No more hair to pull out, Throttle response!!
#63
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My girlfriend's A4 on the other hand was doing PRECISELY what your car is doing. Drove fine. Had power. Idled fine. Redlined off the line. But if you shifted its gears a few times up and down, up and down, and then tried to peg it...it acted exactly as your car does, absolutely identical. I witnessed it myself numerous times.
The cam shaft turned out to be culprit, and as a result was screwing with the car's timing. The cam follower ended up damaging the cam shaft a bit, and that caused problems with the tension of the timing chain. So it was a domino effect of those three things.
The cam work performed to the car completely fixed the acceleration issues. But eventually the tension started causing noise months later, and fixing that got rid of the noise, which your car is not exhibiting. I do believe accessing the cams is a relatively easy process on our cars. And I firmly believe you should start there.
I will show this video to Performance Motorsport when I go there next weekend to get the alignment done with my new springs.
#64
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So, how do you explain the fact that the engine runs well immediately after the car is brought to a stop, but only until the first time the throttle is released. Also, why would the engine run well when the cruise control buttons are used to accelerate the car.
If it's something with the engine, I don't think it would magically cure itself like that, and then go bad when you use the throttle pedal after it's been released one time.
If it's something with the engine, I don't think it would magically cure itself like that, and then go bad when you use the throttle pedal after it's been released one time.
On the other hand, flooring it or desiring speedy acceleration is triggering a timing malfunction because now you're making use of the car's variable timing, which again, directly relates to the operation of the cam. Basically, the volume of air taken in is tremendous no matter the operating speed of the vehicle and is instantly accessible for combustion. The variable aspect comes into play on how the car creates the combustion process, and at what rate. That rate is variable and dependent on throttle for much more instantaneous response and more mid-range power. Where as in the past the valves operated one after the other, (valve opens > air goes in > combusts > exhaust valve opens > exhausts) with modern day motors that have variable cam/valve timing, the valves can actually operate in multiple stages: simultaneously, sequentially, or staggered with a variable rate of operation. With variable timing, there is always air in the intake manifold just waiting for valve actuation to let it in for combustion. Without variable timing, the amount of air in the manifold is significantly less, which requires additional throttle input (wasting gas) and laggy response overall because the valves are operating inefficiently.
So basically, if the intake valves aren't operating like they should under full throttle, the car won't go anywhere. And there are a variety of factors that can cause such an issue. One being something simple like the follower. The worst being the intake cam shaft assembly.
Like I said, my girlfriend's car had the very same issue. It was perfectly drivable, but randomly wouldn't go anywhere when floored.
Last edited by SniperHunter; 07-03-2011 at 02:15 PM.
#65
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From OP's post #1 on page 1:
"The funny thing is, Car runs great using the cruise control switches on the steering wheel, I can rev to redline using the ACCEL/RES switch if i want."
That doesn't sound like he's puttering around.
"The funny thing is, Car runs great using the cruise control switches on the steering wheel, I can rev to redline using the ACCEL/RES switch if i want."
That doesn't sound like he's puttering around.
#66
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Err...he can slowly reach redline using cruise control. Big deal? That is precisely what puttering is, hell I even added to that by saying accelerating like a turtle has little effect to trigger this. Do you know how long and slow of a process it is to use cruise control to redline? Accelerating that slow isn't going to trigger the problem. You don't seem to understand what I'm saying.
That Accel/Res switch isn't replicating wide open throttle. It is merely a way to slowly increase speed. Once again, something I defined as accelerating like a turtle.
That Accel/Res switch isn't replicating wide open throttle. It is merely a way to slowly increase speed. Once again, something I defined as accelerating like a turtle.
#67
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So, we have a question for the OP. How fast does the engine accelerate when you use the CC buttons? WOT? Slowly? Something in between?
I rarely use CC, and I've never used the CC buttons to make anything other than minor speed adjustments with quick taps on the buttons. I have no idea what happens when you just hold the ACCEL/RES button down.
I rarely use CC, and I've never used the CC buttons to make anything other than minor speed adjustments with quick taps on the buttons. I have no idea what happens when you just hold the ACCEL/RES button down.
#69
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Wouldn't the transmission shift into a higher gear long before the engine gets to redline if the engine was at a low throttle opening?
I'm anxious to hear from the OP about this?
I'm anxious to hear from the OP about this?
#70
Automatic Speed Control Device (ASCD) allows a driver to keep vehicle at predetermined constant speed
without depressing accelerator pedal. Driver can set vehicle speed in advance between approximately 40 km/
h (25 MPH) and 144 km/h (89 MPH).
ECM controls throttle angle of electric
without depressing accelerator pedal. Driver can set vehicle speed in advance between approximately 40 km/
h (25 MPH) and 144 km/h (89 MPH).
ECM controls throttle angle of electric
#71
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Once again...cam assembly, inspect it. I wrote all that and you're fixated on the cruise control. Using cruise control will almost never trigger a timing issue. I'm trying to help you understand that.
#76
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Just read through this whole thing. I am really interested to see what is causing this. Sub'd!
I was going to put in my 2 cents, but you guys covered a lot of possibilities.
I am leaning towards what Arnold is saying. I understand the difference between running it to redline with the CC controls and the the throttle. Big difference in throttle position and air coming into the engine.
One thing though; how can you get it to redline with CC? I know in my DD car (it's a manual transmission), I can put it in neutral on the interstate and set CC and it will go to redline very slowly and then just bounce off rev limiter. How is this done on a car with a auto tranny?
I was going to put in my 2 cents, but you guys covered a lot of possibilities.
I am leaning towards what Arnold is saying. I understand the difference between running it to redline with the CC controls and the the throttle. Big difference in throttle position and air coming into the engine.
One thing though; how can you get it to redline with CC? I know in my DD car (it's a manual transmission), I can put it in neutral on the interstate and set CC and it will go to redline very slowly and then just bounce off rev limiter. How is this done on a car with a auto tranny?
#77
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The clutch switch is supposed to cancel the CC when you depress the clutch, so how do you get it into neutral?
I don't understand how the OP is getting the engine to go to redline, either. I've driven cars that would downshift in CC going up a steep hill, but they would upshift long before the engine got to redline when the road flattened out a little.
I don't understand how the OP is getting the engine to go to redline, either. I've driven cars that would downshift in CC going up a steep hill, but they would upshift long before the engine got to redline when the road flattened out a little.
#78
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But I can't see this problem occuring with a camshaft or timing issue, unless the OP is describing it incorrectly. What my money is on, is some type sensor issue. But the symptoms seem a little odd.