Some days I get in this car and it will throw my head back on take off with TC on and smoke away from a stop with the TC turned off. Next time I get in, it will act like I started out in second gear. DIC shows only two codes and both are HVAC codes. I thought it was heat related, but no. I thought it was gas related, but no. I thought it was a TC issue (not disengaging) but it does not appear to be that either. I can't find any condition that fits a pattern. It does not depend on trans temp as far as I can tell. The ONLY other condition that exists is that at high RPMs it has a whistle that sounds like a turbo when I stomp it. At the shift it goes away until RPMs climb again. I have no idea what that is.

It has NO mods, bone stock 28k miles. automatic trans.

Any ideas?

 

I'm guessing it's due to the transmission calibration and torque limit. Get a tune done to do away with torque limits and fine tune those shifts and TC.

 

Can you explain how this is a suspected cause? What condition makes it just fine one minute and then not fine the next?

 

Sorry it took me awhile to see your response. I haven't been on here a lot lately.

Transmission calibrations aren't really my thing, but I am taking a shot at this and I may be completely wrong. These are just some of my thoughts, it's hard to really know with out seeing the car.

Factory transmission calibrations are set-up for comfort and durability over performance. That being said the car is set up to provide the driver requested power, but smoothly. There are several calibration points that are set to provide protection against damaging components as well. It's torque limited depending on what gear you are in and several other conditions like having traction control on or off. Another key point in transmission calibrations is its ability to adapt and anticipate driver input. If you just went on a WOT blast, it may hang the throttle open a bit and keep the shift points high and firm.

So my theory is it's possible that the conditions were not of the calibrations liking, so it restricted torque output. OR it did not anticipate a WOT condition so before it knew what you wanted it to do, it didn't take off like a bat out of hell.

Another possibility is within the engine's tune. Power enrichment mode, or WOT, is programed on a delay. Meaning you put your foot down, the PCM sees this, waits a moment, and then delivers. Once you are in PE mode it will stay for a bit until things settle down. Again, a tune could eliminate this delay.

Just some food for thought.

 

A new development / update. Tonight I tried to do a brake stand burnout. Turned off traction control and saw the light come on on the instrument panel as well as the message that it was off. Tried a barkestand and felt the engine sputter and the car just did not respond. It barely pulled against the brakes. I held the button down to go in to competitive driving mode and held the brake. This time it broke the tires loose. Why? Off should be OFF, why would it behave as if it were still on? Could this somehow be related to what I "think" is bad bearings? Could the speed sensors be bad? Would that effect TC even when it is OFF?

 

Well off is not completely off unless you press the button and hold. It gives you a little bit more play but the car is still in control. This works the same way in BMWs.

 

Its the other way around. the first brief press is in fact off (really off, AH/TC) the second long press is Competitive Mode (TC off AH still on).

 

Correct. That's why I'm puzzled.

 

Wow this is the first time hearing all this from someone else and am noticing the same stuff. I also have an '04 A4. I also notice that whistling sound, I think it's just the aero of the car cutting through the wind, sounds really cool. From what it sounds like sometimes you aren't getting full acceleration when you go WOT? I had/have that problem too but ever since I got my first oil change, every time I put my foot down it goes hard.

 

Not an expert but . . .

You know we also have tourque management in the auto (in addition to AH and TC). If the car thinks you're gonna break something, it will retard the spark and you will get that "bogging" thing you are describing.

Not saying there's nothing wrong in anyone's specific case, but turning off AH and TC does not mean you are in complete control, its still a drive by wire system.

You may smash the pedal down and the throttle may only open 20% in some conditions (no direct mechanical linkage, you get the throttle open as much as the programming thinks is safe and some conservative restraint went into the programming for general purpose drivers).

 

Doesn't torque management only really come into play when shifting? I understand it will cut the power if it is in a limp mode or if AH and TC kicks in, but I wouldn't think they would have any torque management otherwise except when kicking in on a shift. I know how that things worked in my last car a Dodge SRT8 with Mercedes transmission and electronics.

 

Well after driving it last night it definitely seems like Competitive Mode does exactly what it is supposed to but TC "OFF" appears to still be "ON" for some reason. There is no difference between on and off. The only time the car wakes up is in Comp mode. Othewise, I feel like I am towing a house behind me.