Fault Code: P2004 & poor gas mileage

[DownhillA4]

Hey everyone,

Been awhile since posting on here. Quick update, B7 Avant 2.0T, auto, all new valve cover gasket, PCV, k03 turbo and all component within the last 5k miles... still being daily driven that just hit 280,000 miles and still love every mile.
Recently I have notice my gas mileage has gone to crap and slight misfire on startup (put put noise) but no misfire while driving. Just takes forever to try and get up to speed or merge onto a highway so I know something is wrong.

I recently pulled codes from the car since the check engine light has been on & received the below:
P2004 - Intake Manifold Runner Stuck open Control Bank 1
P0171 - System Too Lean Bank 1
P0141 - 02 Sensor Heater Circuit Malfunction Bank 1 sensor 2
P0304 - Cylinder 4

The only codes I have never seen before after 10 years of ownership is the P2004. I did some research on this code and it appears this part can be replaced - Intake Flap Motor: 06F133482E - but I have also found OLD threads saying you can reflash the car to remove this code WITHOUT changing the part? Is this actually true if using VAG-COM... if so, how is it done? I'd prefer not to curse for 2 hours changing another expensive PITA part if I don't need too. ;)
What adaptation values would need to be cleared?

Another thing I suspecting is... are these codes related to needing a carbon clean? Car was last carbon cleaned at 150k miles so I wouldn't be surprised.

Thanks for any insight in helping me get my fuel mileage back!

Oh and because everyone likes pictures of the car that has the issues, here is the most recent photo of the DD at 278k miles a few months ago....


Cheers

[CycloSteve]

Based on the above I would definitely do a full carbon clean, and have your injectors cleaned/balanced at the same time.

Secondary issue may be the downstream O2 sensor is on its way out.

[DownhillA4]

Thank you for the response, yeah I have a feeling its way overdue for carbon clean.

[Theiceman]

personally i don't think carbon cleans do anything, sounds like your car is broken and needs fixing.

before doing anything else you have to fix what you can see..

Replace your 02 sensor, i think the two white wires on this car are the heater, if they are open circuit , the heater is toast so get a new 02 sensors

The intake change over between short and long runners affect the torque at the low end. Sounds like you dont have any, so id be fixing that runner flap actuator.

As always, fix what you can see, before you try fixing what you cant see.

[Theiceman]

I have heard there is a kit available to fix the broken linkage on the intake runners...
I would take the intake off and see if you can fix it if you can determine it is a mechanical breakage . you might find other things while you are in there.
once you have fixed all your codes, now we will have a baseline to work with

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[DownhillA4]

Alright team so I replaced the intake flap motor as well as a complete new linkage because when I went to pull the intake flap motor off... the linkage was just dangling down because the plastic was cracked.

Also did new NGK spark plugs since the car had 60k miles on the previous set (a lot of white buildup on the plugs).

Intake Flap Motor fault code is now gone, still have a cylinder 4 misfire only.

AS OF TODAY: Cleared the codes after the intake flap motor change, no check engine light on initial startup.
Drove car and it pulled amazing like it should & no check engine light.
Turned car off and back on after an errand, solid check engine light back on for Cyl 4 misfire and car not accelerating as fast again.
Cleared code again, drove it and Cyl 4 misfire code back again only.

brand new intake flap motor, verified the linkage is still on, new NGK plugs, NEW coil packs yet still a cylinder 4 misfire even though car is idling smooth and still loss of acceleration.

Next I'm going to see if maybe the wires going to Cyl 4 have damage somewhere. Possible a head gasket leak or something causing cylinder 4 misfire?

[CycloSteve]

Ranked from easiest to most time-consuming/costly:

Wiring - worth checking both the coilpacks and injector looms and connectors. Both B7s in our stable have been fine, but my son's prior B6 had crispy-fried wires going to the coilpacks causing misfires. Connectors also tend to crack or get broken during service.

Compression - test will definitely help rule that out. My recent check was 170-175 across the board cold, and without monkeying with holding/forcing the TB open.

Injectors - could very well need to be serviced/balanced. Had mine done recently, and was a little over $100 for all four. Money well spent...though you will need to remove the intake manifold.

Carbon Clean - as noted previously do the carbon clean while you are in there with the manifold removed. I was amazed how well my motor ran with the amount of carbon build up on the valves, intake runners and manifold.

[80sGuy]

personally i don't think carbon cleans do anything, sounds like your car is broken and needs fixing.

before doing anything ..

Replace your 02 sensor, i think the two white wires on this car are the heater, if they are open circuit , the heater is toast so get a new 02 sensors....

As always, fix what you can see, before you try fixing what you cant see.

Yep!

[Theiceman]

sounds like you are making progress..

now that you have a spare coil , does it run rough at idle ?? do you have vcds ?? if you know it is misfiring at idle, you should be able to connect your spare coil to the harness with a spare plug and ground the plug with a cable to a ground.. you should be able to see if it is firing.. bar careful you don't shock yourself. you might see if you are dropping spark or something ,,

[DownhillA4]

Okay so update on all this...

Finally got around to buying a carbon clean kit from Amazon and new injectors + intake manifold gasket.

Did a carbon clean and new injectors + seals. I am shocked how good the valves looked for being over 120k miles since the last carbon clean, it looked great, definitely not a lot of carbon but cleaned anyways since I was in there.

Car runs strong now when accelerating, fuel MPG is back up from 16 to over 25.

I retorted the intake manifold bolts after the re-installation because I was getting multiple misfires while idling.

Now I have a slightly high idle when the car is warmed up (about 950-1k at idle) and now have a check engine light for P0171 (system to lean)

So I improved the car performance and MPG but now plagued with another check engine light. I am thinking a vacuum leak somewhere. Looks like I'll need to buy a smoke kit.

[Jayz691]

Def sounds like a vac leak. You can unplug the MAF, to put it in open loop and see how it runs. Normally if you have a small vac leak it'll run good with MAF unplugged.
Or clear codes and monitor group 32(LTFT). If you have a vac leak your idle trims will rise steadily, compensating for unmetered air.
See what your trims are before resetting.
Were the injectors OE Bosch/genuine?

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