Only P0506 and Cylinder Misfires (Rough Idle + Stalls)

[Blockis]

Hey there Q5ers! I'm usually over in the B7 A4 group, but my parents have a 2011 Q5 (2.0T, Auto) with 230k miles and I'm stumped on some recent codes.

Initially, the car had a P008700 (fuel rail / system pressure - too low) and it would intermittently stall or not start. We didn't see any obvious signs of leaking or anything, but we replaced the HPFP and checked the cam follower (looked great, no scoring or anything, it looked pristine).

Now the P008700 code is gone (woohoo!) but I see new codes:

• P0300 - Random/Multiple Cylinder Misfire
• P030X - All Cylinders misfiring
• P0506 - Idle Control System RPM - lower than expected

It would appear that the cause of the P0506 is why the cylinders are misfiring. I have no other codes. What should we be checking next? Fuel injectors? Vacuum leak - how would we test when the car can't idle for more than 10 seconds before it stalls and dies? Throttle body cleaning? What can we do to try to narrow down what it might be?

I saw a video of a Tiguan with a similar issue (only misfires + P0506) and the guy suggested disconnecting the PCV from the intake manifold and just covering/blocking the hose port on the intake manifold -- if the car starts to idle normally, then that would be indicative of the PCV valve being bad. Thought that was interesting, as we did replace the diaphragm in the PCV valve about a year ago, but not the whole unit. We did the test, and it still died even covering/blocking the port.

Thanks y'all!

[Spike00513]

check LPFP

[Blockis]

check LPFP

Is there a measuring block to observe before ripping into it?

[Blockis]

Took to a shop, they did a compression test, and found that cylinder 2 had no compression. Their recommendation is a valve job for $3,500 — is this something I can do as a project (no timeline) or is this better left to the pros?

[QwertyD]

You check your injectors yet?

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[Blockis]

You check your injectors yet?

Sent from my SM-N986U using Audizine Forum mobile app

I have not, currently not with the vehicle. I'll have the folks try to start it up with a screwdriver on each injector and listen for inconsistent or lack of ticks.

Or is it possible the o-ring for one of the fuel injectors went bad? Probably too hard to tell without ripping her open lol.

If a valve job is needed, feels like it would be timely to replace injectors and o-rings while you have so much off.

[MSq5]

A leaking injector seal, injector body, or leaking valve seal can cause zero compression.

I'd also want to scope tge cylinders, especially tge one with zero compression to see what they look like.