Intake Manifold Flap Issues Causing Power Loss in S10?

Had almost identical symptoms with my S8 Diesel 2016. The engine misfire and performance issues started gradually, first just a slight hesitation, then got worse with that characteristic hissing sound you mentioned. The airflow control system was acting up due to a faulty intake manifold flap control. Got it diagnosed and fixed at a workshop after trying basic troubleshooting. The repair bill came to 465 for parts and labor. Since the fix, engine performance returned to normal and fuel economy improved significantly. Quick question, have you scanned for error codes? Also, when exactly did you first notice the hissing sound? These details could help confirm if you're dealing with the same intake system issue I had. Would be helpful to know: Current mileage, Any error codes showing, When symptoms first appeared, Any recent maintenance done, Does it happen more during cold starts? Let me know these details and I can share more specific insights from my experience.

Thanks for sharing your similar experience. I'm at 107531 KM and just had the regular service done last month. Started noticing issues about 2 weeks after that service actually. The hissing sound began subtly but got more noticeable within days, especially during acceleration. No engine light yet, but I did get a scan done showing a P2015 code related to the intake manifold flap position sensor. Cold starts seem normal, the problems kick in mainly after the engine warms up and under load. Interesting that your repair cost was reasonable, gives me hope this won't break the bank. Was your fix pretty straightforward or did they have to dig deeper into the intake system?

Yeah, your symptoms match exactly what I experienced, especially that P2015 code and the hissing getting worse during acceleration. Sounds like we're definitely dealing with the same intake manifold flap control issue. My fix was pretty straightforward, the workshop mainly focused on the intake manifold flap control mechanism. They didn't need to tear into the deeper parts of the intake system. The reduced power and rough running cleared up as soon as they replaced the faulty components. One thing I noticed, the hissing and performance issues got way worse when I waited to fix it. The longer you run it with compromised airflow control, the more it affects overall engine performance and fuel economy. Quick tip based on my experience: make sure they check the actuator motor and linkage while they're in there. Mine had some wear on the linkage that could've caused the same problem again if they hadn't caught it. Been about 8 months since my repair and everything's still running perfectly, no more hissing, normal power, and fuel consumption back to standard. Worth getting it sorted sooner rather than later.

Thanks for that detailed feedback. Really helpful to hear your repair turned out straightforward and lasted well. Good tip about checking the actuator motor and linkage, I'll definitely mention that when I take it in. I've already booked it at the workshop for next week. The symptoms are getting worse daily, especially that hissing and reduced power during acceleration, so I agree about not waiting too long. Plus, I don't want to risk more engine performance issues by leaving it. Your experience gives me confidence it's the intake manifold issue we suspected. At least it's a known problem with a proven fix, and the repair cost sounds reasonable. I'll update once I get it sorted. Thanks again for sharing such specific details about your experience with the same problem. Really helped confirm what I'm dealing with.