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AudiDoc, Independent Audi Shop Owner
Category: Audi
Satisfied Customers: 1695
Experience:  I've been working on Audis since I was 18 and own an independent Audi repair and performance shop
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I started with a CEL about 2 months ago, and a local indy

Customer Question

I started with a CEL about 2 months ago, and a local indy shop (highly respected VW Audi shop) diagnosed a vacuum leak. They recommended patch (not replace) the line. We did and the CEL came back about a week later with a rough idle. Indy shop said it was misfires on cylinders 5, 6, 7, and 8 from carbon. Recommended carbon cleaning, new coils, and plugs, as well as fuel cleaner for injectors. I took it home and did a full carbon cleaning, new coils and plugs for that bank, and now the car runs worse than ever before. It went from a rumble like a cold muscle car on start, to now it sounds like a bag of bricks being tossed around under the hood. Roughness does go away over 1500 rpm though. I have only driven down driveway and back since repair because of rough running.
JA: Does the light stay on, or does it blink?
Customer: blinks at startup then solid
JA: What is the model/year of your Audi?
Customer: 2007 Q7 with 4.2
JA: Are you fixing your Q7 yourself? What have you tried so far?
Customer: So far the indy shop did the vacuum leak repair, I had a different shop do carbon cleaning, and I did plugs, coils and fuel system treatment (audi spec fuel addictive)
JA: Anything else you want the mechanic to know before I connect you?
Customer: Nope
Submitted: 10 months ago.
Category: Audi
Expert:  Wolfgang replied 10 months ago.

Thanks for choosing Just Answer . I'm Wolfgang here to help!!

I am confident we can resolve your problem together. Please
understand that I don't know your skill level. In most cases when you have a problem
with the way the vehicle performs, specialized tooling is required to acquire computer
data/information or engine testing results. We didn’t build these complicated vehicles; we
just diagnose and fix them. Also understand that I can't see, smell, hear, or touch the
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Below is my first answer or request for more information. If you do not understand it, or you need more information from me, or need me to go in more detail.

the carbon cleaning i'm worried about of how did they do that exactly. do you know?

please let me know!!


Customer: replied 10 months ago.
Thank you for the response Wolfgang! Just a quick background on me, as I understand you are working blind here. I have done some wrenching on GM cars in the past (basic stuff on an 88 Fiero and 90 Corvette ZR-1 I raced) and now I only really work on my small collection of Swedish cars (a couple Saabs and Volvos). I do not have a lot of experience with Audi/ VW as this is my wife's car, but the plugs and coils are pretty basic plug and play so I felt comfortable to tackle them (just did a set of plugs and coils on my Volvo C70).
The carbon cleaning was done by a shop who uses the new Valvoline Easy GDI cleaning. It is a new process that chemically clean the valves of a direct injection engine, where traditional "in the tank" cleaners would be useless as gas does not wash the valves in GDI engines. The engine did appear to run a bit better right after the treatment, but started running rougher within 100 miles afterwards. Actually makes me wonder if the cats got gummed up by the carbon cleaning.
Anyway, that is how the carbon cleaning was done. Also, I have checked the MAF for that bank and it appears clean, however I have not taken it off to clean it.Look forward to your reply,Nik
Expert:  Wolfgang replied 10 months ago.

OK well lets hope that the cleaner did not burn the cats.

see at the dealer level we use a walnut shell blaster with the intake off clean them that way . musch safer .

what scan tool do you have?

Customer: replied 10 months ago.
I need to get a new one (my six year old took my old one into his pool ...) I can have the local auto parts store run the codes for me for free though.
Expert:  Wolfgang replied 10 months ago.

if you can get VAG COM that would be great need to see values while running more than just codes