Baseline:
I have a 2000 A4/Avant 1.8T manual with zero upgrades except for the APR Stage 1 ECU programming. I've had the APR programming for about 4 years now.

Problem:
About 2-weeks ago, I had a CEL and a noticeable loss of power. OBD P0102 error came up so I tried to clean the Mass Airflow with no luck and then replaced it last week. After replacing the Mass Airflow the CEL went out, but I still had a noticeable loss of power and I cannot even feel/hear the turbo engage. In addition, if I accelerate in any gear, I will get an immediate loss of power (almost like de-fueling) when the car crosses over 4000 RPM.

After 3-days the CEL came on again. Today, had the car scanned and I have P0411. Removed the airbox, checked all hoses as well as the hard-plastic hoses going to/from the secondary air pump. Hooked everything back up, reset CEL and the light is off, but still no power. There's no smoke coming from the engine /exhaust and there's no sounds coming from the turbo so I don't think that the turbo is gone, but it's clearly not working.

It's almost like the car is stuck in valet mode - to boot, the CEL programming for the APR chip (engaged via the cruise control SET button) doesn't respond but the cruse control does work when driving. Do I have to do some "magical" ECU reset?

It's like I'm in hell driving a Ford Fiesta or something...
Anyone have any suggestions?

 

Did you ever replace your DV when you chipped your car? It's probably shot by now if you haven't and it might be a good place to start looking for issues.

 

no boost gauge installed?

 

Does it buck,, or lose power smoothly?

 

Update: Disconnected ECU this past Sunday and re-checked vaccum lines. Thinks appear in order on the vac side.

Diverter Valve
Nope, never replaced that, so I was suspecting that it may need to be changed so I'll look into that next.

Boost Guage
No Boost guage installed, so I don't really have a read on what is/isn't being produced by the turbo, but I've driven this car for enough time that I can tell when it's sort of sluggish and a downright dog - it's a dog at this point.

RPM
When the car crosses 4,000 RPM in any gear, it cuts-out "bucks" and doesn't lose power gradually.

Thanks to the three of you for follow-ups. I'll get a DV ordered and go from there.

 

This sounds more like a misfire. When is the last time you changed your plugs?

 

was there a check engine light, or a flashing check engine light when it happens?

 

I haven't had starting, idling or fuel economy issues - I'm still averaging 30-31mpg on my daily commute to work (mostly freeway of course), so I'm not thinking that it's a spark issue and I don't believe the plugs are going to affect the turbo working/not-working.

As for the CEL, it doesn't flash, just comes on steady.
Should have a new DV (710N) this coming weekend - I'll replace that as well as a vac line, test again and post an update.

 

Yes it will. If the car is misfiring, it will be one pulse down and the turbo cannot spool as well, or it will go into a "limp" mode. Additionally, a steady light can also be a sign of a misfire, but there should be a DTC stating thusly. I'm not trying to lead you in a different direction, just clearing up information.

Let us know what you find with the DV.

 

Well, I've finally received some of my mail-order parts, so here's an update;

Replaced the Diverter valve today along with the vacuum hose running from the DV as well as the spark plugs. I still have *exactly* the same problem.... The car starts, idles and runs great - I have a noticable loss of power (can't hear turbo spooling) and the enging cuts out right as the RPM reaches 4000 in any gear.

I don't have anything but guesses at this point.

Here's what I've done so far;
1. Replaced MAF.
2. Replaced Plugs
3. Replaced DV with 710N
4. Replaced vacuum hose from DV (it was looking nasty)

What else could this problem be caused from ?:
* Coil Packs?
* ECU??
* Turbo is blown?

Does anyone have an APR Stage 1 chip in a B5 A4? I have this chip installed and the program settings (set to change chip modes via cruise control button) don't seem to be able to be set.

-Perplexed.