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P0101 code after carbon service/injector seal replacement.

wudini

Passed Driver's Ed
Hey all! 2014 MK6 Drivers edition GTI with 77k on the odo. Cobb intake and Cobb AP Stage 1+ About a year and a half ago I had my intake manifold runner position sensor take a dump on me, so I ordered a new manifold and got to work on a carbon service. Got the manifold off, intake ports cleaned, new seals for the injectors, car back together.. Wunderbar. Car runs like it's brand new.

Fast forward to a month ago and all of a sudden I'm leaking fuel. Determine it is the injector seal for Cyl 1 (see photo), off comes the manifold again. Replace the seals on the injector, carbon cleaning touch up, and back together again it goes. Car ran fine at first until a couple of hard pulls in 2nd, and up pops a P0101 cell. I also intermittently get a "too lean off idle, bank 1" CEL (P2177). Car idles rough.. but I can run to the store with it without a lot of drama. Power is down and gas mileage is awful, also there is an RPM surge up to like 1500 RPMs when coming to a stop, and it slowly settles back down to 750. I cleaned the bajeezus out of the MAF with MAF cleaner, and i'll be honest, I did dielectric grease the shit out of most of the electrical connectors when re-installing the manifold to make it easier to remove next time I have to, because I'm sure I will. Not sure this would have anything to do with it, but felt the need to mention. Maybe it could impact voltages? Shot in the dark.

Where should I begin a deep dive? While troubleshooting I noticed the Cobb intake filter was starting to deteriorate.. car has been sitting since I noticed that. Is it possible the filter is just not passing air cleanly? Would running the car without the MAF connected tell me anything? As I was typing this I had the thought to run the car without the filter attached to see how it idles. Intermediate shade tree mechanic, willing to try anything. Thanks in advance for suggestions.


TL/DR:
P0101 CEL after removing intake manifold for fuel leak due to bad injector seal.
 

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BudgetPhoenix

Autocross Champion
Running the car with the MAF disconnected forces the ECU to run in open loop mode which can be useful for telling if you have a bad maf if the car drives better without it plugged, it could be faulty sensor but also p101 and 2177 can pop up with air leaks in the intake track. IMO check your install again and make sure you got the intercooler piping connected correctly along with the TB coupler. Did you use a new gasket when you installed the manifold again? It's recommended to.
 

wudini

Passed Driver's Ed
So after a bit more poking around I'm still at a loss. I can't find any obvious vacuum leaks. I started spraying starter fluid at all the points where I assumed there could be a vac leak to see if the RPMs surged.. nothing. I did notice on my way into work today, I'm getting about 8-10mpg under load and power is way down, boost is almost non-existent.
 

wudini

Passed Driver's Ed
Did you check all your charged air piping?
I did.. it HAS to be something with my charge piping. I'm going to take a shot in the dark later and just take some of it apart. Who knows maybe there's a shop rag in there somewhere.
 

wudini

Passed Driver's Ed
I ordered a new MAF from europaparts.com, which is luckily 2 miles from my house so I had my wife pick it up, will swap it out when I get home. If this ain't it I may be at my limits as far as my ability to troubleshoot go. Also, I'm gonna start spraying starter fluid at potential vacuum leaks to see if the idle spikes.. so irritating lol.
 

wudini

Passed Driver's Ed
So it wasn't the MAF, now I have a P2279 code which basically tells me without a doubt it's my intake manifold gasket. Picking up a new one today, god I hate taking this manifold off.
 

BudgetPhoenix

Autocross Champion
My car doesn't even have the under support bracket on it anymore for the intake manifold. Apparently its pretty common for the dealer to not even reinstall them since its such a PITA but its made the intake manifold job a lot easier the 3x times ive done it lol. The manifold is pretty solidly attached without it still. Anyway hope the gasket fixes it for you but who knows could be anything. How old is your PCV as well?
 
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