andrew.k

Please shed some insight on my issue if you can.
Car in question picture below.



For the last few months my A4 has been running great, other than a brake light switch that failed, which wasn’t a huge deal.
Now here is where the fun starts.

On Monday I got a check engine light on the way to a business meeting, I thought of it as nothing as we all usually do with these cars, small sensor in which vag-com will enlighten us later. After my meeting I went to a friends shop to diagnose the CEL and it turned out to be a G62 Coolant Sensor (Engine Temperature to Low). In turn I went to the dealership to pick one up. When I got home, I popped off the 3-way hose at the rear of the engine and changed the G62 sensor (lots of coolant spilled out). I then topped up the coolant, reset the codes and called it a day.

Next day I woke up to go to work and the car starts up at 10inhg and bounces around, really rough idle. It has never done this before, then settles to 19 instead of 21inhg where it usually was. Being somewhat familiar with Audi’s this usually indicates a vacuum/boost leak. I though that maybe I cracked the breather hose at the top or something else.
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Pic borrowed from A4Mods (mine was in tact)
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Pressure tested the system until the oil was bubbling, and had to two people listen for leaks….nothing. So I tried propane, engine idle never changed. No leak at all. While I was down there I deleted the N249, and it does hold boost a little better, but that definitely wasn’t the problem.

I changed the plugs; (BK6’s) & visually inspected the coils, purged the fuel rail, all fine. The last thing I checked was the MAF, unplugged it and there was a fluctuation in engine idle, so I’m assuming that it works. I am completely stumped. I now get a traction lamp on top of the CEL saying that it doesn’t receive a signal from the ECU, engine idle is 100RPM higher than it normally is, radiator fans always turn on (I’m thinking as a failsafe), temperature gauge doesn’t go up to 90F like it used to (when hot it sits at 75F on the dial). The G62 code came back. I can’t remember all the code numbers off the top of my head, but I will update this thread when I get home and scan the car again. This is my daily driver; I need to get this fixed. Any advice would be greatly appreciated.

Tid Bits:
Car boosts to full PSI WOT
When warm idles 100RPM higher than usual but at the correct vacuum 19-21inhg
Old plugs had been fouled (gapped to .28 – BK6’s) – 5000kms on them
Radiator fans turn on right away – turn off when the cars warm (They never used to turn on on start-up for no reason)
Mod’s are listed in my signature if that helps, but I have been running them for over a year successfully until now.
Reasons for still getting the G62 code: No clue, is there another one?
Reason for the traction lamp: No clue
Reason for getting a knock sensor: Probably because it’s acting erratically
Reason for temp being off: Spontaneous mood of the thermostat due to all this ?