2008 5MT - Idle Surging When In Gear, Not in Neutral

[afeinstein]

(This about an Outback so I hope this does not offend anyone that I am asking here.)

 

I have an 08 Outback 5mt with just over 100k. Recently it started to do the following whenever the car was very warm (driven over 20 min).

 

When the car is in gear, clutch is disengaged, low or higher speed - the idle finds itself fine at at first, goes to 800rpm or so then starts to rise to about 1300 or sometimes a little higher about 1700. Stays there for a few seconds and then goes back to 800 and then after a few more seconds bounces back to 1700. It does when going slow in a parking lot and the same behavior even when going down hill at a higher speed. Kinda annoying as whenever you want to cruise around the lot, in 2nd, clutch in, the engine is jumping rpms a bit.

 

No codes, no pending codes. I just changed plugs, wires, PCV, and air filter and was hoping that this would do it. It seems to be unaffected by the power steering - doing this while turning the wheel or not.

 

Car drives totally fine otherwise. Only thing different is that the catalytic converter (changed by previous owner 10k miles ago) seems to do a lot of popping and sounds like it is really hot when I walk away from the car after parking it is quite audible. Always does this not just when I am "racing." The car is a PZEV. Not sure if cat was a PZEV one - but regardless car did not have this problem when cat was changed.

 

 

Since this occurs together with the action of the clutch I assume that it is some sort of sensor issue? Nothing to do with vacuum issues? Catalytic converter/ 02 issue and that is why it happens when it is hot?

 

Any advice is appreciated.

[heiche]

Might be clutch position switch.