What does it mean when I unplug a vacuum line and my idle doesn't change?
I'm having a small surge/gurgle in my idle which is annoying me to no end. My car has also decided that when I push in the clutch at anything over 2500 RPMs it goes full lean and the RPMs plunge, sometimes to only a few hundred, before it rights itself. This makes for rough driving and me having a mild heart-attack each time I see them plunge.
So, I have been reading and thought maybe the EGR was stuck open. When I unplugged the vacuum hose on top of it (to see what would happen), nothing changed about the car. There was some vacuum in the hose, but the idle note, RPMs and mixture didn't change.
So, I went to my throttle body and unplugged the driver's side vacuum hose. Again, nothing changed. There was a weak vacuum in the hose.
Then, I unplugged the throttle-body's passenger's side vacuum connection and the idle stumbled more and my mixture went lean (about 16.5-17).
I have a few questions:
1. If unplugging the driver's side vacuum hose did not affect the idle or anything about the engine, does that signify a vacuum leak? Or is that side on a different "path" and has no effect on the engine?
2. At idle my vacuum is about 22" (as measured by my boost/vac gauge, connected to the driver's side vacuum connection). When I disconnected the line leading to the throttle body, the vacuum dropped to 18". Is that normal? Also, would it be possible to have a vacuum leak and still pull this much vacuum at idle?
3. During this whole time of unplugging the EGR and all the vacuum lines going to my throttle body, I never once set off a check-engine light. What's up with that?
4. When I clutch in (especially after driving on the highway) the RPMs plummet to idle, sometimes even a few hundred RPMs below idle, before they catch themselves. It hasn't stalled yet, but my idle is raised 150 RPMs above stock so had it been stock it may have stalled. Does this sound like an EGR problem? A vacuum issue? Something else?
2001 Laser Red GT
Vortech V3-Si with 42lb Injectors (Tuned with Sniper SF)
Pro 5.0 Shifter, Flowmaster Super-40 Exhaust, Offroad H-Pipe