Hi everyone,

i own a lexus LS430 2006 model

i have this problem of slow response to accelaration.
im literally tired bcoz no garage is able to diagnose the problem. On the system check it doesn’t show any errors. I have changed the following things-
​​​​- gearbox
​​​- coils
- spark plugs
- cleaned the fuel injectors
​​​​​​- fuel system service

i fail to understand what seems to be the problem
its very annoying when you have to speed up and change lanes
put the foot down and it takes its own time to speed up

please help

 

Things are much easier when there is a check engine light, that is for sure..

So without much info asside from the symptom of slow acceleration there are many stab in the dark guesses (or combination of factors) to what the cause can be.

Such as failing fuel pump or partially blocked fuel filter, cracked vacuum hoses, dirty air filter, dirty or failing MAF sensor, faulty throttle position sensor, faulty accelerator pedal sensor, failing/faulty knock sensors, failing/faulty O2 sensors, clogged exhaust, sticking brakes failing ecu, low compression etc etc.

Sometimes electronic components can be faulty manifesting as poor acceleration or high fuel use without being bad enough to throw an engine code by being out of the computers tolerated range.

Now without just replacing parts adhoc and hoping, it would help to get some data to see what the computer sees.

Do you have, or have access to an obd reader like obdlink mx?

If so, then let's start with collecting some data so we can rule out a few things.

The other good place to start is by having a good close look at those vacuum hoses/tubes to make sure they are nice and flexible rather than old, hard as rocks and brittle, likely leaking amounts of unmetered air into the engine after years of engine heat under that engine cover. Refresh all of them if you find any hard and brittle. It's a good idea to replace the pcv and grommet seal at same time.

 

My solution was a clean MAF sensor. Use only CRC Mass Air Flow Sensor spray cleaner available at auto parts stores. Dramatic improvement. I do it every oil change and takes 5 minutes. If super dirty may have to replace MAF, go Denso brand instead of pricy dealer route.

Please report back.

 

I was about to post the same. Personally for the money I would just replace the MAF with a new one. Don't buy off eBay as they are known for have fake ones in Toyota/Lexus boxes. I got mine from RockAuto for about $70. I would also suggest you look on YouTube on how to remove/clean your Throttle Body and IAC port (be careful to try not to rip the gasket or buy one to replace it).

 

thanks for the detailed information
i did check on the vacuum pipes and had one replaced while cleaning the injectors
rest of the pipes look fine for now
i have cleaned the MAF sensor
feel some power but its strange that the speed reduces or feels stalled at gear shifts Then i have to accelerate further to speed up, if i dont put the foot down it seems like its losing speed

 

I used the CRC MAF cleaner today as you recommended. Feel there is some improvement. But the underlying problem hasnt improved much.
the speed seems to stall or reduce at gear shifts. Then i have to put the foot down

 

i have Used the CRC MAF cleaner today. Lets see how it performs. If thr is no significant improvement ill change the MAF sensor.

 

Do you have a reader that can data log?

Something like and obdlink mx and an app like car scanner on your phone?

With some data we will be in a much better situation to work out what is causing the problem. MAFs are a good place to start but they certainly are the only thing that can cause slow acceleration

 

Were you able to clean both pairs of fine wires within the MAF sensor? Look around the inside and will you find 2 separate sets of sensor wires. Missed this the 1st time I did the cleaning and after cleaning the more hidden set, boom, significant improvement.

If clean, then try a quality scanner to see if any error codes.

 

I've had a similar problem since my initial ownership of my 01 LS430 for about 11 years. Sporadically, upon accelerating from a dead stop or even while driving and accelerating, i feel a "dead spot" where the car does not respond. Upon my second try it will always take off again. No CEL ever. I replaced my MAF with a OEM Denso, plugs, every vacuum line I could find, etc. Since it may go months before it acts up again, I've learned to live with it. Our cars do not have the number of modules that the newer cars have to detect these phantom issues. I've given up trying to resolve a long time ago. No big deal for me.

 

How does you car run when warming up?
Does it run great with plenty of power?
And then after when the engine has warmed up power kinda disappears? Randomly?

If that is you I have a strong hunch that I know what is causing your sporadic sluggishness.

 

Actually, the dead spot can appear at any time. There IS NOT sluggishness. It is more of a "dead spot" when accelerating, but then it's fine during my next depressing of pedal. It's never been a real issue, and sometimes it won't reappear for months, while other times it happens a few times a day for a number of days. I had a tech drive with me years ago, with his lab top hooked into my OBD port and was not able to find anything. I can see it being an issue if it was prevalent or constant, but it's not. It's just one of the
idiosyncrasies of LS430 ownership for me. Aus430.... What is your hunch?... I am very curious to hear as I know others with a similar problem as described in this thread.
PS...A faulty throttle position sensor and/or faulty pedal position sensor were earlier considerations of possible culprits, but considering the cost of just replacing these items with "guessing" didn't seem cost effective.

 

Have you tried a different accelerator pedal sensor? This sensor doesn't have an obd port reading, You can test it with a multimeter but that is very difficult if it is an intermittent fault while driving.
Pedal sensors rarely break on these, although it isn't totally unheard of. A used accelerator pedal from a parts car is pretty cheap and an easy way to rule it out if you feel like it.

My gut feeling is Knock sensors based on the stated symptoms, hard earned experience with these cars and what has been cleaned, or replaced already.
.
There is no OBD output for these sensors (rather annoyingly) so it is tricky to know and/or often overlooked in diagnosing hesitation problems......unless of course they happen fail to the point of throwing a clearly understandable P0330 and/or P0325 code(s). If you suspect knock sensors, the official test involves pulling apart the engine to test them with a spanner and a multimeter...... (In which case you may as well just replace them with new ones anyway to save time/effort).

With that in mind after much tinkering, I think I have stumbled across some telltale signs/ data patterns that can indicate if/when the computer is responding to knock sensor data correctly.

 

I Have the same problem more or less.
When revving the engine in stand it will first hesistate a second (sounds like the engine is blocken or something and then countinue the rev)
When giving it full punch while driving it accelerates extremly slow and has problems finsing the right gears.
also the gearchanges feel a little rough.

i had lexus ls430 pre facelift before and everything was fine there. now ive got the 2004 with 175.000km and this problem....

Ah and also i got to obd codes. 1. P0171 and P0174 Engine to lean

 

check to make sure your catalytic converts are not clogged