Q5 Diesel: Rough Running + Power Loss Points to Intake

Had exactly these symptoms on my 2017 Q7 TDI last season. The engine misfire and performance loss turned out to be a cracked intake manifold with multiple vacuum leaks. The rough idle and strong exhaust smell were dead giveaways. The manifold had developed hairline cracks from heat stress, creating air intake issues that threw off the fuel-air mixture. This caused the engine performance problems and triggered the check engine light. It was quite serious, running the engine in this condition risks further damage to other components. The fix required complete manifold replacement along with new gaskets and vacuum lines. The engine needed thorough diagnostics first because vacuum leaks can be tricky to pinpoint. Labor intensive job since they had to remove several components to access the manifold properly. Your symptoms match almost exactly what happened with my Q7. Would strongly recommend getting it checked soon, as continued driving with vacuum leaks can lead to more expensive repairs down the line. Note that parts availability might affect repair time, so best to have this looked at by a shop that regularly works on these engines.

Thanks for sharing your Q7 experience. The symptoms you described match my Q5 issue perfectly, especially the rough idle and vacuum leak indicators. I went ahead and had it fixed, it was indeed a cracked intake manifold causing major engine performance problems. The gasket leak around the manifold made the diagnosis pretty straightforward once they got in there. Can you recall approximately how much you paid for the complete repair? Also curious if youve had any related issues pop up since getting it fixed? My check engine light hasnt returned yet but wanting to stay ahead of any potential problems.

Thanks for the follow up. Since getting the intake manifold replaced on my Q7, the car has been running perfectly with no engine misfire or performance issues. The repair cost me 1180 Euro total, which covered the new manifold, gaskets, and labor to fix the vacuum leak properly. The check engine light never came back after the fix, and the engine runs smooth now without any of the previous symptoms. No more rough idle or exhaust fumes. The shop found the manifold was pretty badly scorched, which caused the gasket leak and vacuum problems. Its been about 8 months since the repair and I havent had a single related issue. The key was getting it fixed as soon as the symptoms appeared, preventing any cascade of problems that could have made things much worse and more expensive. If your repair was done thoroughly like mine was, you shouldnt expect any further problems. Just keep up with regular maintenance and youll be fine.

Thanks everyone for your insights. After reading about the similar experience with the Q7, I took my Q5 to a specialist shop last week. The manifold pressure tests confirmed a major vacuum leak caused by both a cracked intake manifold and deteriorated gaskets. The total repair came to 1350 Euro, which included replacing the manifold, all related gaskets, and some vacuum lines that showed wear. More than I wanted to spend, but the engine misfire issues were getting dangerous. Been driving it for a few days now and what a difference, no more jerking, stalling or rough running. The exhaust fumes are gone and power is back to normal. The shop did a thorough job checking everything while they had it apart, so hopefully this fixes it for good. Really glad I got a second opinion instead of going back to the first mechanic who missed these obvious signs. Sometimes paying a bit more for experienced techs who know these engines is worth it.