I own a Corsa c 1.7 DTI (Isuzu) engine which is having issues with boost.

Problem describe: When i start driving from 0 rmp to 2.5 is going very low.. After 2.5 rpms it will start getting as normal, but when it starts it gives a box with black smoke.

Things i have tried. 1. Maf sensor 2. Boost sensor 3. New Vacuums (n75) valves 3. Third turbo is currently on car, because first one was crashed while driving second one the same.

When i try to diagnose, using op-com, and Launch 431 pro, it wont give me any stored error code.

Using Launch diag, today i have tested n75 valve for egr which is ok, and n75 valve for turbo which is ok too.

(NOTE: Using launch you can test it with active inactive and pipes will start sucking air (vacuum)).

Today also we have removed Turbo, cleaned as well (but it was already looking cleaned) We changed new wastegate and tested to see if its closing enough to load the boost



  • Welcome to Motor Vehicle Maintenance & Repair! Mar 24, 2020 at 18:28
  • A common problem with turbocharged engines is lack of boost at low rpm. It's often termed "turbo lag" and it due to the fact that at low rpm there is not enough exhaust flow energy to spin the turbo fast enough to provide boost pressure. It also takes a while for the turbo to spin itself up. Is this a new problem or has it been this way all along?
    – jwh20
    Mar 25, 2020 at 11:46


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