# Audi 2.7T A6 - Bad EGT sensors - Power dips surges....



## masboykie (Feb 24, 2004)

Hi
I was wondering if I am the only person out there with this problem... 
I find it very hard to believe...
As the topic states, the vehicle in question is a 2002 Audi A6 with the 2.7T motor. The car actually got on the road in 2001, so we can say it's been running for about 4 years and a bit (give or take 30K on the odo). I had the GIAC software in it for a while, but I was getting "power drops or dips" in chip mode. I checked for boost leaks, replaced both bad BOVs, also replaced the N75. no change…obviously I could not take the car into the dealer due to the warrantee and the chip... I contacted GIAC and they suggested I have the speed shop check the car out. 
The tech and I “reset” the ECU. We tried everything to get the car to set readiness, but we could not get the CATs hot enough. After looking in the Bentley, we found that the EGT sensors are registering only the default value of 945 degrees Celsius. To make sure, we also checked the wiring and everything was fine. This meant they were bad… I had to take it into the dealer. On my home from the car set readiness…. Which was great, but still did not make the EGTs operations! I took the car out again (to make sure), and ran the EGT testing sequence with the same result. The EGTs never registered anything over 945 degrees (or under for that matter). According to the Bentley they need to reach at least 980 degrees for the test to start. By the way that is damn hot! To get the temp up there, you need the car in full throttle and the rpms between 5.5 and 6.5K! Sounds brutal I tell you! 
I wanted to be sure so I checked with Ross-Tech about the data we were looking at. They confirmed that what we see with our Vag-Com is what the dealer would see with their equipment.
This is where it got frustrating...
So, I set up an appointment to get the car looked at, by the dealer. Unfortunately the car “threw a code” the morning of the appointment (3rd time it’s done that in about 2 months – others I reset). When I got to the dealership they were not interested in looking at the EGT problem. The only thing they wanted to look at was the "random misfire" code. Eventually they blamed the code on 2 bad spark plugs, that were “severely clogged”, to quote them. How could this be? The car had it’s 40K service less than 3000 miles before! Anyway, I was told they “ran across bad plugs” all the time… This sounded like “crap” to me… but who am I to argue…
I took the car home and ran the EGT sequence… same result… 945 degrees. Has anyone else had “misfire issues” that eventually was found to be caused by bad EGTs? On this car these puppies are expensive! +/- $800 for the two (I think), so I am sure they will “dodge that bullet” if they can.
Next…. As part of the “plug job” I complained about the right turbo getting too noisy…It turns out I had to get the turbos replaced (thank God for the warrantee). After the Turbo job the car set readiness, so as far as they were concerned all was well…. Please note I specifically asked them to check the EGTs before they did this, so we could “kill two birds”… in one ear out the other… as my dad used to say.
I made a “deal” with the service guy… I told him that I would pay for the diagnostic time, if they find that the EGTs were NOT bad. The car is scheduled to go in for a checkup in a couple of weeks (after the turbo job) so I will get them to do this then. I will update this thread then…
Anyone out there with the technical knowledge
Can these bad EGTs be partly or wholly to blame for the bad plugs and turbos? If I think about this logically, they are supposed to inform the ECU what the exhaust temp is at the turbos, so the mixture can be adjusted, right?…. If they are always sending a default value, could this not create excessive heat in turbos and exhaust, CATs etc? Without the ECU “knowing” about it? Or am I totally off base here? This cannot be good in the long run, right? As for the whole design… I think this is the stupidest thing I‘ve ever heard off, on Audi’s part… If they use this default value… how will they ever know the EGTs have gone bad? I write software for a living and that logic simply makes no sense!
I would greatly, appreciate if someone with a real understanding of this “stuff” could elaborate? I am sure it will be beneficial to a lot of people.
Thanks in advance!!
Cheers
Masboykie


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## MarcoVR6SC (May 3, 2003)

*Re: Audi 2.7T A6 - Bad EGT sensors - Power dips surges.... (masboykie)*

If the sensors are bad, they should throw an error code. In addition, that the two sensors or bad at the same time is not very likely.
For info, the EGT sensors are connected to small adaptors each, not directly to the ECU. Maybe they could be faulty.
I would rather think of one or more bad spark coils, a bad coil driver (one per bank), or bad connections in the wires/connectors.
Having miss fires can be the reason why you do not reach 980°c.
Good luck.


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## masboykie (Feb 24, 2004)

*Re: Audi 2.7T A6 - Bad EGT sensors - Power dips surges.... (MarcoVR6SC)*

Hey MarcoVR6SC
Thanks for the info.
Looks like testing the EGTs is not as simple as they make sound in the Bentley? Why did they not mention the "adapters" you are referring too?
We were able to measure directly from the EGT's harness connector to the ECU, when we were checking the wiring. Unless the adapter you are talking about is "in" the connector iteself... that the harness connects too. ...if that makes any sense... 
The EGT sensor wiring is not exposed and I do not want to cut it to check continuity through the connection. This will probably void my warrantee claim.
I'll have a look and post the results.
Cheers
Masboykie


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