I'm trying to locate the mass airflow sensor because I think this may be the cause of my rough running forester. But I've checked online and can't find a diagram of where it is on my car. I found a device that I thought was it on the throttle body area- when I pulled it, it looked like a metal mushroom and no sign of wires. It was dirty so I cleaned it, but I don't think it is the MAF. Maybe I don't even have one?

 

I dumped half a can of seafoam in the gas, and now I'm going to seafoam a vacuum line.

 

Thanks for any healp and/or diagrams.

 

ironandsteel

MAF sensor will be the little box in the intake tube right by the air filter housing. http://m.instructables.com/id/How-to-check-and-change-a-Mass-Air-Flow-Sensor-for/

2002 may not have one.

 

The mushroom thing you found on the throttle body is the Idle Air Control Valve. Those do occasionally need to be cleaned, so you've definitely done some good for that.

 

Rough running can be caused by many things though. Do you know anything about the maintenance history? Always good to start with a fresh set of NGK spark plugs and wires, air and fuel filters, and a fresh Subaru PCV valve.

A couple months ago it threw a cyl 4 misfire CEL, and sure enough, the #4 plug wire had a visible crack. So- new wires are done. I just now cleaned the air filter with compressed air- it wasn't too bad. Gotta figure out where the fuel filter is. PCV probably a good idea too. I think I know where it is- it has a 3/4" short curved tube that connects to the throttle body.

 

I've had the car since 40k miles and it is up to 120k now. 

 

Thanks-

Did you change the plugs when you did the wires?

Have you had the timing belt changed? You're 2 years and 15k miles overdue for it.

No, not changed plugs, but I will tomorrow. Yes, I had the timing belt changed around 110k.

 

This afternoon I did the seafoam vacuum line smoke show. I also added half a bottle of "star tron" magic potion, to the tank. I then took it out and drove it hard. I think it is better- it seems to idle smoothly now, but I'll go ahead and do plugs anyway. Do I need to get a PCV from Subaru? Or can i get a good one from napa or advance auto?

 

This is a somewhat unusual forester- it has the manual transmission, but it is fully loaded- sunroof, etc. You pretty much never see this combination- I snapped it up as soon as I found it. I really like stick shift. It is a shame that a limb fell on this car's roof a while back- made small dent. Doesn't affect the sunroof operation tho.

The parts store PCV valves can cause more problems than they fix. Oil consumption, idle problems, they also clog easier and wear out faster.