[Crystalk98]

I have a Hyundai i30 2014 which I took for a service a week ago. Since picking up my car there has been issues while I’m driving, such as when I accelerate, the car starts making a bad noise while my foot is on the accelerator and the RPM and Kms struggle to go up. I have noticed it’s even worse trying to go uphill as well and it’s the worst when I go to take off after stopping at a red light.. when my car is parked and in neutral and I accelerate it’s just fine, but the issue happens while I’m driving. I have been to 3 mechanics including the one that did my service plus an exhaust specialist and auto electrician and no one can figure out the problem. No warning lights come on and no issues were found when performing a diagnosis

[The Gonz]

That one's a real poser, Crystal. 
I hope someone here can recognise the symptoms and advise soon.

[Shambles]

Hi Crystalk98 and 

Given your explanation I'd be tempted to ask for a check on the Mass Airflow Sensor (MAF) - have a read here and see if you spot anything you recognise.

[Aye30]

Hi, what exactly was done in the recent service? New plugs, filters, fuel treatments?  And can you hear any stuttering, at idle, from the exhaust? Also does the power loss start at a specific  rpm, and does it pickup at all given enough time?

[Lorian]

Check the spark plug leads are sound, check for blue sparks and clicking when idling (helps if its dark out)
Petrol filter (wouldnt make noise)
air filter box (would make noise but not such a drop in power)
Fuel pump/relay - could make noise and reduce power

what sort of noise is it?