- Buick Ownership
- 2001 Century Custom
So, a couple weeks back, starting the car to head home from work, it was running really rough unexpectedly. Get it home, hook up the scanner, and was getting P0300. So, idle is rough, light acceleration is really rough. Picking up speed and running at higher RPMs it runs more smoothly. And it also seems to be chugging gas. I thought at first it might be the fuel pressure regulator, but after finally being able to replace it, no change has occurred. The EGR, plugs, wires, coils, ICM were all replaced in 2016. So maybe it's a vacuum issue? I mean, it seems fairly similar to when I accidentally cracked the plenum and caused a vacuum leak, just nowhere near as severe (I broke off a fairly large chunk from the corner, and it would only start and stay running with a lot of open throttle). But there isn't a whole lot of anything that seems to be connected to vacuum, and it all looks ok at a glance, so not sure what needs to be checked next. I was thinking I would test the vacuum off the test port, but I don't know if my work with older carbed motors is clouding my judgement, since it's running so rough I'm not sure it would be making good vacuum in the first place.