So I recently bought this car from a fellow who had only owned it a short time, and really was not a car guy, let alone an Audi guy, but the original owner had done a TON of really nice upgrades to it, like a full Borla Cat-Back exhaust, Eibach suspension, Forge Diverter valve, boost pressure, oil pressure and fuel mix gauge cluster, uprated fuel pressure regulator and pump etc. etc.... and some kind of ECU program. The seller was unaware of who did the "chip". It's veeerrrrry smooth and linear, so I'm guessing it's one of the better companies like APR, GIAC or ECS. The boost pressure gauge shows about 18-20PSI max when flooring it.

So fast forward to today; I take the car to the carwash. I pull out after they've dried it off and cleaned the interior, and I know immediately something is wrong. The car is incredibly sluggish and sounds different. I get it on the highway and punch it... car feels like it's making about 50hp and the boost gauge reaches a maximum 4-6PSI. Normally it runs about 18-20psi. I park the car, open the hood, squeeze the intake hose just before the intake manifold and push the TB open and I could feel just a tiny little bit of resistance pressure once the turbo spooled. Nothing like what it should be. I start getting really upset and decide to get it home so I can start investigating... and BAM all of a sudden, right in the middle of the highway the boost suddenly jumps to 21psi, the turbo sound I'm used to comes back and the car rockets forward. It has behaved normally since then.

Now, I recently gave the turbo a clean bill of health after popping the inlet pipe off an checking for any play in the shaft (none), checked the oil lines to and from and the oil channels, as well as the same for the coolant and everything was close to perfect. The Wastegate spring was strong, wastegate shutter had a tight seal and the valve working properly. I strongly doubt there is anything physically wrong with the turbo.

My first thought was: this car must be chipped by APR with ECMS and one of the guys at the car was accidentally changed programs with the cruise control stalk while cleaning the steering column area.... however, despite the fact that the cruise has never worked, I have never been able to get the car to behave any differently regardless of lots of fiddling with the cruise controls to try and elicit a change in throttle or boost response, or overall performance....

I have no idea what would have caused it, what happened to make it correct itself, or when it's gonna happen again. There is a special version of Murphy's Law applying specifically to cars.... if something bad happens once... someday, it will happen all the time.

Any thoughts?

 

sounds like you were in limp mode for a while. usually it is accompanied by a cel. and by the way, youll never be able to "feel" boost pressure in the hose. the turbo only puts out boost under engine load, so unless you crammed yourself under the hood and let your friend drive, you wont feel the boost. i wouldnt worry about this problem unless you get a cel

 

Check your ECU for fault codes. Even if the check engine light (CEL) isn't on the ECU could still store fault codes. After getting any fault codes, clear all fault codes, and do some research on the codes you might have and/or report back to us.

 

The only code I'm getting is P1476, the same code the car has thrown since I've owned it. The car was vacuum-tested and it held perfect vacuum, but they tested the evap, canister, sensor and so far they believe it's a wiring problem, since there is no actual vacuum leak that they can detect. Getting this code is probably unrelated, since it's been doing that all along and never experienced anything like what I did yesterday....

Any easy way to tell who's software is in the car? I have to think it's something that got tripped by the guys wiping down the controls and the dash at the carwash.....

 

Ill put my money on it simply being a sensor that got wet.

 

So, happened again this morning.... and I can't get it to stop. I get zero boost, after I let off the throttle or disengage the clutch the revvs hang for a minute and go down.... nothing by way of power.

CEL..... code P1476...... again I think this is unrelated as it's been throwing this code since I bought the car and there's no vacuum leak.

This is REALLY frustrating. Usually it's a BOOST leak that sends it into limp..... or at least in my experience that's the most common cause right?

I Got my needlenose pliers and gave a shimmy to the wastegate actuator rod... no problem there nice and tight... quick visual check of all the hosing south of the turbo.... nothing I can see.

Any trick to snapping it back out of limp? I'm starting to think I just got lucky last time with it coming back on......

EDIT: Called my buddy at the dealer who clued me in on a trick to turn the Limp off. He said to turn the car on, let it heat up some.... trace the vacuum hose from the DV valve to the 3-way connection near the front of the Valve Cover and yank it. Manually open the TB a couple of times, turn the car off, disconnect the positive battery terminal, wait 10 seconds, reconnect battery and vacuum.... worked like a charm..... but now how to fix this problem permanently?

Who here thinks the P1476 EVAP / Insufficient vacuum is related? How do we go about fixing a vacuum leak when there isn't actually a leak!!!

 

Anyone?

 

Hmmm. I think the two could be related. If the code is correct, and there is a leak large enough I could see the computer putting you in limp mode. The DV is opened by vacuum so if there is insufficient vacuum to operate the DV it could put you into limp mode for safety. I have had this happen to me due to a blocked DV vacuum port.

I would redouble your efforts on trying to find a vacuum leak. What does your gauge read at idle?

 

At your suggestion I am going to bring the car back in monday and put the fogger on it. I am also going to remove and clean out the DV valve. BTW does anyone remember what the GREEN SPRING is rated for on the Forge DV valves?

 

Up to 15psi I believe.