Poor throttle response + Horrendous MPG

[sheezydontleave]

Hey everyone just hoping someone out there could help me figure out the best plan of action for the issues I’m facing with my car. I’ve searched the web, Facebook groups, YouTube and any other forum I could find but I haven’t had any luck so far.

A little background info on my car, I have a 2012 Audi A4 2.0T Quattro. I am currently running a Unitronic Stage 2 tune, modestly modded, 3” catless test pipe, ECS turbo inlet pipe, muffler deleted, throttle pedal controller, new RevD diverter valve, Turbo outlet noise box deleted, Drop in air filter, and I just put in new spark plugs (BKR7IEX NGK 2667). Oils changed every 3000-4000km. Only pump shell 93 octane or chevron 94 gas.

Now the fun part. Car has good days and bad days, some days super fun to drive feels peppy etc. then I have sluggish days where my throttle response is definitely slower (throttle adaptation helps occasionally). But my biggest issue is my HORRIBLE fuel economy. A full tank gets me 155 miles or 250km. I know these cars are heavy and the tank is not as big as my 2.0T Q5 but this is getting expensive. I literally watch my estimated KMs drop by 10km every 5 minutes of driving.

A few factors that might go into play, car has an exhaust leak from the test pipe install (smells horrible if I use the defroster or have the windows down at a red light). Very shitty crush gasket definitely has a leak where it meets the turbo, also it’s leaking from where the downpipe connects to resonator (these are to be fixed) however fuel mpg was trash prior to going stage 2.

Car had a rough idle on cold start and would almost stall so I just put new spark plugs in hoping this helps, old plugs were literally black.. not sure if this is helping as I just filled up a full tank so fingers crossed I see some improvement. The plugs I installed were NGK 2667 BKR7IEX they are one step colder and my gap measuring tool read them to be 0.028 out the box, I was under the impression they were supposed to be 0.032. Do you think I should regap the iridium plugs to 0.026 or keep them at 0.028?

Now a few OBD2 codes from Carista,

Basic OBD2:
P0130 (Permanent) (Pending) (Confirmed) - O2 Sensor Circuit Bank 1 Sensor 1

P0030 (Pending) (Confirmed) - HO2S Heater Control Circuit Bank 1 Sensor 1

P0130 (Pending) - O2 Sensor Circuit Bank 1 Sensor 1

Got this code once:

P0506 (Pending) (Confirmed) - Idle Air Control System RPM Lower Than Expected

Engine:
04010 (Got this once)

02875

07670 (Get this often)


IMG_4981.jpg

Pic of my car attached :) I’m currently in the process of a B8 to B8.5 front end swap :p

Thanks again ahead of time for any advice.


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[RPMtech147]

I take a strong look at the wiring for the front O2. A faulty O2 puts the car into an open loop, which usually is RICH AF. My old BMW (which always had a check engine light for DPs) would start running like crap and getting horrendous mileage every time it needed a new O2..Seems to eat them every two years. Regardless, Check the wiring to the O2, or just shotgun an O2 at it. Unfortunately, don't have time to get into too much this morning.

[sheezydontleave]

I take a strong look at the wiring for the front O2. A faulty O2 puts the car into an open loop, which usually is RICH AF. My old BMW (which always had a check engine light for DPs) would start running like crap and getting horrendous mileage every time it needed a new O2..Seems to eat them every two years. Regardless, Check the wiring to the O2, or just shotgun an O2 at it. Unfortunately, don't have time to get into too much this morning.

Thanks for the advice, I’m going to check the wiring and hopefully source a Bosch or Ngk sensor asap if it needs to be replaced.

Just to clarify when you say front o2 we’re talking the one closest to the turbo upstream correct?


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[Chillaxin]

Investigate the one that would be before the cat.

[Theiceman]

Thanks for the advice, I’m going to check the wiring and hopefully source a Bosch or Ngk sensor asap if it needs to be replaced.

Just to clarify when you say front o2 we’re talking the one closest to the turbo upstream correct?


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yes

[sheezydontleave]

Thank you everyone for the replies. Just an update, I took a quick look at the upstream o2 sensor harness everything appears to be fine, I didn’t cut through the wire casing but harness was still intact and connected. No visual cuts or damage observed. Although I didn’t disconnect or take it apart. I feel like I do recall during the test pipe install my o2 sensor did have alot of white coloured corrosion on the actual sensor tip. I am hoping to take it off this weekend and inspect it properly. Would the exhaust leak fumes effect the readings? Or would installing a o2 spacer help or would that just make the car run more lean?


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[beatsageo]

First thing I would do is shore up all your exhaust leaks. Leaks can let air in too. Adding a spacer really doesn't change a wide band too much. You can clean all the ash from the gas inlets on the sensor and it will help with response some. Now, only in closed loop is the ECM going to lean out the fuel mix for better economy. This happens under steady state operation within a throttle/rpm/load range window, like 60MPH hwy driving. So if you don't do a lot of that and your economy is crap I might be looking at the fuel injectors, I am not familiar with the UNI tune but i am guessing its also padded rich and not helping.

[mc_hotmail]

First thing I would do is shore up all your exhaust leaks.

Agree. Then you should look for an O2 sensor. These days a good brand O2 sensor like Denso, NTK, Bosch costs just below $100.

[sheezydontleave]

Sounds good thank you everyone. I have my leak narrowed down to 3 bolt connection between the resonator and the end of my test pipe. It’s a cheap Chinese crush gasket so I’m hoping to get a new gasket and add some gasket sealer but I feel like that leak is decently far from the upstream o2 sensor and my fuel economy issues were bad since before I even tuned my car the first time to stage 1+ (currently stage 2).

I did manage to order a BOSCH o2 sensor for $113 USD. Best price I could find so far. My next thoughts are to try and clean the MAF. Does anyone have any thoughts about the PCV failing causing any issues or would that be more of an oil leak?


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[sheezydontleave]

IMG_5494.jpg
Alright just an update for anyone who may have been experiencing the same issues as me! The new o2 sensor seems to have fixed my problems! Took a couple of drives to really kick in but it seems like my fuel economy has already improved and my throttle response is back! Turbo is boosting hard and the rpm’s seem to accelerate faster. My turbo starts to pull around the 2500-3500 rpm range again instead of the 4500 I was seeing before. Thank you everyone for the help!


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