semar: That hesistation is not normal. Are you using a K&N or similar engine air filter, or OEM? Did you solve the problem?

A defective MAF should be the first consideration when experiencing hesitation and performance loss without a MIL. On a used/high-mileage car, this is probably the cheapest "mod" to get the biggest performance gain.

Those symptoms are typical of old MAFs and/or improperly-cleaned MAFs and throttle bodies. Check air filter box to make sure it is clamped down correctly and there are no air gaps, check all intake-related hoses for leaks, check that the throttle body gasket is still good (service manual says it is a one-time use part and to replace every time you disassemble it).

Next likely culprits are the throttle position sensor, then accelerator pedal position sensor, then throttle body motor.

 

The MAF sensor not only gets dirty, but the air flow with small particulates wears on the sensor wire ultimately affecting its performance. The dirtier the air flow, the more wear on the wire sensor from the particulates.

 

I took some snapshots of how the heater and sense components were, prior to cleaning with MAF cleaner, and how they looked after cleaning. I believe the upper component with lots of crud on is the heater resistor and the lower one is the temperature detector. The crud acts like an insulator causing reduced thermal radiation to be detected by the temp sensor. Sometimes people make a mistake and clean the two leads of the the Intake Air Temperature (IAT) sensor which is located on the side of the MAF instead of the heater/sensor pair inside the MAF. I had a brand new MAF available, and I used it, instead of the old MAF I cleaned later on. The new MAF solved my car's hesitation problem.

 

Would you have a how to or pics of it on the car ?

I don't even know where to look or what to change

Would appreciate your help

 

It is where your engine air filter box is. On top, you can't miss it. All you need is a Philips screwdriver to remove two mounting bolts, and pull the cable connector carefully. Then pull the MAF out.

DIY is in the attached link.

https://www.clublexus.com/forums/gs-...and-gs430.html

 

Wow, your MAF is much dirtier than mine was the first time I cleaned it.

 

@Stan
No aftermarket airfilter. PO had all items dealer serviced . According to that schedule there are lots of miles left until next change
Airbox is tight, no gaps on the housing
I will try more when I get a chance to go on a highway. In local traffic there is no chance.
Car has only 116 k miles. Car runs beautifully.Only two small issues:
some windnoise on the driverside (windshield was replaced just prior to purchase; they used the cheapest glass). Wiper linkage has some play (clack clack noise when sweeping). No replacement bushings available, new linkage is over 500 plus labor. Bought another used one that was certified as excellent but showed the same problem.

 

Wind noise has nothing to do with the glass but rather the installation and filing the gaps around the windshield. I also used pretty much the cheapest glass on my replacement and my current windshield is more quiet then the OEM install. How? Because I had the installer fill all the gaps.

 

which gaps are to be filled?
I saw one on top of the windshield. The moulding you have installed can be done only when the glass is out. I tried to fill it with ethafoam but it did nothing to eliminate the "whoosh"
Got a big "star" today on the highway. I even saw the rock coming it was so big