Idle Changes When Depressing Clutch Pedal?

[Thoughtful_One]

I have always had this problem and am unsure as to why it would happen. The clutch hydraulic-system is not vacuum assisted, correct? (Mechanical pedal -> Clutch MC -> Hardline -> Slave). When pressing in clutch, the idle speed will increase by 2-300 RPM. Also, at idle, when pressing the brake pedal, the idle also increases (vacuum leak?).

Lastly, when adjusting/calibrating the TPS, does the timing have to first be correct? I recall last year when I had some work done at a shop, they adjusted the idle without the TPS disconnected. How do I compensate for this? My idle has been been strange ever since I have had my car.

[jdm_master_X]

idle raises when you depress the clutch because you are disengaging the transmission from the motor, hence the rise in idle. rise in idle = less load. same goes for braking, because you are drawing vacuum via brake booster. any load on the engine (alternator, PS pump, AC) will mess with idle speed, and the computer should compensate for such a load.

if its a massive drop in idle where it feels like its going to stall out, then a leak in vacuum maybe a cause (assuming its brake related)

[Thoughtful_One]

Yes, this makes sense, but depressing the clutch in NEUTRAL causes the idle speed to change. Isn't the engine disconnected form the trans. in neutral?

[i2ice4m3]

the only way the engine and transmission aren't connected is if you disengage the clutch

[Bronze MFP]

even though the transmission is in neutral its still spinning the gears in the trans, sounds strange i know, but go to http://www.howstuffworks.com and read how a manual trans works and all will be answered

edit: for the lazy: http://auto.howstuffworks.com/transmission.htm
Modified by Bronze MFP at 3:24 PM 12/27/2006

[Thoughtful_One]

I thought about it before and answered my own question ... makes sense. Thanks for the help.