What is this thing

[Aussiecanyoncarver]

Hi I am having a look at my fuel system in my car as it seems to jerk around and stutter in low RPMs but runs fine at high RPMs, as I tinker I notice this black round thing, I assume it's for fuel, but it has no fuel in it. I have a 1993 GC8 Subaru Impreza wagon. Is this bad, and how do I fix it?

Edited August 14, 2016 by Aussiecanyoncarver

[Aussiecanyoncarver]

It's on the left hand side closest to the lights, sorry if the picture doesn't load

[987687]

That's the evap canister, it's full of charcoal. Instead of venting to atmosphere, the fuel tank vents into that when the car in shut off. It catches fuel vapors and the engine sucks them in on startup. Unless the solenoid going between that and the intake manifold is stuck open or one of the vacuum lines is broken, that's likely not the cause of your problem.

[Aussiecanyoncarver]

That's the evap canister, it's full of charcoal. Instead of venting to atmosphere, the fuel tank vents into that when the car in shut off. It catches fuel vapors and the engine sucks them in on startup. Unless the solenoid going between that and the intake manifold is stuck open or one of the vacuum lines is broken, that's likely not the cause of your problem.

Ok that's one less thing checked off, would you have any idea as to what it may be

[987687]

I honestly don't know a whole lot about the obd1 subarus. I would check the throttle position sensor (TPS) with an analogue volt meter, though. As you open and close the throttle, the resistance should change with a smooth sweep, not a jerking motion of the needle. Think of an old scratchy volume knob on a radio. That's what can happen when they wear out. It's definitely something that can cause jerkyness at low throttle application.

 

Other than that, the usual suspect things that cause a car not to run well. Check/replace plugs and wires, do a compression test.... Drive with a heavier foot.

 

I'll let someone who knows more about how these work chime in.