I've been tearing my hair out trying to figure this out for about a month now.

Problem 1: Car starts beautifully and idles great for 10 seconds. Then about 25% of the time, it will stumble and run like **** for about 60 seconds, then it will go back to idling smoothly. Occasionally the check engine light will blink and it will throw 16684, 5, and 6, but usually not. When it does, the check engine light goes off when it goes back to normal idle.

What modes does the ECU change between about 10 seconds into running, then later come out of about a minute later?

Problem 2: The car makes normal power up to 1/4 throttle. But, 50% of the time it has no increase in power past 1/4. However, if you floor it and get no power, as you're letting the throttle pedal back out it surges with power at around 1/4. When it's operating normally, it makes full power just fine. It drives along fine on the highway, but when I punch it half the time it will haul and half the time it will do nothing.

Here's what I've replaced so far in trying to track this all down:
- MAP sensor
- Manifold air temp sensor
- Coils and plugs
- Injectors
- Coolant temp sensor

I've spent a lot of time with the ODB running on my laptop graphing values to see if I can find anything that looks bad... but it all looks perfect. The only negative reported via diagnostics is the following mode $06 info that I can't find info on anywhere:

Mode $06, TID $05: Component ID $07 Fail: Value 7922, Minimum 9830

Things I can think of that might cause something like this:
- Intake manifold butterfly valve not operating like it's supposed to
- Loose cabling or a bad sensor for some metric I can't graph with the ODBII

Any ideas? I'm at wit's end.

 

Been reading a lot trying to figure out what could be causing my problems... the two things high on my list are fuel supply and evap / vac system issues.

- When I start the car, I hear what I think is the fuel pump and return from the rear of the vehicle, maybe 20 seconds or so. I don't recal that I used to hear it, but it's possible I just wasn't listening for issues. Do you guys hear a kind of clicking or flowing sound from the rear when you start the car (it's an Avant if that matters here).

- I'm still getting these codes on the highway and no power, though around town it's fine:
17536 Bank 1 Long term fuel trim system too lean
16825 Evaporative emission control system flow faulty

Should I try to replace the canister purge regulator valve and canister purge solenoid valve?

 

is this a 2.8 or 1.8t?? my car used to do that it took me a while to find it was something as simple as the spark plug wires.