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2000 Mitsubishi Eclipse: P0100 to P0107 to P0500 - Idle Issues and Diagnosis

Model: 2000 Mitsu Eclipse Fault Code: P0100 Posted: 2010-02-09 14:48

I was driving home from my girlfriend's house when the car suddenly died. All dashboard lights came on, and power steering failed. I managed to restart it, but as soon as I shifted into neutral (manual transmission), the engine stalled again. To keep the vehicle running, I had to continuously rev the engine. After restarting, I heard a squeaking noise and noticed rough idle—however, driving performance was normal. I took the car to Auto-Zone, where it returned a P0100 code (Mass Airflow Sensor Range/Performance Problem). I replaced the MAF sensor, removed an aftermarket 'gas saver' device previously installed in the intake manifold, and installed a new air filter. The service light remained on, but the car ran normally at that point. However, just two blocks from home, I made a sharp right turn and the engine died again—this time with all dashboard lights illuminated. Every time I try to idle, the engine stalls. I disassembled the intake system and cleaned the throttle body using carburetor cleaner. I thoroughly removed debris from the throttle plate. Afterward, the car began throwing a P0505 code (Idle Control System Malfunction). My question: Could installing a new cold air intake resolve this issue? Or is there another underlying cause I should investigate? I'm looking for reliable troubleshooting steps to fix both the idle issues and the persistent fault codes.

Related fault codes
P0100P0107P0505
Comments (3)
Anonymous 2010-02-09 17:24

Even after cleaning the throttle body, the engine still won't hold a steady idle. A cold air intake is unlikely to resolve your P0100 or P0505 issues—it may even worsen them. I recommend checking for vacuum leaks and ensuring you cleaned both the throttle valve and its surrounding passages during maintenance.

Anonymous 2010-02-09 21:10

Yes, when cleaning the throttle body, I also cleaned the flap and valve on both sides. I suspect a vacuum leak exists but don't know how to properly test for it. Can you recommend where or what to check first? Also, my car's P0505 code specifically indicates an idle control system malfunction.

Anonymous 2010-02-10 06:14

There’s a common guide on this forum about detecting vacuum leaks. Try using a can of throttle body cleaner and spray it near hoses, gaskets, or connections while the engine is running. If the idle speed fluctuates when you spray, that's a strong indicator of a leak—then focus your inspection there.