2008GS

Guys, I am not a tech so hence my questiosn; my '97 LS does not idle down from cold start idle for at least 20 minutes of driving. It is above 1000 RPM when cold and doesn't go below that even after highway driving. The car engine is warm, but the idle stays high. I hope this makes sense. I am not getting good gas mileage (surprise). Now here's another strange symptom: when the engine finally decides to return to normal idle (700rpms?) I notice the trans doesnt downshift smoothly into 1st gear when coming to a stop. Is this possibly a vacuum-leak causing both of these issues? If so, how do i find the source? Is this a simple fix? Any ideas? Car has 240K. Thanks!

RA40

iTrader: (6)

Engine coolant temp sensor would be one item we replace in these upper miles. This is a pretty easy DIY.
https://www.clublexus.com/forums/ls-...ange-pics.html

2008GS

Guys, wanted to let you know the issues I mentioned have all been cured...by using PREMIUM fuel. I remembered before the issues began I had filled up with mid-grade fuel and then began noticing idle issues. I recently filled up with premium and the car runs fine now, no idle issues, no clunking on downshift. I did not change the temp sensor. It appears the car is very sensitive to proper octane. Make sense?

Losiracer2

My lockup solenoid in my transmission was bad when I was getting a shuddering when coming to a stop due to my torque converter not unlocking. A better condition OEM used JY solenoid solved it.

Also, try cleaning out your throttle body with Carb cleaner and see if that helps. The problem will come back and isn't related to the fuel octane. I've used 87 before and had no difference in driveability.