AuidiQ5$

I just acquired a 2012 Audi Q5 with 150,000 miles on it, and while looking over it, I saw a hole in the intake manifold around the #2 piston area. I noticed a significant carbon buildup on the valves after removing the intake, so I gave them all a thorough cleaning. The car experienced an intermittent misfire after the replacement intake manifold was installed, and after driving, the area where the original intake manifold hole was is now getting warmer to the touch than other zones.These are the findings following a check of the compression and spark plugs. After removing the spark plugs, it was discovered that while cylinders #1 and #4 had normal wear, cylinders #2 and #3 showed no compression reading despite numerous attempts. Cylinder 1&4 had a compression of about 130. Do you know why the intake is heating up where the hole used to be, why the spark plug tip broke, and why there is no compression on the #2 and #3 cylinders? Although I'm considering a full engine rebuild, I'd like to know what might have caused these issues first.

SMac770

Why is there no compression on two cylinders? Assume a ring issue or a valve issue. I believe they would normally move from compression test to leak down test to figure out the nature of the lack of compression?

You don't post a pic, so no idea what you're talking about with a "hole" on the IM. We're to assume this is a 4-cyl CAEB engine with the plastic IM?

If you've got no compression on 2 and 3, you're going to have far more than just an "intermittent misfire".

simplesez

Sounds like you bought a project. Just replace the whole engine and flip it. Seems like you would need a laboratory to discover the cause to this effect. It's a hypothesis unless you break it apart for fun.

AuidiQ5$

SMac770

You had some kind of catastrophic failure. Probably timing chain skip. That hole might be something coming out of the cylinder and shooting through it. You probably have bent valves from piston collision. Nothing different from the 2.0T in the B8 A4 and B8 A5, so all those videos are equally relevant.

Have you checked the timing chain measurements?

S4'ed

Wow......I hope you paid about $1 for this Audi....

AuidiQ5$

Notice a peice of the manifold partition plate broke, seems burned, I thought that made the hole

S4'ed

More likely that the upper piston ring-land cracked, or the spark plug electrode cracked (from LSPI), and a fragment was ejected thru the intake valve, through the plastic manifold.
If you boroscope that cylinder, you might see a piece missing from an edge of the piston crown.

AuidiQ5$

Can any one tell me why is it that where the hole was, that spot is heating up to touch, only spot on intake that's warming up

simplesez

I didn't do great in thermodynamics class but it's heat from the engine leaking out. You no longer have a vacuum so the intake is leaking air and that air isn't going to be at ambient temperature.