I have 2004 GS 300 with 233k on the odometer

I have been having power and acceleration issues for some time (over a year). Car struggles from zero then levels off at about 40 MPH. I would like to do all I can before going to a mechanic for "diagnosis" and end up wasting money. I initially thought it was a transmission problem, but a tranny specialist said nope it's something else, more likely the exhaust system.

Here're some more details:
- There are no error codes
- Both catalytic converters were replaced 8 months ago - for SMOG (so I'm doubting it's the cats)
- I cleaned the Mass Air Flow Sensor
- My air filter is clean
- I replaced the Air Intake Resonator Tube/box several months ago

Has anyone experienced this problem with the same car or have any idea what the problem is? Thanks!

 

What part of Cali are you from? If you're North of San Francisco I might be able to check it out.

Have you pulled the codes? That should be first. AutoZone or O'Reilly can do it for free. This will get you going in the right direction.

Does it only accelerate even you get towards the bottom of the throttle? There are some sensors and motors in the throttle body that can cause the issues you are having


Check your transmission fluid while it's running in park as well, make sure it's between cold and hot

 

Thanks for your response. I'm in the East Bay.

As I mentioned, I have no error codes. The car barely moves. I have floored it while at small inclines (freeway entrance) and it does nothing but scream.
It takes a while to get to 45 MPH - once there it levels off and rides normal. I noticed the RPM meter goes much higher than normal upon acceleration and then goes down after about 45 - 50 MPH. I will check the transmission fluid. I have seen videos indicating it's a clogged exhaust. Do you believe it's something else?

 

That is a slipping transmission. High RPM means the engine is overcoming the clutches ability to hold. Make sure the level is full (or at least readable on the stick) before anything. It would have to be really low to slip, and usually you'd have shifting issues, not slipping. Don't waste money on a fluid exchange either. The clutches are smoked so the trans needs rebuilt or replaced. Especially if this has persisted for a year. You'll actually make it worse by taking out the fluid that has all the clutch material in it. It's helping the clutches grab at this point.

 

TrueGS300, thanks for your input. Please read the original thread.

I already went to a transmission specialist who inspected the car said said there’s nothing wrong with the transmission. Hence I’m leaning towards a possible exhaust system issue. But thanks again for your input.

 

The engine wouldn't "scream" if the exhaust is a problem. Find another transmission shop for a second opinion. The little bit you've mentioned points away from an engine problem and towards the rest of the drive-train (torque converter / internal transmission).

 

It sure sounds like a transmission problem. Fluid level, clutches or torque converter.

take it to another shop

Maybe post a vid of the gauges as the case tries to accelerate from a stop

 

How does it respond when you manually shift thru the gears? If you pull it down to low, does it seem to take off any better? Does it change to the next gear fairly quickly? Or does it take a little bit of time to respond? Try driving it around for a little bit and do the shifting yourself and see how it acts, if it shifts better at higher or lower rpm? Or how it acts when u down shift to slow the car down? Or if it doesn’t respond well in any situation

 

Any update on this?