Hi,

Have a 2005 Lexus ls430 with about 165,000 miles. Just noticed that when I try to accelerate quickly, the cars rpm rise but the car doesn't want to speed up. Best way to describe it is like I am towing a heavy trailer. I took the mass air flow sensor out and cleaned it with the spray and reinstalled it and still does the same thing. Also seems like the gas mileage has gotten worse.

I have within the past 20k miles replaced:
air filter
spark plugs
y-pipe.

Any help is appreciated. Thanks.

 

Trans slipping? That's the first thing that comes to mind if you don't have codes or any additional info

 

See if behavior changes after disconnecting negative battery terminal for more than 10 minutes.

 

No trans issues that I’m aware of. No check engine light, codes, or slipping. Car seems to do fine when moderately driving and cruising up to speed. When I do accelerate on the highway, it does try to drop down a gear and accelerate but no power. I will disconnect the battery tomorrow and see how that goes. Thanks

 

Does it seem like it tries to rev but hits a "wall"?

 

What you wrote indicates you may have a transmission issue. There are a number of reasons a transmission could be slipping. Worn component(s), solenoid, fluid level, and etc.

 

When you cleaned your MAF did you actually clean the sensing wires or only the exposed temp sensor (the red bulb)? The two sensing wires are deep inside the black tube and are very small.

 

Yes, on the highway when i go to accelerate, the rpms seem to stick around 3500 rpms. The more gas I apply, the rpms don't really go any higher.

 

I only cleaned the exposed temp sensor. Was not aware of any other part that needed to sprayed/cleaned.

 

Shine a flashlight into the end of the black tube. At the very top are 2 small parallel wires. They should be spotless to operate correctly. They somehow get contaminated. Use your MAF cleaner spray with the straw. Don't touch the wires with the straw but flood with enough cleaner until the runoff is clear and the wires look bright and shiny. I'm guessing once you do this your car will run much better.

 

Your cats may be plugged if it is refusing to rev, try a dead start from 0 and see if you can floor it and get past that point of the rev range in 1st

 

I haven't had time to check the MAF but I did unhook the battery for about 15-20 minutes and nothing has changed. I did recently notice a rattle under the car than i have not been able to find. The new y-pipe that I did install is not OEM.

 

Will do next. Thanks

 

Ended up spraying the two small parallel wires and the car does drive a lot smoother and have better throttle response. Something still seems to be holding it back. I am think it may be a clogged cat due to the raddleling under the car. Thanks for the advice

 

Put it in pwr mode and floor it from a dead stop with trac off, see if it can get past the wall and that will tell you if the cats are good or restrictive