lastguy

still ok but acceleration not as good as say at 100K miles. Spark plugs changed at 60K using 100K denso plugs. a little leak due to gasket and oil pan seal, not big deal as I can add a little at the midlle of oil change. Use synthetic oil since 90K so I changed oil every 8-9K, mainly local road. Trans fluid changed last dec with Mobile 1 75W90, would it be a cause? ATF changed years ago. Coolant also changed a few years ago when it is quite clean a little darker than fresh.
if I remember correctly most of time engine is not more than 2000rpm. now 65mph freeway needs 2500rpm
Now when I press acc padel it doesn't goes faster enough, I wonder how to check and whatever I can recover it

lexo98

iTrader: (2)

Where did you get the spark plugs from?

DMPesso

2500 RPM sounds about right for the GS3 at 65 mph. However if your noticing a decrease in performance or hesitation I would say change the trans fluid again with Toyota T IV ONLY. If your doing a drain and fill you’ll have to do it a lot of times before all the fluid gets exchanged. The car can definitely feel sluggish if the fluid isn’t the same as the Toyota.

I would say 80k miles your spark plugs need to be replaced again. They may “last” 100k but they always get weaker after about 50-60k.

Another thing that made the car much more responsive is o2 sensors and a new MAF sensor. At 140k I’m sure yours is very dirty. You can start by cleaning it you should feel a big difference. I know I did at 145k miles and when I replaced it with a new one the car felt alive again especially at higher RPMs

lastguy

I forgot, may be rockauto? DENSO SK16R-P11 couple of years ago. Looks like genuine.When I changed them at 60K they do worned.
The reason I bought from Rockauto because GS300 original one only last 60K and I checked mfg web to find model lasts 100K miles.
Later on I did purchased Honda plug from ebay and they seems to be faked one - I mean box printing looks a little poor and I got refund.
Can you or anybody confirm that Rockauto sells only genuine Japaness one?

lastguy

All comments vert helpful many thanks!
I do think Trans fluid is the cause and posted a ques on Amazon.
Did you changed all O2? where did you get them or just cleaned (how) them?
I did cleaned MAF may be 1-2 years ago, just a match head like red color glass tip I remembered.

lastguy

I have couple of things to be done a bit hesitate during limited time and skills:
oil pan seal, engine gasket, (some leak, so I add oil in middle of change, consider change oil more frequently)
some ignition cables have fragile plug plastics, suspension boot/gloves broken, and engine mount may also hardened(not sure Taiwan brands ok or not).
My appreciates for above parts brand can be used, 05 GS300 140K.

DMPesso

did this problem start after changing your trans fluid with Mobil 1? I bet it’s because of that. Although it wouldn’t hurt to change plugs again. The part of the MAF that you clean are the silver wires inside which if dirty enough will look black. The red looking bulb on the outside is not the part you clean. Have to spray inside and use a flashlight to see the wires. If there is no check engine light dont worry about o2 sensors until you switch back to Toyota TIV trans fluid

lastguy

My typing has a big mistake!!! I changed ATF years ago by pull out two hoses for flush, no problem! I used toyota one fresh red and old liquid is dark red a little more thick.
Current problem is after I changed the 75W90 that would be the differential fluid, the one at the rear right bottom has two holes one higher than the other, no way to flush.
where to buy genuine Denso SK16R-P11 spark plug, or you can recommend better long life ones?
thanks!

lastguy

where can I buy genuine DENSO or NGK spark plugs online?
from DENSO 2022 catalog, 05- GS300 uses IK20TT, but it is 0.039mm not like original one 0.044 gap.

DMPesso

AutoZone is usually good.

DMPesso

I was going to say the 75w sounds like differential fluid. Maybe it wasn’t filled enough? I saw my mechanic do it he put it in with the hose until it started to spill out to ensure it was full. Get some redline fluid and do it again

lastguy

Yes it is differential that I changed last dec. ATF I changed 3-4 years ago. Sorry for typo.

I checked spark plugs, I still own 6pcs bought from Rockauto not sure whether they are genuine. What I found:
1.NGK Ruthenium life span is 60-120K and IFR6T-11 iridium is 100K, so the former might not be better. Ruthenium has lower melt temp, 2334C vs 2446C
2.Denso TT already mixed Rutheniu, Denso web and manual says IK16TT/IK20TT fit 05 GS300, not sure the difference.

DMPesso

i don’t trust rock auto. They sent me clearly used and abused o2 sensors one time. That made it obvious they either don’t check returns or outgoing orders because it was even taped up wrong and looked nothing like the other 3 I ordered. After that I never order from there again. For oem parts it’s either eBay or discountpartsmonster. Nobody has beat their prices so far online. You also have to be careful on eBay make sure it’s a legit Lexus dealer or parts reseller

lastguy

thanks DM! I see Denso store on Amazon has poor review on its MAF so I'm not sure whether it sells genuine DENSO parts.

any body knows how to test or measure MAF after replacement? below I copied from Amazon on how to know a MAF performs, not sure the way to reset ECU after MAF replacement:
[OEM Toyota MAF sensor. How do I know? I bought the one from RockAuto, another random MAF sensor, and this one. Respectively rating it from worst to best. I have an ODBII bluetooth dongle and the Torque Pro app on my Droid. The STFT (Short Term Fuel Trim) and LTFT (Long Term Fuel Trim) puts out a certain percentage and your ECU has to compensate accordingly. The RockAuto was varying anywhere between 6-30%, the other MAF was pretty good between 3-17%, but this one is anywhere from -0.3-6%.

The stock OEM MAF sensor is within this range and this is the real deal. Get one before it's gone. Remember to reset your ECU and let your car re-learn the fuel curves. I did this on each of my tests and ran it for about a week. The easiest way to reset your ECU is just unplug your negative battery cable for 15 seconds. When you start your car, don't step on the gas just let it run for a minute or two, shut off the car, and take the key out of the ignition. When you start your car again, go nuts if you want. Just keep in mind that the STFT is removed from the ECU memory when you shut off. The LTFT stays in memory and gets calculated, hence Long Term.]

DMPesso

I really don’t think you need to reset the ecu after changing the MAF. It will relearn the change regardless. I noticed a difference in how much better it drove after replacing the MAF without any reset. A ecu reset by itself will make the car more responsive as it’s learning your driving habits so I wanted to feel the effects of a new MAF without anything else. Always good to reset it every once a while anyway