Quote:
Originally Posted by docbong88
Thanks, but i'm not sure exactly what that means.
Also, i noticed it seems to be happening when i'm cruising downhill, and when i give it the tiniest bit of throttle, it seems like the engine is revving up to catch up to the speed the car is traveling, IF that makes sense.
Only notice this in heavy traffic stop and go
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Think of your torque converter as a clutch. Until it locks up your engine rpm can vary with load without any change in speed. Once locked up it will tend to change with speed. Sort of the difference between a clutch that slips and one that is fully engaged. If you torque converter stayed locked up it would stall your car when you came to a stop. This actually has been a problem with some older cars when torque converters were first designed to do so, I think some Chryslers had this issue when fuel economy first became a big issue.
Some cars lock up at a magic mph, others do the same but will kick out based on throttle position (I think most will do this now anyway), others will lock up based on current gear. For at least some Infinitis this has been stated as in 4th and 5th gear (note the quote below in regards to 3rd, 4th, and 5th gears). Considering the speed when you are in this speed range it may well be the non-issue many have reported with their cars stumbling at certain speeds, that is the transmission moved or is moving in between lockup and non-lockup torque converter modes. You can see some of this effect when using the manual shift mode.
From the 2007 FSM -
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Lock up occurs at Closed throttle 31-36 mph, released 29-34 mph
Lock up occurs at 1/2 throttle 86-91 mph, released 65-70 mph
Also:
Slip Lock-up Control
• In the slip region, the torque converter clutch solenoid current is controlled with the TCM to put it into the
half-clutched state. This absorbs the engine torque fluctuation and lock-up operates from low speed.
This raises the fuel efficiency for 3rd, 4th and 5th gears at both low speed and when the accelerator has a
low degree of opening.
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