it's an 2002 L200 saturn, threw a p0410 code and a p0300 code. replaced the small vacuum lines going to the check and diverter valve which cleared the p0410. now it still has the random misfire code and runs horribly -IF- the hose from the air pump is plugged into the airbox. IF NOT plugged in it will idle properly. I unplugged the check valve and tested it with my volt meter and it is getting current. I've also held my hand on the air pump and it does turn on and pump air. Also thas new spark plugs and the coil pack was tested along with the control module and they didn't fix it. HELP

 

Not plugged in and the air cleaner hole is plugged or left open? How does it run if the air pump is not running?

 

Its open, I've plugged it with my palm and it didn't seem to change anything. When we had it idling the air from that hose was always blowing out. Is there something likely to make it stay on and could that be the issue?

 

If the check valve on the exhaust side fails you might have EGR at idle and the misfire. I just replaced my check valve because it cracked and created an exhaust leak. The hose is the air inlet for filtered air the the smog pump, there should never be air coming out of the hose.

 

are you talking about the valve on the top canister where that connects to the steel tube into the exhaust manifold or the small check valve with the two vacuum hoses mounted on the side of the engine

 

yessir, it was the valve. Though it isn't throwing the missfire code. Shes hesitating to shift now in second, and doesn't seem to want to step down for like the passing gear acceleration. No codes though, I'm suggesting they have the transmission serviced. I don't think it's related but could be wrong

 

It attaches to the steel tube that bolts to the manifold. It takes a 7/8” wrench maybe. It is a one way check valve to only let air into the exhaust. If you take the 3/4” heater hose sized hose off nothing should blow out.

 

Now it sounds like a throttle position sensor giving you problems. I would clear the codes and take the car for a nice ride so everything can relearn how to drive properly and see what comes back.

 

still shifts funky in second, will go up to 4k and not want to shift unless you let off the gas

 

Will it upshift at light throttle? What seems like transmission problems can be a plugged fuel filter.