High RPM power loss... RESOLVED!
10-06-2008, 03:47 PM
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High RPM power loss... RESOLVED!
I'll start by reposting the whole story of what's been going on.
Background: 2008 Audi RS4. K&N air filter, Revo performance flash, Milltek full non-res exhaust.
Symptom: Under full throttle, would lose power at about 6,500 RPM. The car would flat-line from 6,500 RPM and up, so noticeable that your head would fall foward because of the loss of momentum. Would also feel a rapid stutter at about 7,000 RPM, and sometimes even at about 3,000 RPM.
I never had an EPL or CEL. Vag-Commed the car and there are no DTC's or codes of any kind.
My attempts to resolve the issue in the following order. Based on other's solution to a similar problem as me:
1: Oil from the K&N filter could've damaged the MAS. Swapped it out for a new one. NO SOLUTION.
2: Valve from the air box flap can stop working due to a faulty vacuum tube. I removed the flap. NO SOLUTION.
3: Installed 8 new coil-packs and spark plugs. NO SOLUTION.
4: Bad fuel pressure sensor. Applicable to only a certain range of RS4's (not mine). I replaced it anyways. NO SOLUTION.
5: Flashed the ECU completely back to stock. NO SOLUTION.
Finally: I decided to take the car to the dealer. They determined there is a loss in Vacuum from the car's vacuum system. First place they look is at the ends of the aftermarket exhaust....
SOLUTION! Since I have an aftermarket exhaust, the exhaust valves that are activated by the sport mode feature are eliminated, leaving the VACUUM tubes that control those valves out in the open. Those tubes were capped off after the installation of the Milltek exhaust. There lies the problem.
They discovered the caps had dislodged, creating a major loss in vacuum in the entire system, which results in an uncontrolled valve/vacuum condition in the motors air management system (intake manifold flaps, air box flaps, etc etc).
They plugged everything up with something more permanent, and WOW! The car is 100% back to normal with full power in the entire range and that lovely power boost at high RPMs.
I'm so relieved it was something as simple as this. This is another one to add to the books guys! Hope this solves the problem for someone in the future.
-Dave-
Background: 2008 Audi RS4. K&N air filter, Revo performance flash, Milltek full non-res exhaust.
Symptom: Under full throttle, would lose power at about 6,500 RPM. The car would flat-line from 6,500 RPM and up, so noticeable that your head would fall foward because of the loss of momentum. Would also feel a rapid stutter at about 7,000 RPM, and sometimes even at about 3,000 RPM.
I never had an EPL or CEL. Vag-Commed the car and there are no DTC's or codes of any kind.
My attempts to resolve the issue in the following order. Based on other's solution to a similar problem as me:
1: Oil from the K&N filter could've damaged the MAS. Swapped it out for a new one. NO SOLUTION.
2: Valve from the air box flap can stop working due to a faulty vacuum tube. I removed the flap. NO SOLUTION.
3: Installed 8 new coil-packs and spark plugs. NO SOLUTION.
4: Bad fuel pressure sensor. Applicable to only a certain range of RS4's (not mine). I replaced it anyways. NO SOLUTION.
5: Flashed the ECU completely back to stock. NO SOLUTION.
Finally: I decided to take the car to the dealer. They determined there is a loss in Vacuum from the car's vacuum system. First place they look is at the ends of the aftermarket exhaust....
SOLUTION! Since I have an aftermarket exhaust, the exhaust valves that are activated by the sport mode feature are eliminated, leaving the VACUUM tubes that control those valves out in the open. Those tubes were capped off after the installation of the Milltek exhaust. There lies the problem.
They discovered the caps had dislodged, creating a major loss in vacuum in the entire system, which results in an uncontrolled valve/vacuum condition in the motors air management system (intake manifold flaps, air box flaps, etc etc).
They plugged everything up with something more permanent, and WOW! The car is 100% back to normal with full power in the entire range and that lovely power boost at high RPMs.
I'm so relieved it was something as simple as this. This is another one to add to the books guys! Hope this solves the problem for someone in the future.
-Dave-
10-07-2008, 01:39 AM
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Odd.. So u think the tech lied to me? He showed me the prob and how he fixed it..
what vacuum lines are you talking about that you left open? If you're talking about your exhaust lines, do you know for a fact they were left unplugged (open). When I mentioned unplugged, I'm talking about disconnecting the exhaust tubes from the valves and not plugging them shut.
What happened after 6 months that made you decide to close the lines?
What happened after 6 months that made you decide to close the lines?
