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Discussion Starter · #1 · (Edited)
2012 Lancer EVO X.
Stumbles at idle, sometimes stalls.Lack lack of power, stumbles when snapping throttle.

Verified fuel pressure ok @ 45 psi idle
Inspected plugs, appear ok, no cracks in porcelin, clean, no fouling or signs of running lean/ rich, no carbon tracking.
Drained fuel tank and put in fresh fuel, Removed fuel rail, inspected injector tips all appear ok.
Disconnected and plugged purge valve line.
Removed OEM bypass valve and plugged, verified vac source 15 inches of vac at idle.
Performed boost leak test, and smoke tested intake system no leaks present.
Happens with Air conditioning on or off, Rad fan running or not, Vehicle hot or cold.
Engine coolant temp PID is accurate, so is intake temp.
Has a COBB tuner, have returned to stock and re tested, same concern.
Have unplugged both MIVEC phaser solenoids.
Fuel trims cycling around +/- 5
145 PSI compression on all cylinders.
Injectors OHM out to 13 ohms.
Has an ETS intake.
Bringing it up off idle it runs a bit better, doesn't stumble as bad.
If I disconnect the charge air cooler piping or the intake tube at the throttle body it gets WAY better. Stumbles but very minimal.

Throttle body, MAF, MAP have all been replaced. Sent it to Mitsubishi came back with $1600 bill, they put bank 1 sensor 1 O2 sensor in it, then said " we had our 20 year master tech on it for hours and he has no idea try disconnecting the aftermarket radio and turbo timer. (turbo timer is built into Compustar remote start)

 

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2011 Evo X MR
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Questions for clarification:
  • In the video, are you messing with the throttle or is it doing that on it's own?
  • When did it start, and when it started, did it happen all of sudden or slowly... what triggered the behavior?
  • Are there any codes?
  • How does throttle body position compare with commanded position in OBD scanner?
  • If you reset the ECU via cobb accessport, does it do it right after the first start? And if you hold your foot on the gas so it's around 1500 rpm, is it stable or does it oscillate?
 
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