Volvo Repair: 91 Volvo 940 Turbo, gate settings, volvo 940

Question
QUESTION: We are working on a 91 Volvo 940 Turbo and it is running rough and cuts out at higher speeds, we have looked at some different things but did not know if anything jumps out at you as obvious?

ANSWER: Ian, Is it running rough always or just higher speeds?  Under boost on just normal driving?  Roger

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QUESTION: Thanks Roger, It is running rough under boost.  Under hard acceleration it pops through the intake.  Thanks for your help,

Ian

Answer
Ian, Ive seen this before but cant remember exactly what it was. I would check to see if all turbo hoses are good and since you checked all other avenues, then I would check the waste gate settings as well as the vacuum diaphragm on the turbo. Im assuming its a Mitsu Turbo charger.  Other than that, I would have to go through the motions with scanning and tests.  Roger