C70 Vacuum Leak Manifold Pressure Sensor

Whoa, sounds like a drag! A manifold pressure sensor, huh? It's like the canary in the coal mine for your engine – super sensitive to changes. Reduced power and bad mileage screams sensor alright! Is it just a hunch, or did you try cleaning it or something? Maybe check for obvious cracks or loose hoses around the intake manifold first?

Thanks for the quick reply! I haven't tried cleaning it yet, but I did give the hoses a quick visual check. Nothing obvious jumped out. Where exactly should I be looking for these vacuum leaks? Any specific spots that are more prone to issues on the C70?

Alright, so you know how when a doctor can't quite figure out what's wrong, they run a bunch of tests? Vacuum leaks are kinda like that. They can be sneaky! Since you didn't see anything obvious, and with those symptoms, a dodgy sensor is highly probable. You could try spraying some starter fluid around the intake while the engine is running (idle will change if you find a leak), but honestly, at this point, I'd just bite the bullet and take it to a workshop. They'll have the proper diagnostic tools to pinpoint the issue and replace the sensor if needed.

Took your advice and went to a shop. Turns out you were right – large vacuum leak leading to a faulty manifold pressure sensor. They replaced the sensor and fixed the leak. Cost me 235€, but the car's running much better now. Thanks for the help!