotech

My 95 LS does EXACTLY the same thing. Strange that your symptoms are ABSOLUTELY IDENTICAL to mine. I have noticed though that mine only does it after being on the highway for a time (maybe 10 minutes or more) and then when I decelerate the car is fine until it hits about 35mph at which time the rpms drop immediately to around 200. My lights dim as well but the car usually does not stall unless i shift it into Neutral at this point. When it is hotter outside, I do have the deceleration shudder that is quite common (I am finding) on this year/model. For the symptoms you describe, if the car does stall, it always turns right back on and the strange rpm symptoms are gone. Likewise, if I just turn the car off and then back on the symptoms go away as well! I just wish someone knew what the problem was. I've had the TPS replaced as well as a full tranny flush. There are just so many other things it could be. With about 125k on the odometer I think it's too early for this kind of mystery illness for the LS. Maybe someone with the 95 LS has had success with diagnosing and fixing this problem.

Jamie.

Colby

I would appreciate a link to this discussion. My search did not turn up anything but the thread mentioning the off throttle shock.

Colby

paradox

I've had the same thing happen on other cars, and it turned out to be the Idle Air Control Valve which needed changing....
...For the throttle off shock, VVT-i had provided some info awhile back. This was most pronounced in the early production '95 LS' . A TSB was issued, and the fix is a revised ECU, Cruise Control ECU and spark plugs to resolve. It's very expensive... My aftermarket warranty company refused to cover it. A relatively inexpensive compromise, I discovered, is an induction/top end cleaning for carbon buildup over time. I just had that done, and man, off shock is barely perceptible now - whereas before- sometimes it felt like my transmission doubled as a jackhammer. Because the ECU is so sensitive, the carbon buildup magnifies this effect exponentially.
If any Atlantans have this problem, need more info on this, or wanna have this or other Lex repairs done, the guy that did the procedure on my car is John Minozzi @ 770-552-5280 (http://www.ozzis.netfirms.com/). The man's a walking Lexus encyclopaedia, and does great work. (Plug time!!!)
Apologize for deviating, but for the original problem, I would include the IAC Valve in my suspect list...

kjbro

My 95 LS400 does the same thing and I have learned to live with it. I would say that it happens approximately 5% of the time, so I don't sweat it much. When I start the car up after such issue, car runs fine and RPM's are normal. I find that it happens most when slow deceleration from freeway to long offramp. The car is mostly coasting at this time and quietly dies at first stop. Again, it is consistent in the type of road condition (long/slow coast) and pretty infrequent. I do, however, share your frustration. I don't plan to have exploratory surgery with the Lexus folks to remedy. The annoyance does not outweigh the high cost for such service.

500amg

The strangest thing...our '95 LS400 did the SAME THING about 3 days ago. My father was driving (after about 1 hour on a state highway) and came to a stop at a red light. He said when the light turned green he hit the pedal and nothing...looked down and the car was off (can't fault the LS for being that quiet ). Later that evening my mother was driving and the same thing happened under similar circumstances (highway to red light).

This is the first time anything like this has ever happened. Do ya'll suppose that our problem is the same as that listed in this thread? Any other specific ideas besides the Idle Air Control Valve?

hyperopt

Why not test, and, if necessary fix, the ISC? If the ISC is still functional, the problem lies elsewhere.
My wife's LS idle speed acted up until it could nolonger hold idle speed with foot off pedal. I tested and rebuilt the ISC and that fixed the idle problem.

5ofakind

If anyone is interested in the procedure for checking the ISC Valave....please contact me & I can send you the procedure for on-car or off-car inspection.

Jeff

Colby

It appears the throttle shock issue (which causes the clunk off throttle) and the low RPM/stalling are two separate issues. Check out the following thread for all those suffering from low RPM/stalling:

https://www.clublexus.com/forums/sho...&highlight=isc

Colby

500amg

Thanks so much for the link; that sounds like the exact issue we had.