I have an 2004 SC430. It has throttle lag on take off. My SC feels like it is trying to down shift when it is already in first gear. I have been following posts on this site for years. I have not found a cure yet. If there is a cure please post it. I have had an 02 LS430, 04 LS430 and now a 10 Ls460 and none have lagged like the SC. My 02 LS340 I think has pretty much the same trans ,engine and probably the same computer system. Has any one tried to flash the SC's computer with the 02 LS430 programming? Is the LS computer compatible with SC? Can they be swapped out? I have tried all of the unsuccessful fixes, MAF, throttle position sensor, PCV, injector cleaner, sparkplugs and cleaning the throttle body, still runs the same. I hate being dusted by RIO at a traffic light. Come on guys, what is the fix?

 

I think the throttle reset would be my first attempt to change the way your car drives.

It is super simple and only takes like 15 seconds. However, I don't remember the procedure, so I just disconnect the battery for a couple of minutes.

 

The best way is with a Pedal Commander or similar device. Reset your ecu of course but you should not be so slow off the line even without this.

 

I do the reset. I hold the accelerator down a minute or two. Usually won't start on first try. Must forget crank position. Occasionally get a good take off after reset then back to lag. I have to try to stay out of situations that require a quick response.

 

I'm not having good luck with finding symptoms, but could the valve that controls intake manifold runner length be failing and this cause such a problem?

No idea if it could, but based on what the OP has already tried, I can't think of anything else.

And just to be sure - OP - are you sure the replacement throttle position sensor was installed correctly? I screwed up once on a Subaru and it took me a while to realize I forgot to rotate it the proper amount on installation.

 

Yes, I would look at and test the intake air control valve and associated components of this system.

I would also look at the camshaft timing control valve and the purge VSV in the EVAP system which can stick open and cause vacuum issues, or any other hose or component that could cause a vacuum leak. Check all ducts and hoses in the air-intake system for leaks, as well.

 

this should help…
https://www.clublexus.com/forums/sc4...ml#post9765688

 

MAF sensor was cleaned and then replaced. Checked TPS today still reads 12.5 throttle closed and 79.8 with throttle wide open. Slowly opened throttle digital and graph did not show anything erratic. Sprayed starter around and didn't get any rise in rpms. Surge in power over 4000 rpms runner length change or vvt kicking in. I'll pull the throttle body and see if the runner length mechanism works.

 

i guess the throttle reset does nothing…wish I was more help :-(

 

Is that (bolded text) with you holding the throttle valve fully closed? The FSM for 2002 is confusing (to me anyway) on the topic. As a result, not sure this will help, but in case you don't have the FSM...

In the Diagnostics section it lists good values as: Throttle valve fully closed: 7 − 11 % Throttle valve fully open: 65 − 75 %

In the Engine Control section it addresses installation measurements and states:

After turning the ignition switch ON, do not depress the accelerator pedal.
(h) While reading the valve of the throttle valve opening percentage (THROTTLE POS) of the CURRENT DATA, turn the throttle position sensor slowly to left and right and set the sensor at the center value of the standard value, and then tighten the screws. Standard throttle valve opening percentage: 15.6 − 19.6 %
(i) Recheck throttle valve opening percentage.

It then goes on to say :

(j) Perform fully closed throttle valve by hand and check that the valve of the throttle valve opening percentage (THROTTLE POS) of the CURRENT DATA stays with the standard value. Standard throttle valve opening percentage: 10 − 14 %
If the throttle valve opening percentage is not as specified, repeat steps (h) to (j).
(k) Paint the 2 set screws.

 

I changed TPS last year and went through the setup procedure then. I didn't see any reason to go the initial steps again. The final readings are in spec. The the graph and digital readouts are smooth indicating no dead spots. That was my main concern. Looks to me TPS is good.

 

OK, didn't realize you went through the whole process before - agreed no need to do it again. Thanks for clarifying.

 

How about ECU remapping?
A few of us have done that, and it is more fun to drive now

 

Remapping sounds good. If the SC430 would perform like my old LS430 I would me thrilled. Same engine transmission configuration. What version did you use, who did it and what was the cost?

 

https://www.clublexus.com/forums/sc4...uestion-7.html
Start at post #95, and quickly skim through the rest.
We all spent about $300 or so, you can send in your ecu or purchase one from them. I sent mine in but other prefer to purchase to get it quicker.