redfish0

i have noticed one additional feature of this problem. I want to share it with you all who are knowedgable and see if it sheds further light for diagnostic purposes. I noticed that the first 10 minutes after strting the cold engine the engine does not cough or hesitate during the 40-50 mph range. After 10 minutes or so the problem surfaces and stays that way the rest of the day. Perhaps it is the plugs and I will start there. Any other thoughts with this new info?

Thanks Turbo. I will give it a shot and see if it helps. Is there a computer I could it up to in order to find out exaxctly what is wrong?

since I am a neophyte, pleae tell me what the TPS is and I will check it.

I used plugs from autozone. they were platinum dual post bosch 2. Should I have used others?

I have a 99 gs300 with 112k on it. Best car I have ever owned and I have had no propblems until now. I recently had maintenence performend on my car to include timing belt, serpentine belt, oil/filter, air filter, plugs, transmission fluid, etc. It ran great before but now there is an issue when I drive through the 40-50mph range. At about 40 mph if I try to accelerate gently the car coughs and hestitates and almost shakes. Once I get to 50 mph all is well. If I accelerate vigorously between 40-50 mph I have no problems, just gentle acceleration, like after I coast through a toll plaza causes a problem. Curiously my mpg has gone down as well since the service was performed. App. 415 miles per tank and now about 350. Any thoughts? I disconnected the battery overnight to reset the computer which was ineffective. Any thoughts? I thank you all in advance.

Great! Do you know of somplace i can get one to fix it? I can't seem to find it anywhere on the web. Is there an on line tutorial on how to change it?

I have a 99 gs300 with 108k on it. I have never had a problem with it whatsoever until this minor issue recently. About every 3rd time I try to start the car, I turn the ignition and nothing happens. The dash panel lights are illuminated but the starter does not engage. At that point I return the key back to the original position and turn again. Sometimes it starts on the second attempt but often it takes up to four tries. The battery is fine and I assume it is some kind of electrical issue. Any thoughts? I thank you all in advance for your help.