Had a 2008 Civic come in with a rough idle that cleared up after I cleaned the throttle body

The car was shaking pretty bad at stoplights, and the owner said it had been getting worse over the last few months. I pulled the throttle body off and it was caked with black carbon, maybe a quarter inch thick in spots. After a good scrub with some cleaner and a new gasket, it idled smooth as new. Has anyone else seen a throttle body get that dirty and cause such a big change in how it runs?

2 comments

2 Comments

the_olivia1mo ago

Wait, are you sure the throttle body was the only problem? I've seen that kind of buildup before, but usually there's something else going on to cause it, like a bad PCV valve letting too much oil vapor back into the intake. Cleaning it might fix it for now, but if the root cause is still there, the gunk will just come back in a few thousand miles. It's worth checking the rest of the system while you're in there.

campbell.logan1mo ago

Oh man, @the_olivia is totally right. I cleaned mine once and it was a mess again so fast. My old Civic was just drinking oil through a bad PCV valve, I swear. I ended up having to clean the whole intake manifold, it was coated in this nasty, sticky film. Felt like I was just doing the same job twice.