A Vauxhall Insignia 2.0-litre arrived with an idle fluctuating between roughly 800 and 900 rpm. Live diagnostic data was recorded and the engine was monitored during treatment.
What was observed
After around 20 minutes the engine was reported to have quietened. At roughly 40 minutes it sounded more responsive, followed by post-clean checks.
What it does not prove
One treatment cannot prove that carbon cleaning fixes every rough idle, restores a set amount of power or cures a damaged component. An engine clean can only clean; it cannot repair broken, worn or failing parts.
The lesson
Carbon cleaning is most credible when it sits inside a proper process: visual checks, an OBD scan, monitored treatment, a test drive and final diagnostics. Expectations should come from the vehicle’s condition—not a miracle claim.