DaveOx

So I have been occasionally seeing an intermittent short to ground on EGT sensor 2 with the VAG-COM and an implausible signal on Bank 1, but the other day it threw a steady CEL. Now I have misfires on 4,5,6 but the codes will clear and not come right back.

I read a service document in the manual that says bad plugs/coil packs can CAUSE the EGT to read an implausible signal. But then I've heard some say that the EGT can CAUSE the misfires. Which is it?

Today I will be checking all the connections to the EGTs and also changing the plugs.

BTW, is the "EGT sensor 2" really in Bank 1 (passenger side)?

paulroad

its not the plugs.. change you coil packs on the 4,5,& 6 with the 1,2 & 3.

Clear your codes and see what comes back.

If you get misfilres on 1,2 & 3 its the coil packs

if you get it on 4 5 6 then is your sensor.

DaveOx

Is the 'short to ground' code for sensor 2 (17866) related to any of this? Is it the same sensor as 'bank 1'?

Ginga52

did you sort out the issue with EGTs?

DaveOx

The solution was to replace both EGT sensors. It would indeed seem that faulty EGTs can cause misfires, possibly by dumping too much fuel on that bank. I am assuming if the EGTs aren't doing their job, or the signals are impossibly out of range, the ECM will go rich to avoid damage.

I tried swapping coil packs side to side but of course it didn't throw the code then and I couldn't wait for it to do it again (my wife's car and didn't want her staring at the CEL every day) so I went for the EGTs.

Side note - I was getting other intermittent misfires and found that cleaning and excercising the plugs at the ignition module connections (on top of the air box) seemed to solve that.

Ginga52

that's interesting - glad you solved your issue

seems mine are not over yet

i started with these codes:

16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-00 - -
16685 - Cylinder 1: Misfire Detected
P0301 - 35-00 - -
16687 - Cylinder 3: Misfire Detected
P0303 - 35-00 - -
16686 - Cylinder 2: Misfire Detected
P0302 - 35-00 - -
17536 - Fuel Trim; Bank 1 (Mult): System too Lean
P1128 - 35-00 - -
17538 - Fuel Trim; Bank 2 (Mult): System too Lean
P1130 - 35-00 - -
17862 - Exhaust Gas Temp Sensor 1 (G235): Short to Ground
P1454 - 35-10 - - - Intermittent
16688 - Cylinder 4: Misfire Detected
P0304 - 35-00 - -
16690 - Cylinder 6: Misfire Detected
P0306 - 35-00 - -
16689 - Cylinder 5: Misfire Detected
P0305 - 35-00 - -
Readiness: 0010 1001

---

i replaced the MAF and then got these: (after a few runs)

10 Faults Found:
17863 - Exhaust Gas Temp Sensor 1 (G235): Implausible Signal
P1455 - 35-10 - - - Intermittent
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-00 - -
16685 - Cylinder 1: Misfire Detected
P0301 - 35-00 - -
16687 - Cylinder 3: Misfire Detected
P0303 - 35-00 - -
16686 - Cylinder 2: Misfire Detected
P0302 - 35-00 - -
16826 - EVAP Emission Control Sys: Small Leak
P0442 - 35-10 - - - Intermittent
16690 - Cylinder 6: Misfire Detected
P0306 - 35-00 - -
16689 - Cylinder 5: Misfire Detected
P0305 - 35-00 - -
17536 - Fuel Trim; Bank 1 (Mult): System too Lean
P1128 - 35-00 - -
17538 - Fuel Trim; Bank 2 (Mult): System too Lean
P1130 - 35-00 - -
Readiness: 0010 0001

----

i then replaced the pass side EGT sensor 1. Now I have these codes that won't go away:

Chassis Type: 4B - Audi A6 C5
Scan: 01 02 03 06 08 15 16 17 18 34 35 36 37 45 55 56 57 65 67 75
76 77

VIN: WAUYP64BX1N143536 Mileage: 161170km/100146miles
-------------------------------------------------------------------------------
Address 01: Engine Labels: 078-907-551-AZA.lbl
Part No: 4Z7 907 551 M
Component: 2.7l V6/5VT G 0001
Coding: 06752
Shop #: WSC 01312
WAUYP64BX1N143536 AUZ7Z0A1796956

2 Faults Found:
17536 - Fuel Trim; Bank 1 (Mult): System too Lean
P1128 - 35-00 - -
17538 - Fuel Trim; Bank 2 (Mult): System too Lean
P1130 - 35-00 - -
Readiness: 0010 1001


---


I am a bit at a loss... where do i go from there?

Although no codes are shown on the MIL, cylinder 6 has a lot of misfired at idle (how much is a lot by definition??? I am seeing 6 to 12 until the misfire reader resets the count)

Not sure what to do and I don't want to go to the dealer...

DaveOx

I think you have multiple issues here. I would say you may have a fuel pressure problem or possibly a bad vacuum leak, or both. Fuel pressure regulation problems could cause intermittent lean and/or rich conditions. An overly rich condition could cause the misfires.

My suggestion is to clear all the codes, start it and let it idle while watching for codes. Codes thrown at idle a usually easier to diagnose as the engine conditions are not changing so much. If I understand them EGTs are watching for overtemps in the cylinders and normally won't ask for a leaner setting, they will only tell the ECU to richen or retard timing, reduce boost, etc. A lean condition is rare and bad for the motor because it means HOT. Drive gently until you solve this.

Lastly you may want to start a brand new thread on the forum with this issue, possibly even cross post to the 2.7T forum as well. Not everybody would be watching this thread.

Good luck. Codes suck.

Ginga52

Thanks DaveOx
I have another thread in the 2.7 going on right now and I just posted my next steps of may be replaceing the PCV and the spider hose, as per other threads I was able to find in the forums and suggestions from other users. The lean codes seem to be intermittent as I took the car twice in the last two days and no codes came up however the car is rough at idle (almost seem to want to stall especially on a cold start) and then the car is rough/stumbles during accelearation almost like it does not want to boost (although I am not sure this is the right description for you to picture the symptoms or if there is enough details). If you have more ideas let me know.

What's involved to diagnose a bad fuel regulation?

Someone mentioned to me doing a boost test. Do I need special tools?

Thanks for the tip to take easy on the throttle until i get it solved, i did not know this meant HOT in the engine.

Cheers,

DaveOx

Rough idle usually means a vacuum leak. If it runs well once you're off idle, but seems to have varying boost as you accelerate (sort like it is lunging) then that can also point to vacuum issues, since that is what controls boost pressure, diverter valves, etc. It's not always the case, but since you are seeing such weird codes I'd start there first.

Once you've corrected any vacuum issues and verified you have strong spark then you can start looking at fuel pressures and injector health. Make sure you aren't seeing any codes from the ignition modules, as that can cause full banks to misfire (at least in my experience).

Ginga52

after a vaccuum/boost test it seems I have no leaks whatsoever... I changed the MAF, twice... ;-(

I will start another thread with a possible issue with the APR tuning that was done on the car and when all my issues started.