XC90 V8 - Engine missing under light load

Hey team, No I have not got back into a Volvo but one of the guys that I know has a V8 XC90. Only has 140k on the clock so engine is realtively fresh. He bought it around yesterday to put the Vida on it because it has been playing up. No codes of any note other than the CD changer playing up.

I took the thing for a drive and there is a very noticable miss (I will use this term because that is what it feels like I have not confirmed this to be the case) It happens between 1500-2000rpm at light load. It is not speed dependent because I could get it to happen at various speed just as long as the engine rpm remained constant.

I plotted things like A/F ration and ignition timing but there was no significant change which makes me think that it was not a miss as the A/F ration should have changed but didn't. Both banks tracked the same and seemed stable.

I have told the owner to check the plug on the Throttle Body and to give the MAF sensor a clear with sensor cleaner. I suggested that pulling a plug might be a good idea to see if and when they had been changed.

Given that it is under light load I would almost put it down to issues with fueling but nothing showed up.

Also of note is that when I was sneaking it up to the required rpm it would start to surge about 150-200rpm before then holding rpm steady and starting to "miss". I am out of ideas so thought I would engage the brains trust. Gearbox is good and happy. Is there any other sensors that might be causing the issue but not throwing a fault?




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