Erratic Rev's

[Troysc04]

Hi, 

I have had my Lexus IS250 SE-L for 2 months now and have noticed that on my commute to work, whilst travelling uphill at a steady 30mph in 5th that the revs sit around 1100 to 1200 then all of a sudden the engine noise changes, as if its dropped down to 4th but it is still in 5th, and the revs shoot up to 1800 without any significant increase in speed. Then after a couple of hundred yards, the engine noise drops again and the revs drop back down to 1100, this then repeats all the way up the hill.

Anyone any ideas why? 

if it dropped down to 4th because we are going up hill slow and steady I could understand it but it stays in 5th!

Cheers

[C Andrew Green]

Hi,

My understanding is that the Lexus 6 speed gearboxes have the ability to lock up the torque converter so that it drives at 1:1, thus removing the permanent slippage that is present in a fluid flywheel / torque converter and improving fuel efficiency.

I can certainly detect it locking and unlocking,, it's almost like a 7th gear, I commute on the A34 in Oxfordshire / Berkshire most days and normally where possible wind it up to 70 Mph GPS and engage cruise control, the revs will be ~2200 and 6th gear, when you come to some of the hills the revs will pop up to ~2700 without changing gear and when it flattens out you can just feel it lock back up and the revs drop back 500 rpm or so.....

You could engage 'S' mode and shift down so that it stays in 4th I suppose, 1800 rpm isn't exactly racing the engine, I only tend to use downshift in 'S' mode as a low hold to avoid riding the brakes on downhills. Also are you in standard mode or 'ECT/PWR' mode? I found the extremely non linear throttle response in standard a bit odd so mine is permanently in 'ECT/PWR' mode which also downshifts much quicker if you brake firmly.

Andrew

[Troysc04]

Thanks Andrew. I'll give that a go and see what happens.