sjs1978

First symptom when everything first started - check engine light flashing and engine shaking slightly several times while decelerating during drive to work.

Brought to dealer right away, they took unusual amount of time to diagnose problem. Said there was a misfire on cylinder 1 and 3. They followed some steps to check various possible causes. Finally said ti was carbon buildup causing the problem and told me to do the carbon cleaning.

Fault codes were : P0300, P0301, P0302, P0303

I paid ($950) for the carbon cleaning + service time. When I picked up the car, the car ran smooth, seemed ok.

When I started it up the next morning, it was shaking but didn't think much about it. After I left my driveway it ran smooth, so I just attributed it as a temporary side effect of the recent repair and assumed it would go away.

for several more days It was shaking again on startup but run smooth during driving.

Today when I pushed the engine start button it seemed to take a bit longer to start up, and it was shaking even more on startup. But it drove smooth for most of the trip.
But all of a sudden check engine light started flashing and the engine started shaking again. I would accelerate and the RPMS would go up and down and then back up again like it was losing power for a moment but then it would stabilize as it gained power. Every time I stopped at a stop light, the car would start to shake really bad and I thought it would stall or shut down. But when I start driving again and bring the rpms up, the shaking goes away. Finally the check engine light stopped flashing and remained on. I was close to the dealer and managed to drive to the service bay.

EDIT:

Got the result of the diagnosis
Same codes as above
Fault codes were : P0300, P0301, P0302, P0303
Plus a new one P2177

They want to charge $350 (cad) to replace the Purge Valve.

What should I do?

I think in total this is too much money when the problem potentially had nothing to do with the carbon deposits. I may not have needed to do the cleaning to fix the problem directly.

[2010 Audi A5 2.0 TFSI - CAEB]

Saadtec

My friend has a similar problem. Have diag. vacuum leak at the PCV tube in the intake. Fixing that and the PCV diaphragm first, then replacing the injectors (we already replaced the spark plugs and checked the coils). Your problem lends itself to injectors based on the fact that the "cleaning" helped.

Directed injected engine get tremendous amounts of carbon build up.

You do not need the whole PCV, just the diaphragm. Rock Auto for $20. Simple to replace. To check, start the car and spray brake clean around the area to see if the idle raises. If so you have a vacuum leak which leads to a lean condition that can cause misfires

Will keep you updated on our progress

sjs1978

And yet every time I bring up the fuel injectors to the dealer they keep saying, 'No, no, thats not the problem.' Is there a specific engine code that indicated fuel injector issue? Or is it a diagnostic process (swapping components) that reveals this?

Saadtec

Not sure as to why they are so adamant about it not being an injector but were willing to charge you for cleaning them. Our local dealer has also confirmed an injector but I always like to fix known problems first before spending a bunch of money as a vacuum leak can cause a lean condition which can also cause misfires.

To my knowledge there is no way for the ecu to know that the injector dispensed the proper amount of fuel into the combustion chamber unless they have individual EGT's (exhaust gas temperature) per cylinder or internal sensors in the combustion chamber. There may be a code for resistance or short to ground/power but that is not the issue we are seeing. It's the fact that the injectors are gummed/clogged up with carbon and that carbon can actually affect/block the amount of fuel being delivered to that cylinder. At idle it becomes more apparent as the injector pulse width is very low so it does not take much to block the flow of fuel

Saadtec

I should say that the dealer technician suspects and injector. The owner opted not spent the $150 diagnostic fee for conformation

Planoguy

So what was your out come ? Did you ever determine the root cause of your issues ?