techy101

Hey all,

I'm hoping someone on here can offer some advice. I did a carbon cleaning (using THIS guide) the other week and have run into a problem. A couple of days after I finished the cleaning I noticed that the car had trouble turning over. It would start then the RPM's would bog way down, the car would shudder a bit, then it would return to normal.

In the two weeks since the problem has gotten progressively worse. Now the car starts, but then shudders for a minute or so of revving before finally returning to normal. When this ends it runs butter smooth and I have no more issues.

The problem only seems to occur when the car gets hot sitting outside. On colder mornings it fires up without a problem. I'd thought maybe I didn't hook a fuel line up tightly enough or something so took the upper intake off again and disconnected/reconnected the fuel rails again and reassembled everything. Unfortunately this made no difference.

I would appreciate any help if finding the mistake that I made.

techy101

I forgot to mention, this is a 2007 A6 Avant 3.2L with 155k miles.

KnappAttack

Fouled spark plug.

techy101

I forgot to mention that I'd also replaced the spark plugs as a first attempt at a fix, but it didn't help.

royclark

Do a VCDS scan, this should tell you what the problem is.

allenst

did you do plugs ?
if yes, sometimes a reused coil can be the issue due to fitting inside

hrc4u

+1 to what Roy said.. Get a Vcds scan!
Could be a bad coil.. Will show up in scan.. Audi have lots of issues with earlier coils..

KnappAttack

Not sure what engine you have, but I wonder if an idle air control valve is sticking perhaps?

Surging idle would point to a sticky control, whether thats a IAC valve or throttle butterfly, I'm not sure.

But if its missing and not firing on all cylinders, that would point to a plug or coil.