[MidWillamette335d]

I've been meaning to ask this for a while, but is there some function/governor when the car is achieving operating temperature to decrease power? I let the car warm up for about a minute, more when it's cold out. When I'm driving down the highway I can literally feel the car gaining power at almost the same spot every time. Like, I'm cruising and the MPG needle is at 30 or so, then something happens and the car seems to pick up a bit and the needle goes more towards 50. I don't think it's any concern, just curious as to what it is if anybody knows or has experienced the same thing...glow plugs shutting off, some built in tranny function till the ATF gets to temp?

[lnxguy]

How long after you start driving are you on the highway?

[MidWillamette335d]

So, I'll let it warm up for about a minute, drive half mile to the hwy then 35 to 45 to 55 over a mile. I'm about 3 miles in total when it happens. I haven't ran a log yet to see if it's a temp related thing. Another example would be today when I got to work. I had to run to the store about 5 hrs after it was parked. It happened again, but much sooner so that's why I'm guessing it's temp related, just wondering why...or maybe something's not right?

[BB_cuda]

You could run cluster temperature menus. Google unlocking E90 cluster menus. Several youtube videos on this.

Just have menu 7 up (engine coolant temp)

[Tomnavigator]

Midwillamette335D - All modern cars both gas and diesel operate using open loop program in the engine control computer when the car is first started. In the open mode many of the sensors are not used to determine the operating parameters of the car until the car engine has had time to warm up. Some of the sensors such as the oxygen sensor and NOx sensors are designed to operate at temperatures around 1000 degrees and do not give accurate readings at lower temperatures. In the open mode a canned program is used to determine the operating parameters of the engine. In the open mode the car might only use engine RPM, the throttle position sensor, MAF, to determine the fuel injector pulse width. Once the engine reaches certain operating parameters such as the coolant temperature reaching a predetermined temperature, the car goes into the closed loop mode and the car uses all sensors to determine the best operation of the vehicle. Now the car will use the RPM, throttle position sensor, MAP, MAF, oxygen sensor, NOx sensors, inlet air temperature, etc. to determine the best operation of the engine. This is probably why you see a difference in your power and fuel mileage for the first few minutes. It happens on all modern cars. Just most people don't pay enough attention to notice it. Yes, what you are seeing is temperature related. You are seeing the difference between your car operating in open loop mode and closed loop mode.
You are seeing your car go into closed loop mode sooner when you drove it after sitting for a few hours since the coolant temperature had not totally cooled down to the same temperature it was that morning when you started your car.

The engine control computer always starts out in the open loop mode until the predetermined coolant temperature level is reached. A warm car reaches the predetermined coolant temperature sooner than when the car is cold. A hot car that was just turned off will switch to closed loop mode immediately when it sees the coolant temperature is already above the predetermined level. Therefore, you would never know this is happening even though it always happens.

[MidWillamette335d]

Thanks for the response. I guess I never really thought of the open loop /closed loop scenario. My Runner does the same thing, like you were saying, all modern cars. My guess is it began in 96 with OBD2. With my Runner it's completely indiscernible when it happens. With the D it feels like you're turning the a/c off on a 94 Corolla 4cyl going up a hill, like super noticeable. I have the JR 2.5 so maybe I'm just feeling that tune "kick in" when goes to closed and the open still retains the factory settings? I would really love to know the logic behind some of these tunes...

[POBEP]

Originally Posted by MidWillamette335d

... I'll let it warm up for about a minute, drive half mile to the hwy then 35 to 45 to 55 over a mile. I'm about 3 miles in total when it happens. ...

Consider driving off right away instead of idle "warm up" cycle.

The "d" takes very long time to heat up at idle (more than 20 minutes)
While on idle and cold your oil pump is delivering less oil compared to above idle rpm.

Your 3-5 minute trip to highway speeds (55mph) does way more efficient job warming up engine than any idling.

[Spyro235]

I feel like what you're reffering to is the trans converter lockup. The trans monitors fluid temp and won't lock the converter until it's reached a certain temp. Riding the converter heats up the fluid, and all the sudden you feel things lock up. When it locks, it feels like the car picks up a ton of power and efficiency, since the drivetrain is locked together instead of going through the slushy converter.