Weird symptoms

[The Sorrow]

Basically my Eclipse randomly begins to rumble while driving. Then tonight i was stopped at a stop light and i was in neutral idling, the rpm would drop to around 500 then jump to 1k or 1500 and drop again like it was about to die then came back to life. Also when i shift gears there's a small bump sound. I'm guessing either transmission or clutch, leaning toward transmission. Any help guys?

 

[concept4g63]

I would say check your sensors and probably some seals on the th, maybe the biss screw as well. I'm not familiar with your setup bit yea check them and goodluck

 

[spower]

oxygen sensor is a good place to start. invest in a voltmeter

 

[The Sorrow]

A sensor would make sense....most of this started happening after i filled the tank with regular...i had a tank of premium before.....maybe the fuel switch?

 

[Eternalsolitude]

I would first clean your throttle body (carb/throttle body cleaner from auto parts store and rag) Make sure there is no carbon buildup where the plate sits closed.

Next step I would add a can of SeaFoam to a topped of tank of premium gas. Run it through and see if your issue still persists.

Any check engine light/ OBDII codes?

 

[The Sorrow]

Actually...I've had the check engine light on for a while, just haven't had a chance to get it serviced. I'm also quite sure its due for an oil change. Gonna have to do that too. Speaking of oil, any particular type? I hear that new synthetic stuff is good.

 

[Talon tsi PR]

Clean the throttle body with carb cleaner and check the idle speed sensor

 

[The Sorrow]

Quick update. Did an oil change and swapped out the TSi ecu for the non chipped GS-T ecu. The ecu swap helped the reving on idle and the oil change reduced the banging during shifting quite a bit.

*UPDATE*

The mount bolts on the front and rear motor mounts were gone, so the engine was rocking back and fourth. That was most of the rattling. We swapped them for some grade 8 screws for temporary until we order the bolts from Mitsubishi. Other than that i found out that the cam sensor isnt the corect model and the ECU is not tuned. Its running much better though. Other than the RPM fluctuating from 1k to 1.5k when i start it cold its going great.