Mitsubishi Repair: Surging idle, mass air sensor, throttle position sensor

Question
I have read through a lot of your responses to other questions and hope this isn't repetitive.

First off when the car is first cranked it idles really high around 3500-4000RPM and the belts squeak.

Once the car is put in REVERSE or DRIVE then the RPMs go down to 1200.

Originally the car would surge violently while stopped, rocking the car forward. Then when driving as long as my foot was on the accelerator the car behaved normally, but once I let off between speeds of 25-40mph the car surged.

Then I discovered that a small hose about 5/8" in diameter was disconnected from the manifold. I think it runs from the fuel injectors to the oxygen sensor (but definitely not sure).

So once I connected that hose back and the car's surging lessened.

So I could you tell me a some things to do in order of most likely to least likely?

I.E. - EGR valve, Mass Air Sensor, Throttle position sensor (TPS), fuel pump, alternator, throttle body, and all your intake and vacuum hoses

I saw something about a leak-down test. How is that performed?

Could you tell me the details for checking my ISC or IAC? (Is there a difference in these two?)

I know these are a lot of questions. I would be glad to compensate for a thorough answer.

Thanks

Vance

Answer
Vance this sounds like an ISC IAC problem its located behind/side of throttle body, vacuum hoses can cause idle problems and surging. Replace the ISC if you take it off and you cant push in the spool by hand or if its hard to move.  Check vacuum hoses diagram under the hood for reference...all this is if you have a 95-99 eclipse! Any engine codeslights?? You can read your own codes....I have included a website that can help you pinpointing problems and troubleshoot must have!



http://www.2gnt.com/nuke/modules.php?name=Sections&op=viewarticle&artid=8


Good Luck!