Low compression on one cylinder

I picked up a 2007 Saturn Ion for scrap money with a bad clutch. I swapped out the clutch and all is well in that department. I pulled a P0304 code from the computer so I started troubleshooting a cylinder 4 misfire. Plugs good, coil good, injector firing. Checked the compression and it's sitting at 50psi. Other three cylinders are good. Drop a bit of oil down the spark plug hole and get about 52psi so I'm guessing it's a valve. What I don't understand is how well this thing is running. It's a basic 2.2l Ecotec. The idle is smooth and it pulls well for what it is. Every time I've had a cylinder that was this low the engine was shaking like crazy and chuffing out the exhaust. It just seems weird.

I can pick up a low mileage used engine, with warranty, for around $300 so it probably isn't worth my while to pull the head and investigate but I'll likely do it anyway.

Just drive it. Maybe pull the valve cover and make sure it isn't something stupid. If you pull the head you'll probably end up sucked into the thing and spend more than the $300 you budgeted for an entire engine fixing the one you have.

saturns were built in a way that defied GM.. you couldn't kill them.

Kenny_McCormic wrote: Just drive it. Maybe pull the valve cover and make sure it isn't something stupid

If I could I would but it has to pass an emissions test before I can register it. I'll double check the valve clearance before I pull the engine. It could also be a head gasket but there are no other symptoms so I doubt it.

I also just noticed that I became a HalfDork

In reply to Wayslow:

Carry on then.

Pull the valve cover. I've had 2 low compression enginesnow that were a broken valve spring. Easy $8 fix both times....