Help please!!
 

2006 A6 4.2 91K miles

CEL light flashing upon start up and engine shaking. Shop is saying they want to tear-down inspect the cylinder head for $6K to $7K. Really?

and the txt description from the shop:

Pulled fault codes:
16684 RANDOM/MULTIPLE MISFIRE DETECTED
PO300 001 MIL ON
16685 CYLINDER 1
PO301-001 MISFIRE DETECTED MIL ON
16687 CYLINDER 3
PO303-001 MISFIRE DETECTED MIL ON
16686 CYLINDER 2
PO302-001 MISFIRE DETECTED MIL ON
16688 CYLINDER 4
PO304-001 MISFIRE DETECTED

Text written on invoice:

"CHECKED IGNITION COILS, OK AT TIME INSPECTED. CHECKED SPARK PLUGS, WORN BUT NOT THE CAUSE OF THE MISFIRES. CHECKED LOW SIDE FUEL PRESSURE, OK. CHECKED RUNNING COMPRESSION, 150 PSI. CHECKED FUEL INJECTOR PULSE, OK . REMOVED INJECTORS AND VERIFIED GOOD SPRAY PATTERN. PERFORMED LEAK DOWN TEST ON CYLIDER 1, CYLINDER HAS VERY LITTLE LEAK DOWN. CHECKED BACK PRESSURE ON BANK 1, OK. CHECKED SPECIFIED VS ACTUAL CAMSHAFT TIMING, OK.
NEXT STEP WOULD BE TO PERFORM TEAR DOWN/INSPECTION OF CYLINDER HEAD AND TIMING CHAINS. INTAKE VALVES ARE NOT CLOSING ALL THE WAY CAUSING POSITIVE PRESSURE INSIDE THE INTAKE MANIFOLD.”

Thank you so much for looking at this problem and offering your advice.

I dont understand how they can think its internal when they did a compression test and leakdown test and it passed. You may want to try another shop thats comfortable with European cars.

I would look for large a intake leak, There are bulletins on the 4.2 intake manifiolds loosening up and causing misfires. Also failure of the crankcase vent valve can cause a huge lean condition and misfire and shaking. There are so many possibilities from connections to wiring and even the ECU. The shop doesnt seem to have the knowledge to test much further than the more basic things.

Thank you Prospeeder. I will take a look at the intake manifold bulletins. Agree with you about the shop.

Was there any resolution to your problem?