Why is my van running poorly?

My 2007 Peugeot Expert van is running very sluggish. The problem is at its worse when running at a constant speed, with the van backing off then speeding up when accelerator is same pressure. I’ve had a diagnostics test carried out and also added some fuel additive with a new fuel filter, but still no joy. Do you have any ideas?

Asked on 6 October 2013 by gunnygugu

Answered by Honest John
Have you tried changing the air filter? If not that, might be the mass airflow sensor.
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