AUGuy21

I have an '02 GS430 with 55K and I got the car w/ 41K back in Feb. '07. Almost always put Exxon 93 in it. Every now and then for the past 9 months or so, I'll press the pedal moderately from a stop or around a corner at a moderate speed. When the car is operating normally, I expect the car to upshift and then reach maybe 3000 RPM's before it downshifts. However, as I press down the pedal awaiting for acceleration, I feel the car bog down, not upshift and not accelerate properly as it should. So, I'll press the pedal almost to the floor to get it up upshift and the engine will hesitantly rev to about 4000 RPM's, but the car gains speed at an extremely slow rate in relation to the tachometer swell. During the acceleration you can hear the engine wheezing for air and you feel the car "jumping" back and forth as the RPM's climb but the car barely gains speed. Seriously, a YUGO would out sprint me when this is going on. I put in a K&N drop-in about a month ago but I still had these problems with the OEM air filter. When first installing the K&N, I could tell the car breathed better. So this couldn't be causing the problem. I also installed OEM 18's two weeks ago and I've been pretty easy on the gas b/c the car feels heavier with the bigger wheels. Lastly, the check engine light has NEVER come on.

Has anyone ever experienced this acceleration problem? I remember reading about replacing a "throttle position sensor" and/or "accelerator pedal assebembly" for the drive-by wire system which could be causing this. I also think it could be something related to the fuel system. Maybe it's not getting enough fuel when I press down the pedal? Any help would be appreciated. Knowing my luck, I feel the car will start working normally if I wake up at the crack of dawn to take it to the dealership. I never have time to drive it by right when it starts acting up.

GSteg

iTrader: (15)

Check the basics like the spark plugs.

UncleRay

iTrader: (2)

I had a similar problem when I first bought the car. I had a mechanic inspect the vehicle and he said that the spark plugs needed to be replaced, and the transmission oil was filthy. Not your ordinary transmission oil with 20% of the tank filled with little chunks of metal, but 90% of the oil was full of metal clippings from the pistons. I had two pistons replaced due to horrible misfires, had the spark plugs changed, and I had the transmission oil flushed, filled, flushed, filled, drained and then filled one last time.

You might also want to check your battery. It may not be giving off all of its' juice.

Take it to a dealership for an inspection only. If and when they do find something wrong, let them fix it. It's better to have a Lexus dealership fix it rather than some grease monkey :P

AUGuy21

Thanks for the info. I had the transmission flushed at the dealership about 6 months ago and installed a new battery last Thursday. I had to unplug both positive and negative lines for about 4 minutes when installing the battery, so I don't think the ECU had time to reset itself in that short a time.

If the spark plugs needed to be replaced, wouldn't I be hearing some misfiring and sputtering at idle? The thing idles as smooth as silk.

GSteg

iTrader: (15)

My neighbor had this problem with his old truck. I dont know about his idle, but he said acceleration was crap and kind of hesitating. Then again, he has an Isuzu Hombre (rebadged chevy S10) and it's not known for the smoothest engine

Turned out his plugs needed to be changed and now the car drives fine. It doesn't take too long to check them out.

tommy152

Maybe the MAF sensor needs cleaning?

UncleRay

iTrader: (2)

You would definitely be hearing some misfires, but then again a lot of times you don't =/. I used to own a 1994 Saturn v4, and it was garbage. It used to break apart really easy. At idle, the car would shake, and I finally realized it was the spark plugs. Had them changed, and the car wasn't sluggish on acceleration anymore.

Get them checked out, you never know!

SeattleGS400

iTrader: (1)

Try cleaning your MAF sensor and throttle body--it cleared up my hesitation issue and gave my car a smoother idle. Here's the DIY I recently posted:

https://www.clublexus.com/forums/sho...d.php?t=345147

Takes about 30-45 minutes.