Engine will turn full RPM on startup,after a few seconds will idle but no RPMs,bogs out

Hi, this is Bo, an auto expert on RepairPal's Car Genius team! It sounds like your 1990 Mitsubishi Montero may be experiencing a fuel delivery or airflow issue. Since the Montero idles fine but loses power as soon as you try to rev it up, I'd look closely at the **fuel system and airflow sensors**. Even with new components, sometimes parts like the **mass airflow (MAF) sensor** or **throttle position sensor (TPS)** can need calibration or adjustment to work with the engine properly. A vacuum leak could also cause this kind of issue by disrupting the air-fuel ratio. Another suspect might be the **ignition timing**. If something’s off with the timing setup after the new belt installation, it could cause similar symptoms. Checking the timing is essential after installing a new belt to avoid misfires or low power. A diagnostic scan to check for trouble codes would also be helpful, even on an older vehicle like yours, to pinpoint any additional issues. If you need any further advice or want help finding a trusted RepairPal shop in your area, please feel free to call us at 877-913-1554.