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Audi A6 1998-2004, S6 2002 and later, allroad 2001 and later, rs6 2003 and later (C5) Rough Idle, Misfires, Rough runnning.

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Last Post: Sep 24, 2013 12:43 AM Last Post By: mcorbettsr

Posts: 1
Registered: 06/08/13
Rough Idle, Misfires, Rough runnning.
Posted: Jun 8, 2013 11:39 PM
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I'm hoping for some additional insight on my problem.
I was driving home from a customer's house on the highway, when the car suddenly started running rough and misfiring.
I assumed it way my ICMs again, as i'd had similar problems, but I've replaced both ICMs within the last year.

I purchased a Diagnostic cable and pulled codes:

I also pulled 0431 and 0421, but I have had this code from the time I purchased the car, and I've been told it's the sensors being too sensitive.

I checked the fluids, oil was low, so topped it off. I always used full synthetic.
I've played with the MAF, cleaned it and even tried replacing it, to no effect. Unplugging it does nothing to make the car run better.
I found a cracked hose on one of the EGRs and fixed that. I've used seafoam in the gas just in case it was bad gas. I have ICMs under 1 year old on it, and new coil packs and plugs about 2 years old. I pulled coil pack and plugs on two random cylinders, and the plugs are clean, dry and have no damage.
During this time the car felt like it was trying to run normally for split seconds, but now just runs rough all the time. Under heavy acceleration CEL blinks. Runs rough at idle, and both in and out of gear. Fuel economy is a little less than normal. Acceleration is dismal. I smell gas when first starting. The car has always had times when I first start it for it to stall, but starts on the second try.

I've thought about fuel supply (filter, pressure regulator), vacuum lines, and even injectors.
Right now, I cannot afford to have it looked at professionally, and am trying to spend my money most wisely on parts, without blindly replacing everything.
I am planning on replacing the vacuum lines monday, as that is a cheap fix.

Any other suggestions on what would cause this to happen so quickly.

Posts: 1
Registered: 02/09/12
Re: Rough Idle, Misfires, Rough runnning.
Posted: Sep 24, 2013 12:43 AM   in response to: ZeeBorg in response to: ZeeBorg
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I would look at the fuel pump, if it is running rough and you smell gas it could be low fuel pressure, causing the injectors to dribble instead of spraying. There are several things to look at, first is pressure, put a gauge on and flip the key, it should jump up to 58 psi, and hold for 3-4 min without dropping more than 1-2 psi per min, then check for volume, easiest to jump fuel relay so it stays on with key on, you should get 1.5 - 2 cups in 15 seconds. You can also check to see what kind of voltage drop you are getting from the pump. Excessive drop means pump is pulling to much amperage. If yours is outside parameters then replace pump. If you have an A6 Quattro with the 2.7t make sure you have less than 1/4 tank when you pull the pump out or it will overflow the tank onto the ground and you will definitely have a quarter tank then :(
Hope this helps

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